4 Ecosystem Processes: Community Dynamics
(Part 2)
4 Ecosystem Processes: Community Dynamics
(Part 2)
Life to the Full
The previous section of Part 1 discussed the first of two methods utilized to create an ecosystem that is not susceptible to domination by pests, disease and weeds. That method can be summarized by one word: death. Hopefully by now you understand that this strategy is untenable in the natural world, even though most farmers and ranchers are taught to sterilize away the bad guys like they’re working in some sort of closed operating room. So, what’s a producer to do? It’s simple. Rather than killing our way to health, the best solution to many, if not most, of the laundry list of issues that agriculture faces today is to do a total 180° turn and promote as much life as we can. Only by implementing management systems that promote a rich diversity of life can agriculture reap the benefits of succession and efficiently manage our role in climate change, soil erosion, food prices at the supermarket, nutrient density of food, water quality, air quality, worker’s rights, animal welfare and rural development while ensuring producers make a livable wage. Creating and maintaining a diversity of living organisms on the farm and ranch ensures that there are appropriate checks and balances in the system that prevent domination by a few opportunistic organisms. In addition, each and every living organism on Earth brings a unique skill set to the table, meaning a wider range of ecosystem services are provided when species richness and diversity improves. Compare these positive compounding and cascading effects to the negative side effects listed during a pharmaceutical commercial or the skull and crossbones on the label of a pesticide, and you can see a clear contrast in the consequences of conventional and regenerative systems. In fact, encouraging as much life as possible is so fundamental to the ethos of regenerative agriculture that diversity is the only topic that is a Principle of Soil Health, a Rule of Adaptive Stewardship and an Ecosystem Process.
To illustrate this point, let’s return briefly to our discussion on C. diff . Recall that a wiped out gut microbiome is a major risk factor for developing an infection of this potentially deadly bacteria. With this in mind, medical professionals hypothesized that a speedy recovery from C. diff infection would be observed when a patient’s gut microbiome returned to a rich and diverse state. Lo and behold, the treatment worked and fecal microbiota transplantation (FMT), also known as stool transplantation, was borne out of this hypothesis. FMT, for those that don’t know, is a procedure in which stool from a healthy donor is placed into the gut of a patient in order to treat a certain disease. The healthy patient’s stool acts as an inoculant of healthy microbes, greatly speeding up the recovery of the patient’s gut microbiome to a healthy level. Put in the context of succession, FMT allows for a speedy return to a disease-resistant climax community. Incredibly, FMT has a cure rate of 80% to 90% with a single treatment and is now the standard procedure for preventing recurrent C. diff infections.87 The results of FMT are almost unbelievable, but it makes total sense inside the broader discussion of succession and ecology. That’s the power of working with nature and not against it!
C. diff’s r-strategist tendencies and FMT’s success may seem too-good-to-be-true, but it’s actually the way the natural world operates. Richness and diversity of species naturally bring about health and balance. Life is pretty simple in that way, and land managers have a lot to gain by prioritizing richness and diversity in the agricultural ecosystems they take care of. Earlier sections discussed the problems that arise when microbial, insect and plant communities are disturbed, so let’s now look at the potential benefits when we build them up, starting with the microbiome in the soil.
Underneath our feet is an eternal battle raging between trillions of microbes as they collaborate and compete for precious resources. Grandpas worldwide might say they’re “old as dirt”, but this microbial war for space and food has truly been around since the genesis of dirt. (Soil for you purists out there!) The point is that this battle keeps populations of potentially harmful species in check and greatly reduces the risk of a few aggressive ones dominating resources to the detriment of all the others. Scientists even have a term for a soil with these qualities. They call it a disease suppressive soil, or DSS. How awesome is that? The soil is naturally suppressive of disease when the system is operating as it was designed. The key to it all is the biology. As one group of scientists write, “Maintaining a dynamic microbial balance between species, high soil microbial biomass, and high microbial diversity are key factors which facilitate the development of disease suppressive soil (DSS).”88
So, how do they do it? How can tiny organisms possibly do a better job at suppressing disease outbreak than the powerful chemicals inside of pesticides that are back by billions of dollars of research and development? Not to sound like a broken record but it boils down to diversity. To understand this more fully, imagine yourself as a root pathogen in a rich, diverse soil environment. If you were to do this, you’d find yourself in a bustling metropolis of activity like nothing you’ve ever seen! Life is moving at incredibly fast speeds, and you soon discover that all kinds of organisms lurk around every corner that 1) make chemicals that will harm you, 2) are bigger than you and want to eat you, 3) are smaller than you and want to colonize you or 4) get in your way as you try to find food and shelter. You can see how difficult it would be for you and your family to find a susceptible plant root and multiply fast enough to do large-scale damage with this kind of competition. The microbial community is simply too numerous and too powerful for you to get a stranglehold on the situation. These are the direct and indirect methods in which soil microbes keep pathogens at bay. In scientific, smarty-pants terms, we would say that beneficial microbes inhibit soil pathogens through various modes of action, such as “antibiosis, parasitism, competition for resources, and predation.”89 The diversity of methods is the true source of strength!90 If one mode of action doesn’t keep a pathogen in line, something else likely will. As a result, pathogens are unable to become resistant to holistic biological suppression like they do with pesticides. There are simply too many modes of action for a microbe to change quickly enough to evade them all. To make matters worse for pathogens, beneficial microbes themselves have the ability to quickly shift and adapt to new pathogen strategies. Contrast this with pesticides whose chemical structures are the same, predictable pattern, making it easy for pathogens to sidestep it in the future. It’s no wonder that resistance to such products has become a widespread issue, especially because pesticides often only use one or two modes of action to control pathogens.
Rather than rely on chemicals, we should start fighting fire with fire and rely more on fellow members of the soil microbiome to do our bidding for us. To achieve disease-suppression levels, farmers and ranchers need to implement practices that promote organisms like actinomycetes91, azospirllum92, Pseudomonas fluorescens 93 and the hundreds of other species that hinder plant pathogens through the production of antimicrobial compounds such as “siderophores (metal chelators), ß-1, 3-glucanase, chitinases (fungal cell walls are made of glucans and chitin), antibiotic, fluorescent pigment and cyanide”.94
One point worth noting is that plants are active participants in designing a disease-suppressive soil microbiome. They are able to sense danger and exude chemical compounds that attract microbes to the rhizosphere to take care of dangerous microbes (and other pests like insects).95 One German study does an excellent job of detailing the interplay between plants and microbes to suppress pathogens, which in this case are disease-causing nematodes. Just to show how complicated these interactions are, here is the description from the authors: “We highlighted nematode biocontrol mechanisms, especially parasitism, induced systemic resistance, and volatile organic compounds using microbial consortia, or bacterial strains of the genera Pasteuria, Bacillus, Pseudomonas, Rhizobium, Streptomyces, Arthrobacter, and Variovorax, or fungal isolates of Pochonia, Dactylella, Nematophthora, Purpureocillium, Trichoderma, Hirsutella, Arthrobotrys, and Mortierella.”96 That’s a lot of moving parts, but it in all honesty it’s probably just a fraction of what’s going on down there! In fact, suppression of pathogens is only half of the story. Soil microbes also work hard to strengthen plants and make them less susceptible to a pathogen attack that got past the first lines of defense. They do this because roots and root exudates are the primary source of raw material and energy inputs into the soil, so it’s in the best interest of the soil microbiome to keep plants thriving and photosynthesizing efficiently. One well-studied group of microbes that aid plants are the “plant growth-promoting rhizobacteria” (PGPR). These bacteria can be found outside the root in the rhizosphere and in the plant root to provide protection from the inside.97 PGPR provide many services that lead to healthier plants, such as the production of beneficial plant hormones like auxins, cytokinins, gibberellins, ethylene and abscisic acid. PGPR also promote healthy plants by activating plant immune system responses (a.k.a. induced resistance)98, fixing nitrogen, solubilizing mineral phosphates and other nutrients for uptake and enhancing resistance to stresses like drought and high salt levels.99
Each PGPR has its unique skill in suppressing pathogens and strengthening the plant, which is great, but research shows that their effectiveness and reliability increases dramatically when they work together. For example, only the co-inoculation of Pseudomonas fluorescens F113 and Stenotrophomonas maltophilia W81 protected sugar beet from Pythium-mediated damping-off in an Irish field experiment compared to individual inoculation.100 Similarly, the co-inoculation of Pseudomonas fluorescens sp. M23 and Bacillus sp. MRF significantly decreased infection of Fusarium spp. in maize in comparison with untreated control plants and with a single bacterial agent treatment.101 Lastly, a field experiment in Thailand found that “the mixture of Bacillus amyloliquefaciens IN937a and B. pumilus IN937b elicited systemic resistance, leading to more consistent broad-spectrum pathogen control in various crops under field conditions in comparison with an individual strain.”102 If research shows improvements in plant health with the interaction of just two species of bacteria, just imagine the effectiveness of a rich, diverse soil microbiome with millions of species and trillions of viruses, bacteria, fungi, protozoa and nematodes all working in synchrony!
Speaking of fungi, just like there are PGPR, the soil is littered with various plant growth promoting fungi (PGPF).103 Fungi were discussed earlier in the article for their essential role in building soil macroaggregates, so we already know one way in which they improve plant health and promote succession. Mycorrhizal fungi are especially important in this aggregate-building process, but these root-associating fungi do much more than just build soil. Mycorrhizal fungi also boost plant health by increasing the uptake of water and nutrients like phosphorus, nitrogen and zinc, while also increasing a plant’s tolerance to adverse conditions such as drought, high temperatures, salinity, and acidity, or a build-up of toxic elements in the soil.104. In addition, mycorrhizal fungi stimulate immune responses in the aboveground portions of plants and make them more resilient against pathogenic microbes or insect pests.105 If that wasn’t enough, plants can utilize shared fungal networks to send warning signals to nearby plants so their neighbors can raise their defenses against an attack before it reaches them.106 Many people call this connection the “wood wide web” due to its discovery and presence in forest climax communities.107 Given all these benefits, it’s no wonder approximately 85 % (˜340,000 species) of all plant species are colonized by mycorrhizal fungi (˜50,000 species)!108
As great as mycorrhizal fungi are, not all PGPF are mycorrhizal. Trichoderma are a genus of soil fungi found all over the planet that are a model example of non-mycorrhizal PGPF. These ubiquitous fungi are known to increase plant healthy by “improving plant growth and vigor and enhancing stress tolerance, active uptake of nutrients and bioremediation of contaminated rhizosphere, as well as providing plants several secondary metabolites, enzymes and plant regulating proteins.109,110 The first image below is from Cornell University and shows the drastic improvement in root growth from sweet corn and soybean plants inoculated with a strain of Trichoderma fungus called T-22. The second image below was taken during my research at Purdue University studying the effects of T-22 on tomato plant disease resistance and production. Notice the difference in growth from the seedlings on the left that received a liquid inoculation with Trichoderma with the seedlings that did not .
Check out this article on Trichoderma from Cornell University for more detailed information on these superheroes in the soil.
In addition to bacteria and fungi, soil organisms like protozoa and nematodes benefit plant health primarily by cycling nutrients efficiently and controlling pathogen populations through predation. Viruses provide a similar service, except they operate through parasitism as non-living entities. By the way, if all the viruses on earth were laid end to end, they would stretch for 100 million light years112, so they’re obviously providing useful services that keep the system moving along or we would all be in trouble in a hurry! To read more about the benefits of protozoa, nematodes and viruses, check out the previous article on the Nutrient Cycle. Lastly, even archaea, the most forgotten-about class of microbes, promote plant growth, adaptation to abiotic stresses, and immune activation.113 It’s truly incredible how collaborative the natural world is.
Alright, so a thriving microbiome keeps pathogens in check and helps to create healthier plants. The question now is how to build up a degraded microbiome and reap the rewards that diversity offers? The short answer is to follow the 6-3-4! The longer answer is to implement practices that create a diverse habitat to support a diverse population of microbes. Build diversity and diversity will come, essentially. All kinds of microbes exist in the soil and each of them thrive in varying conditions. For example, some microbes require oxygen and some really struggle in the presence of oxygen, such as nitrogen-fixing rhizobia or many beneficial actinomycetes. Some microbes are small and can fit in tight spaces, while others are quite large and need bigger structures to roam around and find their food. In a nutshell, we’re trying to create heterogeneity by forming a well-aggregated soil that contains aerobic sites, anaerobic sites, tiny sites for prey, even tinier sites for organic matter to hide for decades, wide open sites for predators and hotspots of nutrient and water availability. This is the type of heterogeneity we’re looking for, but it requires proper soil structure!
The best way to encourage the formation of aggregates and heterogeneity is to allow the ecological system to do the work. Soil ecosystems will naturally self-organize, self-heal and self-regulate into increasingly efficient systems when they’re given the right conditions. I encourage readers to dig into a nearby fenceline (assuming it hasn’t been mowed too often), grassland or woods to learn what the soil used to look like in your region. This is called your “ecological historical context” and it’s likely how your soil would look given the chance to heal itself. One of the best ways to start this healing process is to ensure there is a good home for the underground herd who will be doing the majority of the work. As it turns out, living roots create an extremely hospitable environment for soil biology, and the area immediately surrounding roots, called the rhizosphere, is considered one of the most complex ecosystems on earth.114 This flurry of biological activity sets in motion the soil building process. For example, roots and the mycorrhizal fungi work together to physically anchor the soil and glue soil particles together into macroaggregates.115 Therefore, step one to creating a soil that is fertile and abundantly productive is to get plants growing in the soil. No ifs, ands or buts about it. Once living roots are in the soil, disturbances like tillage and pesticide applications also need to be limited so the roots can establish themselves and the biology has time to work off of them. Chronic tillage, in particular, is harmful to the building of soil structure because it breaks apart macroaggregates and creates the homogeneous conditions that discourage diversity.116
As any good parent (hopefully) knows, it’s not enough to just house the living organisms under our care. We’ve also got to make sure they’re constantly fed, and microbes are no different. They require constant inputs of food to use as they live, grow and reproduce. Step one to feeding soil microbes on a large scale is to make sure living roots are in the soil for as many days of the year as possible. It’s déjà vu all over again! First and foremost, root exudates are a major source of food for microbes in the rhizosphere.117 Yes, these organic compounds are strategically released by plants to recruit certain beneficial microbes118, but it’s also believed that the majority of root exudates are passively lost from the root.119 Regardless of how they got there, microbes happily consume all shapes and varieties of exudates, which includes “low molecular weight primary metabolites (especially sugars, amino acids and organic acids) and secondary metabolites (phenols, flavonoids and terpenoids)”120 Soil microbes also rely on plant roots themselves as a direct source of food. Decomposing microbes (a.k.a. saprophytes) happily feast on roots as they are dead and dying, whether it be short-lived root hairs or sloughed off root cap cells.121 An added bonus to saprophytic feeding is that underground decomposed material is turned into soil organic matter much more efficiently than decomposed aboveground residue.122
Drastic management changes like utilizing cover crops and minimizing tillage should be done at the appropriate pace. What is “appropriate” differs on each farm and ranch based on differences in context, such as climate, social pressures and financial constraints. Whatever pace you decide to take, don’t expect changes to happen overnight. Ecological degradation of a field or pasture didn’t take a year to happen and neither will the recovery. That’s not meant to discourage you, but it’s a reminder that these things take time. Even so, producers often see major improvements in soil structure when given a few years of little to no disturbances and consistent inputs of food into the soil system, which is almost unbelievable when compared to geological timescales that think nothing of a thousand years. For us to positively influence soil structure in our lifetime and move along the succession timeline, we’ve got to create a soil that works on biological timescales. Getting living roots in the soil is the best way to kickstart that transition. The initial improvements brought about by living roots sets off a chain of positive feedback loops similar to those found in thriving climax communities. As the soil begins to self-regulate into macroaggregates, microbiome richness and diversity increases123, which leads to an increase in plant health and diversity, which in turn significantly increases bacterial and fungal biomass.124 Farming and ranching becomes really fun when biology is truly in the driver seat because the system is able to produce abundantly and improve itself while doing so.
Aside from the gold standard of living roots, another useful way to feed soil microbes is to add external amendments like compost. Compost is made up of organic matter in various stage of decomposition and the microbes that have already begun to decompose it, which makes it agriculture’s version of a probtiotic and prebiotic rolled into one! In essence, properly made compost provides a fresh regimen of beneficial soil dwellers, especially fungi and prokaryotic organisms (bacteria and archaea), as well as the food and shelter they need to help them survive in their new environment.125 Consequently, compost has been shown to improve crop productivity 126 and build disease suppression in the soil as a result of its application. 127 My own research project yielded similar results as the the survival rates of Trichoderma T-22 organisms increased significantly when applied to plots amended with a fungi-rich deciduous leaf-based compost in the field. In addition, tomato plants that received the compost and Trichoderma inoculation exhibited fewer foliar disease symptoms and produced significantly higher tomato fruit yields.128
What about composted plant material that drops out of the rear end of an animal? Not many people think of manure as compost but that’s essentially what it is. Think about a grazing cow that consumes a mature plant in the pasture. The digestive system of the cow and the microbiome contained within it break down that plant material and transform it into a beneficial soil amendment in a matter of days. This is a lightning fast cycling of nutrients back into the soil ecosystem compared to the months it would take for a standing plant to degrade on its own. Adding insult to injury, plants left standing will return fewer nutrients to the soil ecosystem because much of the nutrition will oxidize away by the time the plant hits the soil surface. Oxidized plant material may be a decent source of carbon, but that’s about all the soil is getting back.
Manure is also an excellent source of beneficial microbes and organic matter to feed soil organisms. An incredible 18-year studying examining the application of pig manure found that manure application significantly enhanced soil bacterial diversity and the relative abundance of saprotrophic fungi which was observed to suppress plant pathogens and parasites.129 Another study found that manure treatments significantly increased the proportion of soil macroaggregate fraction under the high level manure treatments compared with low manure and no manure treatments. As a result, the total number of nematodes increased significantly, which directly benefited carbon cycling in the soil primarily by grazing local bacteria.130 So, what we really have in manure is an organically produced fertilizer/probiotic/prebiotic/Fecal Microbiota Transplant soil amendment that helps build the house for soil microbes and also feed them. What can’t poo do?
Now that we’ve examined how diversity in the soil promotes health and wellness, it begs the question: does the same pattern reveal itself aboveground? Specifically, do regenerative practices encourage succession through plant and insect species diversity and, if so, what kind of benefits can producers expect? Let’s answer these question by breaking it down into grazing and cropping sections. We’ll start with livestock operations that utilize adaptive multi-paddock (AMP) grazing techniques and finish with cropping systems that prioritize regenerative practices like cover cropping and reduced tillage.
Succession on the Ranch
By prioritizing recovery and rest, AMP graziers are allowing their forage to improve at the speed of nature. One input that often becomes useless after implementing AMP grazing is fertilizer. Yes, fertilizers green up a pasture and promise a shortcut to production, but there’s a very high probability that it’s doing more harm than good. Speaking specifically about nitrogen fertilizer, professors Brady and Weil describe the unintended consequences of its application in their textbook, The Nature and Property of Soils. They write, “Natural rangeland ecosystems contain a wide variety of native plant species that are known for their ability to conserve nitrogen and efficiently utilize low levels of deposited nitrogen (2–5 kg N/ha/yr). However, research using deliberate nitrogen additions suggests that as nitrogen deposition increases, certain plants—often exotic species—that are highly responsive to high levels of nitrogen quickly crowd out many of the desirable native species that are adapted to grow efficiently at low nitrogen levels. Attempts that have been made to increase rangeland productivity by adding fertilizer nitrogen may increase productivity temporarily, but again, the low-nitrogen-requiring native species are soon crowded out and replaced by high-nitrogen-requiring exotic species that are generally considered weeds. The resulting systems are lower in biological diversity and productivity than the original native rangelands.“131 Therefore, one of the most effective questions to ask ourselves is, “What do I want my pastures and my forage to look like?” This little exercise is essential for two reasons. First, it requires the grazier to picture an ideal pasture for grazing. Once this is done, having a visualized goal allows management decisions to become more obvious over time. Just like a GPS demands a destination to give a route, we have to have a target to aim at in order to confidently know the path forward. Another popular way of saying it is “managing for what you want”. Always ask “What do I want?” and follow up with “How do I get there?” Remember, if you fail to plan, you plan to fail. Alright, enough cliches. The rest of this section is filled with information illustrating why graziers should aim for a pasture that mimics natural climax communities full of plant and insect diversity and why AMP grazing is the ideal route to get to that (now) desired destination.
The first reason to manage for diverse grazing land is that plant species diversity and diversity within each functional group (grasses, forbs, legumes, woody species) increases aboveground community biomass production.132,133,134 That’s quite the mouthful. Essentially, more types and species of plants will produce more plant material than fewer types and species of plants. One meta-analysis found an average of 1.43 times more plant material in the most diverse polycultures compared to the average monoculture.135 A 9 year study from Penn State University found similar results when comparing a two-species mix to a five-species mix over a nine year period. When averaged across years, the five-species mixture produced 31% more forage biomass than the two-species mixture, and the difference between mixtures tended to be greater in wet than in dry summers.136 The study also found the five-way mix increased soil carbon levels faster in the top 100 cm depth compared to the two-way mix: 1.80 Mg ha−1 yr−1 for the five-way mix compared to 0.50 Mg ha−1 yr−1 for the two-way mix. This increase in soil carbon indicates a subsequent increase in organic matter, which is key to improving overall ecosystem functioning and services.137 While these results are encouraging, research dedicated to the effects of AMP grazing are showing even more promising results for pasture diversity and productivity. The following are a few such results:
- This analysis suggested the reference natural areas (RNAs) were by far more diverse with more species sharing the Importance Value. It also suggests conventionally grazed (CG) ranches were the least diverse and that AMP ranches were transitioning (“diverging”) toward a higher dominance diversity condition, away from the CG plant community.138
- Standing crop biomass was >300% higher on AMP ranches compared to conventionally grazed (CG) ranches.138
- On average, the AMP ranch had 1.5 more species per grid than the CG ranch, with the maximum richness of six, as compared to four in the CG ranch. (Meaning that AMP encourages diversity and mixing of species in close proximity, while CG grazing encourages big clumps of homogenous species.139
- AMP grazing systems outperformed CG systems by generating: (a) 92.68 g m2 more standing crop biomass (SCB), promoting 46% higher pasture photosynthetic capacity, while observing a 19.52% reduction in soil C (CO2) respiration rates.140
- Net above ground primary production (NAPP) was nearly three times higher in muli-paddock (MP) pastures than in conventionally managed (CM) pastures and seven times higher than in hayfields at the time of sampling.141
- Our review revealed that biodiversity, nitrogen cycling, and carbon storage in regenerative grazing systems more closely resemble wild grazing ecosystems than do conventional grazing systems.142
Diversity and plant production are great results in and of themselves ecologically speaking, but the ripple effect of a regenerated pasture is also staggering from a business standpoint. Financial research is difficult and quite scant at the moment, but initial findings indicate drastic increases in forage production from AMP grazing provides a direct avenue to increase livestock numbers sustainably and increase profitability.
- Multi-paddock (MP) grazing excels in that it can sustain much higher stocking density without a negative influence on the biomass and composition of grass.143
- AMP managed systems provided sufficient forage biomass to support grazer stocking densities 2.38 times higher than conventional grazing systems, while also promoting development of soil food web structure, diversity and functionality and collectively making AMP systems more ecologically resilient, sustainable and profitable.140
- Simulations show that shorter periods of grazing increase both ecological condition (EC) and profitability while increasing recovery periods increases both EC and profitability initially but profitability decreases if recovery periods are too long. Both EC and profitability are positively related to number of paddocks used.144
- Plant diversity substantially increased quality-adjusted yield and revenues. These findings hold for a wide range of management intensities, i.e., fertilization levels and cutting frequencies, in semi-natural grasslands.145
Another benefit that diversity of plant species brings is an increase in nutrition offered to livestock. This results in healthier livestock and less money spent at the vet. As humans, we’re told to “eat the rainbow for good health” because specific colors are made by the presence of specific compounds, such as the anthocyanins that give blueberries their blue hue. If that’s the case with us, why wouldn’t it be the case with animals? The fact is that it’s the exact same for livestcok, and diverse pastures are part-restaurant, part-pharmacies that allow an animal to select for forage containing the nutrients they require at that moment in time. Dr. Fred Provenza of Utah State University describes this as allowing animals to express their “nutritional wisdom”. I encourage everyone to read his masterpiece Nourishment to learn more about nutritional wisdom of livestock and humans. Inside, you’ll find a satisfying mixture of decades of research and old-world wisdom that depicts how livestock are capable of self-medicating when given the chance. A diverse pasture is not only composed of a mix of macronutrients (carbohydrates, fats and proteins) but it also means there are a plethora of plant secondary and tertiary compounds, which are produced by plants as mechanisms to survive stress in their environment. They are generally involved in processes that improve health and wellness of the plant rather than direct growth and development. Fortunately, many of these compounds are beneficial to us and livestock when they are consumed. Tannins, glycosides and flavonoids are a few common examples. Benefits of plant secondary and tertiary compounds for livestock include antiparasitic effects146, antioxidant effects147 and increased protein and energy efficiency.148
More than that, the combinations and interactions between nutrients provide benefits in the bodies of living organisms. For example, sheep and cattle can consume a significantly greater amount of endophyte-infected tall fescue when they first dine on plants high in tannins such as birdsfoot trefoil or sanfoin. The tannins bind with toxic alkaloids from the fescue in the animal’s digestive system, making them much less harmful.149 Tannin consumption also allows livestock to consume significantly more sagebrush, which contains high levels of terpenes.150 Don’t know which plants contain these compounds? This is yet another reason to manage for a diverse pasture and hedge your bets! Livestock will learn to eat a much wider variety of plant species to find the right synergies between nutrients, especially when their mothers are there to teach them from a young age. This includes many of the “weeds” that show up in our pastures. Many of the forbs we call weeds have deep taproots that bring health-promoting mineral nutrition to the surface, so rather than curse them, AMP graziers train livestock to consume weedy species for the nutrition contained within them.151 Similarly, trees and other woody species are sought after by livestock for the minerals contained in their leaves. Examples include beneficial levels of zinc and boron found in willow leaves as well as calcium levels approximately 1.5-2-fold higher in alder, willows and oaks than in grass, which could be especially beneficial to lactating ruminants.152
The best and most cost-efficient method to achieve this level of plant diversity is to mimic natural grazing patterns. Bison didn’t run a single piece of equipment in their centuries of managing the North American landscape, so why should we think we need to rely on replanting? That’s not to say that replanting can’t be beneficial in some instances, but think about it: how did such diversity show up without anyone intentionally planting a single seed? The answer is that roaming herds of animals were constantly on the move, both to find better quality food and to avoid becoming sitting ducks for the predators moving along their flanks. This led to intense grazing events of tight herds over a short period of time. This style of grazing on the move prevented animals from eating plants down to the soil surface and it allowed for uniform distributions of manure and urine, as well as uniform trampling of plant material onto the soil surface. And of course, the key to it all is that the herd did not return for a long time, providing an extended recovery and rest period for the plant community. During this time, trampled plant material provided the soil armor to conserve moisture and protect against erosion, while the living roots from recovering plants provided all of the aforementioned benefits that living roots bring to the soil ecosystem. In addition, plants were allowed to complete a whole growth cycle and produce seeds to support future generations of offspring. If wind, rain, birds or other small animals didn’t distribute these seeds, then the large herds would certainly shatter and spread these seeds in their hair coats and manure as they lumbered their way through the landscape. Some of these seeds germinated in the next growing season, but many sat in the soil for years waiting for their moment to shine. Years, decades and centuries of patiently waiting seeds accumulated and created the all-important “latent seed bank” we are attempting to stimulate with AMP grazing.
In Israel, one date palm seed had to wait 2,000 years before agricultural experts successfully germinated it. Amazingly, the tree has now produced dates of its own, proving that seeds are designed to last!153 The tough outer coating allows them to endure the elements, and its internal nutrient reserves last the embryo for years while its receptors decide whether or not the conditions are right to germinate. Conditions that determine whether a seed stays dormant or germinates include water content, light condition, ambient temperature and nitrogen availability.154 All of these factors are positively influenced by AMP grazing. In the soil, AMP grazing leads to better structure, fertility, microbial activity and water retention. Aboveground, plant material is trampled uniformly and the soil armor protects against soil erosion, water evaporation and wild temperature swings. Consistency in moisture and temperature are especially critical for the reappearance of perennial species. Perennials also recognize that the time is right to germinate when the soil has tremendous fungal activity and a well-aggregated structure. Perennials are desirable because their deep root systems allow them to access water and nutrients lower in the soil profile. In addition, deeper roots increase aggregation lower in the soil profile and enhance deep soil carbon storage.155 These attributes make pastures plastered with perennial plants more resilient to droughts and deluges alike.
The next reason to move toward a diverse pasture is that it extends the growing season dramatically. Given that the majority of grazing costs are incurred with winter feeding, this should capture every grazier’s attention. The trouble with monoculture pastures is that they have a very defined peak growing season with exclusively vegetative forage in the beginning and plants trying to express their reproductive genes toward the end. Outside of that narrow range of activity, there’s not much growth happening. Diverse pastures, on the other hand, offer livestock a variety of plants at various stages of growth throughout the year with some starting their annual growth cycle earlier and others starting later. As a result, one group of ranchers in Western Canada reported that AMP grazing allowed them to start grazing with a mean initiation date of grazing of April 25, as compared with May 17 for non-AMP operations. Notably, four AMP operations reported “year-round” grazing (in Canada!). The total length of grazing was 54% longer (at nearly 7 months) on ranches using AMP grazing, even after the adjustment for dormant season grazing.156 Of course, this is anecdotal but it certainly makes sense given the diversity that AMP grazing is proven to bring.
Lastly, pastures full of diversity provide a better opportunity to run a diversity of livestock. For instance, cattle and bison prefer grass species, sheep prefer forbs and other broadleaves and goats seek out forage from woody species. Mixing livestock species offers a greater greater utilization of pasture and often more efficient conversions of forage into animal protein157, making mixed species grazing “one of the most biologically and economically viable systems available to producers, especially on landscapes that support heterogeneous plant communities.”158 The benefits don’t just stop with domesticated life, either. AMP graziers often witness wildlife returning to their operations that hadn’t been seen in years. This is particularly true of bird populations. Dr. Allen Williams of Understanding Ag observes that, “On farms and ranches that have implemented good adaptive grazing practices, I have witnessed an explosion of bird populations, from ground nesting birds to migratory birds, to songbirds.”159 Research and observation appear to back up Williams’ claims. One study found that Holistic Resource Management (HRM; a system with similar principles to AMP grazing) pastures had “1.5 times higher average abundances of obligate grassland birds than minimally rotated pastures and 4.5 times more obligate grassland birds than continuously grazed pastures.”160 White Oak Pastures, a regenerative operation in Bluffton, Georgia, has also observed a drastic increase in predator bird populations, as evidenced by bald eagle populations increasing from zero in decades past to roughly 78 bald eagles that have made their home at White Oak Pastures in the winter.161 It’s clear that management made all the difference, but how?
As the Louisiana Bobwhite Recovery Plan states, “Habitat is the problem and habitat is the solution.”162 AMP grazing creates the proper habitat by leaving taller stands of plant material and a diversity of heights, which provides cover for birds at different levels, including the ground nesting bobwhite. Grassland bird populations in North America desperately require a rebuilding of their habitat, as the two images below illustrate.
Having a stable source of food is also an important factor in providing habitat. In the case of White Oak Pastures, they believe the introduction of pastured poultry played a key role in attracting bald eagles to their land. Believe it or not, they may have done too good of a job as bald eagles were killing up to four chickens and costing them upwards of $1,000 in daily losses.163 Thankfully, there is another food source that won’t cost a producer thousands of dollars when wildlife eats them by the millions. That food source is the insect population. Many animals rely heavily on insects as a major food source, including various mammals, birds, amphibians, arachnids and insects themselves. Insects are much more than just a food source, though. Some of their invaluable services include manure distribution, degradation of plant litter and, of course, pollination. In other words, ecosystem functioning depends heavily on these six-legged heroes, so we have a real incentive to promote their abundance and diversity. Unfortunately, the news bombards us with pieces about an impending “insect apocalypse” (although that may not be happening in North America, one study claims), so it’s exciting to read how AMP grazing positively affects insects. Research on the subject is showing that AMP grazing, and the increase in plant production and diversity it brings, are benefiting insect populations in a big way:
- High stocking densities, frequent rotational grazing and elimination of prophylactic ivermectin use resulted in greater insect species richness, diversity, predator species abundance, and dung beetle abundance than more conventionally managed rangelands.164
- Although dung beetles only represented 1.5–3% of total arthropod abundance, they were significantly correlated to more abundant and complex total arthropod communities. A diverse community contributes to dung degradation in rangelands, and their early colonization is key to maximizing this ecosystem service.165
- Our study shows that high plant diversity can contribute to a faster transition of insect populations towards naturally occurring community assemblages and at later stages to more stabilized assemblages.166
- Invertebrate biomass, diversity, and abundance in the soil, on the soil surface, and in the vegetation were positively affected by regenerative practices in all three study systems (cornfields of the Upper Midwest, almond orchards of California, and rangeland systems of the Northern Plains).167
One might think that increasing insect populations is a “be careful what you wish for” type of situation, but the fact is that a rising tide raises all boats. Conveniently for us, there are 1,700 beneficial boats for every 1 pest boat. In Dr. Jonathan Lundgren’s words, “For every insect species that is a pest, there are 1,700 species that benefit agriculture or society in some way.”168 Arthropod pests in a grazing environment rarely become a serious economic problem anyway. Most pest issues in these setting can be solved through good pasture management practices, so pesticide application “should not be applied as “preventative insurance” because it is rarely economically or environmentally justifiable.”169 Insect pressure in a cropping system, on the other hand, is a whole other ball of (bees)wax. High disturbance, buffets of monocrops and decreased insect predator populations in cropping environments create a perfect storm for pest insects to thrive and wipe out a crop. In the next section, we’ll discuss the benefits a cropping operation can achieve by applying lessons from succession, including insect pest pressure release
Succession on the Farm
At first glance, cropping and succession appear to mix about as well as oil and water. Yes, perennial agriculture and permaculture are growing movements, but the majority of calories consumed globally are from an annual food source. In fact, more than 40 percent of our daily calories come from just three staple crops: rice, wheat and maize.170 How on earth, then, does succession fit into annual cropping systems when the succession clock is reset with each cycle of plow, plant and harvest? Is it even possible to create something resembling a late succession landscape while producing crops to feed everyone? These are difficult questions to answer, but it doesn’t mean we shouldn’t try to replicate levels of ecosystem functioning and efficiency observed in late succession landscapes in cropping systems. Besides, plant community succession is only one piece of the puzzle. Regenerative farmers are proving that their management practices can dramatically shift soil microbial communities and animals communities toward health, balance and efficiency.
On the insect front, recall from earlier the study that found pests to be 10-fold more abundant in insecticide-treated corn fields than on insecticide-free regenerative farms.34 Regenerative, in this case, was defined as farms that “used mixed multispecies cover crops (ranging from 2–40 plant species), were never-till, used no insecticides, and grazed livestock on their cropland.” The conventional farms in the study “practiced tillage at least annually (36 fields on eight farms), applied insecticides (as GM insect-resistant varieties and neonicotinoid seed treatments), and left their soil bare aside from the cash crop.” Although both groups of farms raised monocrop annual corn, the regenerative system applied management practices that resulted in an ecosystem that more closely resembled conditions found in nature. These include greater insect diversity, enhanced biological network strength and greater community evenness. Herein lies the key to biological insect pest management. It’s the “balance of species within these communities that contributes to pest suppression in maize fields.”171 That’s not to say practices that solely increase predator populations are a waste of time, because they aren’t172, but the point is that it takes a whole community to provide long-term stability. To this end, the authors add that “species diversity of the entire community [not just higher trophic levels173] may contribute to pest suppression within realistic arthropod communities.” Did you catch that? The entire community. This means the total annihilation or extinction of pest insects from a field is undesirable in the first place! A more sustainable goal is to build a functioning ecosystem that has the ability to maintain pest populations at healthy levels, thus maintaining an important food source for many beneficial species that consume these crop pests.
The only way to achieve this level of balance is to provide nature with the time, space and resources it needs to self-regulate and self-organize into the proper balance and evenness found in that specific context. Conventional practices, especially insecticide usage, disturb insect communities too frequently and too violently for them to create a system defined by balance, evenness and resilience. The following is a short list of research documenting disturbances to beneficial insect species from insecticide use. (Note: When reading the following study results, bear in mind that enemies and predators (i.e. lacewings, ground beetles, lady beetles, predatory wasps and spiders) refer to species that are predators of pest insects. They are enemies to the pests, not us!)
- The laboratory trial revealed that all bioactivity of the seed treatments against soybean aphids was gone within 46 days after planting, prior to aphid populations damaging the crop. Bean leaf beetles, a sporadic pest in our area, were reduced by the seed treatments. Natural enemy communities were significantly reduced by thiamethoxam seed treatments relative to the untreated control, particularly populations of Nabis americoferus (Hemiptera: Nabidae). Chrysoperla (Neuroptera: Chrysopidae) adults were reduced in the imidacloprid- treated plots.174
- Seed-treated fields of sunflower had significantly fewer above-ground natural enemies and pollinators than untreated fields, while subterranean predators were unaffected.175
- The commercial formulation of 2,4-D was highly lethal to lady beetle larvae; the LC 90 of this herbicide was 13 % of the label rate. In this case, the ‘‘inactive’’ ingredients were a key driver of the toxicity. Dicamba active ingredient significantly increased lady beetle mortality and reduced their body weight.176
- Rates of parasitized diamondback moth were consistently lower in the treated fields. Negative effects of using insecticides against diamondback moth were found for the density of parasitoids and generalist predatory wasps, and tended to affect spiders negatively.177
The side effects of regenerative practices, on the other hand, are proven to increase beneficial species and functional groups.
- Our research suggests that agronomic practices that promote high levels of arthropod diversity fundamentally require fewer agronomic inputs. For example, reducing tillage178,179, increasing vegetation diversity on farms [for example, lengthening crop rotations, including cover crops in rotations, intercropping, managing field margins180], and developing minimal-till organic agriculture181 should help increase biodiversity.182
- Foliar-dwelling predator populations were substantially higher in the cover crop treatment than in the chemical treatments in all years of study; population declines in the latter treatments were strongly associated with insecticide applications targeting soybean aphids. Foliar predator populations did not rebound within the growing season after insecticides were applied.183
- We conclude that low-intensity cropping systems are most favorable to the abundance and function of beneficial ground-dwelling arthropod communities (insectivores and granivores) during the organic transition process.184
- Research indicates that providing non-crop natural or semi-natural vegetation on at least 20% of a landscape will enhance populations of a variety of beneficials, including predators, parasites, and pollinators.185
Wildflower-sown islands within arable fields and grassy field margins both promote spider diversity.186
- Invertebrate richness and diversity, and earthworm abundance and biomass were significantly greater in regenerative almond orchards compared to conventional almond orchards. Pest populations were similar in the two systems.187
Most importantly for pragmatic producers, pest suppression is observed as a result of increasing insect species and functional group diversity.
- Our results suggest that increasing functional diversity (FD) in predatory invertebrates will help maximize pest control ecosystem services in agricultural ecosystems, with the potential to increase suppression above that of the most effective predator species.”188
- Complementarity among natural enemies enhances pest suppression.189
- In terms of pest management, our results indicate that small-scale plant diversification (via the planting of cover crops or intercrops and reduced weed management) is likely to increase the control of specialist herbivores by generalist predators.190
Another positive side effect of creating a balanced ecosystem is that producers can begin to work with pest insects and benefit from their ability to cull plants that are sick, weak and/or nutritionally imbalanced. This may sound like a negative to the producer and plant community, but it’s actually a necessary element in an ever-improving natural system. Ecological relationships like the one between insects and plants are supposed to be in an “arms race” where each side shifts and changes to outsmart the other. Unfortunately, conventional agriculture ties two cinder blocks to the roots of plants before the race even starts. Not only do insecticides make pests stronger through resistance, modern crop management tends to degrade soil health and ecosystem functioning, which creates a need for crop varieties that can only grow efficiently with heavy chemical input regimes. All the while, insects are free to adapt quickly as we trot out the same species in the same fields year after year. This process of insect culling and improvement is more straightforward in a perennial environment, but there are still lessons that can be applied in annual cropping. First, insects are deterred by crops that are healthy and in nutritional balance. Insect digestive systems are quite simple and only produce enzymes that break down simpler compounds. An easy example is what happens to a tomato fruit that remains on the counter for too long. Swarms of fruit flies only show up once the tomato’s complex compounds decompose into simpler compounds that they can handle. The same is true for crops. Healthy crops in nutritional balance take simple compounds, such as glucose produced during photosynthesis and nitrate from the soil, and use them to make complex compounds, such as carboyhydrates and complete proteins. Unhealthy crops are much less efficient at making this transformation, so free-floating glucose, nitrate ions and others are abundant in their tissues. Just like fruit flies, pest insects in the field detect the presence of these simple compounds and feed on them.191
For those interested in learning more, John Kempf of Advancing Eco Agriculture has created the “Plant Health Pyramid” based on years of experience that describes this process in-depth. Kempf has observed time and again that certain pest species are unable to attack plants that have reached different levels of plant health. For example, level two describes plants that are able to transform absorbed nitrate and ammonium ions into complete protein structures. Healthy plants naturally perform this transformation, which confers them with resistance to soft-bodied, sucking or chewing insects with simpler digestive systems. These include tomato hornworm, European corn borer, corn earworm, wireworm, flea beetles, leaf hoppers, white flies, aphids, spider mites and thrips.192 Adequate levels of molybdenum, magnesium, sulfur and boron appear to be the nutrients most responsible to accomplish this task. In addition, plants at level four are healthy enough to produce secondary metabolites that allow them to be fully resistant to the entire beetle family including Japanese beetles, corn rootworm beetles, squash bugs, Colorado potato beetles, cucumber beetles and marmorated stink bugs.192
Given this information, crop producers would do well to prioritize management practices that increase plant health rather than relying on harsh chemicals to kill away the pests (and beneficial species) as the first line of defense. Not only will the current generation of plants benefit, but so will their offspring. This leads to the second lesson: Insects build genetic strength in plant communities over time because healthy plants are more likely to survive and pass on their genes when pests are allowed to take out the weak. The practical application tied to this lesson is that producers can reap the benefits of natural genetic advancement by saving seed from their cash crops and cover crops. No CRISPR cas9 needed! Genetic improvements may come from a beneficial random mutation that grows in the population year after year. Improvements can also manifest themselves through epigenetic changes. Like all living organisms, plants pass on epigenetic markers to their offspring that were created as a result of the specific experiences and conditions they lived through.193 Seeds that germinate in the same location as their parents with similar soil, insect interactions, climate and microbial communities will be better suited to flourish than if they grow up in a distant location where the conditions don’t match up with the experiences encoded in their genetic makeup. Changes from one generation to the next are often subtle, but the summation of subtle changes over years and decades can lead to significant changes in phenotype and performance. One tradeoff of purchasing seed produced off-farm is that producers are forfeiting these potential positive changes that could have accrued over generations. That’s not to say off-farm seeds are bad or anything, but these are trade-offs to consider. The bottom line is that saving seeds is an empowering practice that allows annual cropping systems to increase strength and health over time by connecting one year to the next. One might call it “annual succession”. A bit paradoxical but it’s kind of catchy if you ask me! (Added bonus to saving seeds: a producer’s seed stock (and thus livelihood) aren’t completely at the mercy of giant multinational agrochemical corporations. That’s gotta count for something, right?)
To determine if seed can be saved legally, producers should:
- Review any agreements signed when purchasing the seed;
- Check the label to determine if the variety is protected by the Plant Variety Protection Act (PVPA), patent law, or is unprotected
- Check with the seed company.194
Speaking of seeds, another reason we want to increase insect populations on the farm is to harness their power as granivores, which means “seed eaters”. In fact, invertebrates as a whole can be such prodigious consumers of weed seed as to appreciably reduce weed seed density and emergence.195,196,197 This is great news considering how difficult weed management can become in annual agriculture. Most weed issues arise from the fact that conventional cropping practices hit the reset button on succession every year and create what I call “weed heaven” (and no, I’m not talking about Colorado). Weed heaven refers to a bare, compacted soil with low biological activity, particularly in regards to soil fungi.198 The root cause of these conditions is management, which can sound overly negative, but it’s also positive because it means the root solution is also management. This should bring producers hope because it means they have agency to make the changes that create a positive difference on their land that leads to less weed burden over time.
Not to sound too hippy-dippy, but the first step to living in harmony with all plant species requires a mental change in perspective. Remember, if you want to make small changes, change the way you do things. If you want to make big changes, change the way you see things.199 To make a truly positive change in weed pressure over time, we first need to adopt the mindset that weeds are our partners in land management, not our enemies. Yes, certain plant species can be aggressive and cause serious economic damage, but that’s because their strengths give them a competitive advantage in those harsh environmental conditions. We need to appreciate the fact that the plants we call weeds are providing crucial services to the ecosystem in an effort to move it along the succession timeline and restore efficient ecosystem functioning. These services include feeding soil biology, breaking up compaction, improving water infiltration and drawing up nutrients from deeper in the soil profile. For that, we should get in the habit of saying “thank you, weeds”, even if the first few times are done through gnashing teeth.
Once we see that weeds play a positive role in ecosystem functioning, it’s time to design a management framework that mimics their strengths in a manner that leads to ecologic and economic gain. Case in point, weeds are excellent at filling in bare soil spots. This is an ecological benefit because bare soil, as Ray Archuleta puts it, is “naked, hungry, thirsty and running a fever.” Therefore, we can mimic the beneficial role of weeds by keeping the soil covered with a combination of residue and growing plants. To maintain residue cover, producers should prioritize a reduction or elimination of the tillage events that break apart residue and bring soil up to the surface. This isn’t a magic solution to weed pressure, and new challenges certainly emerge in reduced-till and no-till management systems. Many producers respond to these challenges by relying on herbicides to prevent weed outbreaks, which is a viable option, but herbicide effectiveness isn’t guaranteed forever, as evidenced by the rising rates of herbicide resistant weeds and a reduction in the number of new herbicide products hitting the market. Fortunately, many producers are seeing a reduction in herbicide use after implementing reduced or no-tillage management. Check out this video produced by USDA NRCS South Dakota to hear from farmers themselves about the positive effects that no-till has had on weed pressure and herbicide use. As they correctly note in the video, no-till also creates less weed pressure down the line because it doesn’t mix weed seeds into the soil profile. Seeds left on the soil surface are more likely to be eaten by granivores and are more exposed to repeated wetting and drying events, which causes them to crack and become non-viable.200 Finally, it’s important to remember that management practices interact with each other, meaning tillage is just one of many factors determining weed pressure.201 The more intentional we become with implementing various regenerative practices, the more the benefits of each will compound on top of one another.
Another way to mimic weed presence is by filling the soil with living plants in the form of cover crops between cash crops to maintain living roots in the soil as many days of the year as possible. The magic of living roots was already discussed earlier in this article, so no dead horses will be beat on that subject. All that will be said here is that living roots are directly responsible for improving soil health and preventing weed heaven by anchoring the soil, reducing compaction, feeding soil biology and improving fungus:bacteria ratios. Above the ground, living plants reduce weed pressure by competing against weeds for access to precious sunlight. Someone once told me that “shade is the best herbicide”, and, while it may not be entirely true, it makes sense because weeds are just photosynthesizing plants like the rest of them! To achieve weed suppression with cover crops through shading, farmers should plant cover crop species that establish quickly and produce large amounts of biomass to achieve a well-established plant canopy.202,203 Allowing cover crops to grow as much as possible before termination is the next important practice because research shows a “strong relationship between the amount of cover crop biomass at termination and the level of weed control provided by the cover crop” moving forward into the subsequent cash crop’s growing season.204 Planting cereal rye prior to soybeans is a simple first step that producers can take to experiment with cover crops. Cereal rye is an increasingly popular option among farmers given its hardy constitution, quick growth and ability to suppress up to 100% of weeds “under ideal conditions”.205 As an added bonus, soybean cyst nematodes are significantly reduced by annual ryegrass and cereal rye cover crops!206 The wins just keep on comin’ when we introduce more life into the system.
Planting diverse cover crop mixes has also been found to suppress weeds, but research out of Penn State found that most of the weed suppressing effects were largely due to the rapidly growing grass species in the mixes.207 Of course, cover crops have the potential to bring many more benefits than just weed suppression, but anyone whose main goal is to suppress weeds should prioritize maximizing biomass with competitive grass species. These grasses can be isolated, as in the case of monoculture cereal rye cover crops, or in a mix that can attempt to achieve multiple objectives at the same time. Strictly speaking about biomass production, there is ongoing debate as to whether multispecies cover crops grow more biomass compared to individual species grown in monocultures. Some studies show they do208,209 , while others show biomass is comparable between the groups.210,211 Cover crop management varies drastically from one operation to the next, so lumping all multispecies cover crops into one group and extrapolating the results is a real challenge and the results should be approached cautiously. Every context is different, including yours. Additionally, time is an important variable that producers need to consider. After a review of available research, which is quite small on the subject, it appears that increased biomass production from diverse mixes is more pronounced the more months and years the plants are allowed to grow.212 This strengthens the argument for diverse plant species in pastures, but it doesn’t present us with a clear-cut better choice when deciding on a cover crop mix to suppress weeds for a few months between cash crops. However, it must be said one more time that there are many other services that cover crops can provide besides weed suppression, such as nutrient retention, organic matter accumulation and erosion control. Producers need to assess which resource concerns they’re trying to address with the cover crop and then determine if multispecies mixes are necessary to address those concerns.
Another management practice that might suppress weeds through diversity and soil cover is intercropping, which is the practice of planting additional species in the same field at the same time as a cash crop. Intercropping is a more advanced management practice and many regenerative consultants advise producers be very careful if this approach is taken. Simply put, more plants growing in a field with a cash crop increases the amount of nutrients and water that the field must be able to provide for every plant to thrive. The unfortunate truth is that many, if not most, crop fields aren’t functioning at levels of efficiency high enough to handle an increased demand without a simultaneous increase in external inputs. That’s not to say intercropping can’t work in some fields and some situations. It just means that producers can potentially have a disaster on their hands from doing something they heard is a “regenerative practice”, and that’s certainly not ideal. With that disclaimer made, one meta-analysis on the topic of weed suppression did find that “intercropping is generally a useful approach for suppressing weeds in annual crop cultivation. In particular, maize intercropped with legume companion plant (CP) showed yield increase, as a result of efficient weed suppression in non-weeded systems.”213 The key term there is non-weeded systems. The effects were less pronounced in systems that included weeding. As it relates to yield, another meta-analysis on the effects of intercropping discovered that, “intercrop yields vary from much lower than sole crops to much higher across different studies.”214 Again, time is a key variable in these types of studies, and it appears that increasing weed suppression, yields, soil organic matter, and year-to-year stability are more likely to be observed with each additional year intercropping is practiced.215 In other words, intercropping is a practice that requires being intentional, not intentional-ish. Be ready to learn from undesired results in the short-term so the appropriate changes can be made moving forward. Intercropping should be considered as a small piece of a long-term plan whose main priority is to increase ecosystem functioning. Whether or not this practice should be introduced and whether it will reduce weed pressure all depends on the context of the farm and the goals of the producer!
Adding diversity for the purpose of decreasing weed pressure doesn’t just involve what’s in the field at one time. Diversity also refers to the full rotation of plants a field will see before the pattern is back to the beginning, if there is a coherent pattern at all! This means the act of extending a rotation of monoculture crops is still a form of adding diversity to an operation. Producers can choose to accomplish this extension with either cash crops or cover crops. Speaking specifically about corn and soybean rotations, USDA scientist Dr. Randy Anderson recommends the addition of a winter grain to take advantage of their cool-season growth cycle. Dr. Anderson calls this “tapping into time.” This simple addition can pay off immensely, both ecologically and economically, especially when applied with other regenerative practices. Case in point, Dr. Anderson’s own research found that the cost of weed management in a no-till, diverse cropping system was “45% lower, due to resistant weeds being present only in the tilled, corn–soybean system.” The suppression of weed resistance was attributed to crop diversity in the no-till system.216 The graph below illustrates the observed decrease in weed seed emergence with the addition of cool-season crops to a corn-soybean rotation. The image was taken from this informative video of Dr. Anderson explaining the results.
Scientists other than Dr. Anderson are also discovering the synergistic effects of multiple regenerative practices on weed management. In a long-term study at Iowa State University’s Marsden research farm, scientists investigated how cropping system diversification and crop-livestock integration affect productivity, profitability, and environmental quality. Since 2001, three systems have been compared within the experiment: a 2-year corn/soybean rotation, a 3-year corn/soybean/oat + red clover rotation, and a 4-year corn/soybean/oat + alfalfa/alfalfa rotation. The 2-year rotation is managed with conventional rates of mineral fertilizers and herbicides, while lower rates have been applied to the 3-year and 4-year systems, along with periodic cattle manure applications. During the 10-year period between 2006-2016, researchers calculated that “mineral N fertilizer use was 86% and 91% lower, and herbicide use was 96% and 97% lower in the 3-year and 4-year systems, respectively, than in the 2-year system.” 217 That’s great, but not using products is the easy part. The hard part is producing respectable yield and profitability with those lower inputs. So, how did the results stack up in these arenas? Across all years of the study, corn has averaged 4% higher yield and soybean has averaged 16% higher yield in the more diverse systems compared with the 2-year system. In addition, profitability “tended to rise as rotation length increased.” A similar study done by Dr. Anderson generated similar results. He found that corn can yield 24% more when grown only once every 4 years compared a 2-year corn and soybean rotation.218 Interestingly, the corn plantings were part of a 9-year rotation consisting of perennial forages and annual crops, which was found to significantly disrupt weed population growth, reduce weed density and increase soil health metrics in an organically managed system.219
For those still worried about cover crops robbing yield, it’s important to remember that any practice managed poorly can have negative effects on yield and profitability. It all comes back to management and context. Therefore, it comes as no surprise that some results show positive impacts on yield and others show negative impacts. On the positive side, a meta-analysis of research from 1990-2017, found that “the use of cover crops for early season weed suppression did not affect grain crop yield, but improved yield of vegetable crops.”220 In addition, The Sustainable Agriculture Research and Education (SARE) group came to a similar conclusion after surveying farmers nationwide. They write that, “The regression analysis of yields based on duration of cover cropping clearly showed that corn and soybean yields increased in response to the number of years that cover crops were planted in a field. This is presumably a reflection of improvements in soil health.”221 (Note: self-reported survey results should always be taken with a grain of salt. Over-reporting of benefits and an over-representation of producers that have had positive experiences with cover crops likely introduces bias.) On the negative side is a study out of Stanford using NASA satellites which is often cited as proof-positive that cover crops do indeed reduce yields.222 Various websites and magazine can be found parroting the the results of the study, saying “On average, fields with cover crops saw yield declines of 5.5% for corn and 3.5% for soybeans.” What these outlets fail to mention, whether through willful ignorance or otherwise, is that cover crops were more likely to be planted in the lowest quality soils, so it makes sense that their yields were lower than non-cover cropped fields with high quality soil. As the authors write in the discussion section, “The real test of the effects of cover cropping on yields is whether cover cropped years of the same exact areas have higher yields than non-cover cropped years, controlling for weather. Here, cover crops show modest benefits of 0.65% and 0.35% for maize and soybean.” That’s a much different story than simply saying yields were lower following cover crops, isn’t it?
With that said, regions that receive low rainfall do experience unique challenges when it comes to managing cover crops. As a result, one study in the semi-arid region of the United States discovered around a 10% decrease in subsequent wheat yields following mixes and monocultures of cover crops compared to wheat following a fallow period.223 Producers in these dryer region may consider integrating annual forages into the fallow period, as this practice was found to increase net returns 26 to 240%.224 It’s a tough ask, but semi-arid and arid producers need to focus on the long-term benefits of cover crops and/or forage crops because individual years will likely vary, especially before soil health has seen major improvements. Finally, one study claims that the first global review indicated that cover crops can reduce crop yields by approximately 4% relative to no cover crops.225 Whatever the results say, producers need to keep in mind that most studies last four years or fewer simply due to the nature of research and funding. This is not aligned with the targets of regenerative farmers who are thinking long-term and are making decisions based on five, ten, twenty years projections out into the future. The compounding and cascading effects of regenerating ecosystem function on a piece of land takes time. Sometimes there may be a slight yield hit in the initial transition years, but this certainly doesn’t have to be the case, and many argue it shouldn’t be the case in a well-managed transition plan.
Now, back to extended rotations. Hopefully no one fainted or reached for their pitchfork at the suggestion of a 9-year rotation with 3+ years of perennial forage. For anyone that did, they should know that this practice is successfully utilized in many other locations around the world. For example, it’s common practice in the United Kingdom to add an “herbal ley” into a crop rotation. Herbal leys are essentially a temporary pastured cover crop that usually lasts around 2-4 years before forage is terminated and returned to cropland production. Many farmers in the British Isles still raise livestock and crops on the same operation, so it makes a lot of sense in their context to devise such a system.226 Dr. Dwayne Beck recounts a similar system on his travels to visit farms in Argentina. Many crop farmers used a 14 year rotation with 7 years of pastures followed by 7 years of no-till and a diverse crop rotation. Interestingly, the Argentinian government banned beef exports in 2006, so farmers began to grow short rotations, such as soybean after soybean. The pictures below illustrate the stark difference in soil health between these two management systems.
Most American crop farmers don’t raise livestock and they haven’t for decades, so it’s understandable why pastures are left out of most rotations in the States.227 However, as the sixth Principle of Soil Health states, reintegrating livestock onto cropland has been shown to improve weed suppression and lower herbicide use.228,229 Given the increase in ecosystem benefits that AMP grazing exhibits compared to set-stock or set-rotational grazing, one would expect weed suppression to be more pronounced with AMP grazing compared to other techniques. Future research is needed to parse out the difference in weed suppression from various grazing strategies of cover crops. In any case, grazing livestock appropriately on cropland with an herbal ley-type system or simply an annual cover crop is one of the most powerful tools in the toolbox to increase overall ecosystem functioning to levels that mimic late succession landscapes. Weed management is just the cherry on top.
The take-home message when attempting to reduce weed burden in a cropping system without tillage or chemicals is simple: promote active biology. The more life, the less weed pressure over time. Many weeds are simply opportunists using their skills to take advantage of bare, compacted, unbalanced, unhealthy soil. We’ve got to do our best to implement management systems that cover, aerate, balance and improve soil health over the timescale of decades, not just individual seasons if we want to realize a healthy relationship with weedy species. Financial and time constraints understandably create a roadblock to long-term thinking, and this is especially true with American crop farmers, as more than half of cropland in the U.S. is rented.230 Land leasing disincentivizes many producers from investing in ecosystem-building practices whose fruits may not be seen until many years into the future, a time when another farmer may be farming that ground. Therefore, it’s especially important to emphasize the short-term wins provided to a cropping system by adopting a regenerative system that puts the 6-3-4 into practice to advance ecologic succession. Nowhere is the phrase “short-term” more applicable than in the realm of the really, really, really small. As was discussed earlier in the article, rich and diverse microbial populations similar to those found in a late succession landscape create a disease-suppressive soil, whereas inactive and sterile environments invite pathogens to use their skills and take control of the situation. Let’s return to John Kempf’s Plant Health Pyramid to understand how and why regenerative practices in cropping systems rapidly build resiliency to disease pressure without all the harsh chemicals.
According to the Plant Health Pyramid, the first step in producing an abundantly rich and diverse microbiome is to increase photosynthetic production of glucose AND to ensure that all glucose molecules are processed efficiently. (Note: glucose is a basic building block of carbohydrates. It is a simple carbohydrate. Chains of simple carbohydrates that link together are called complex carbohydrates.) Processing glucose efficiently means that the plant is able to use the glucose for its own energy production and combine glucose molecules into complex carbohydrates. Chains of fused glucose molecules are used by the plant as building material like cellulose, as energy storage or as root exudates. Here is where the soil microbiome comes into play. It turns out that the types of carbohydrate in the exudates greatly affects the microbiological population in the rhizosphere. Root exudates containing mostly complex carbohydrates tend to create a disease suppressive microbiome, while root exudates primarily composed of simple carbohydrates tend to enhance soil-borne fungal diseases. How can this be?
It’s a similar concept as our fruit fly/tomato example. Microbes that cause disease are the ones that can utilize simple foods, reproduce faster than other microbes and monopolize the situation. They take the opportunity and run with it, hence the name opportunistic. The potential for disease, according to Kempf, begins when root exudates are mostly soluble (easily digestible) simple carbohydrates, which creates disease-inducing populations of bacteria. Exudates composed primarily of complex carbohydrates will produce disease-suppressive bacterial populations with enough influence to suppress fungal pathogens.231 One of the reasons for this observed phenomena is that disease-suppressive bacterial populations will tend to have a reducing effect on the area surrounding the root. (Note: Reducing refers to something gaining an electron. Electrons have a negative charge, so gaining them is like gaining a debt, which reduces your bank account!) This is important because the activity of many trace minerals like manganese, copper, iron and zinc depends on the amount of electrons they are bonded to. Think about iron. When iron has one fewer electron bonded to it, it becomes rust, which is not useful for the plant or for the side panel of my Chevy pickup truck. Also, think about the ingredients used in most fungicides and anti-dandruff shampoo. (Dandruff is caused by a fungus believe it or not!) Most fungicides contain active forms of copper, while anti-dandruff shampoos often contain active zinc.
In addition to their direct antimicrobial properties, these trace minerals play a crucial role in overall plant health and immune responses. Their presence is needed to activate the enzymes that make pretty much everything happen. Read about this role as “cofactors” in the Nutrient Cycle for more information. Many of these trace minerals need to be in a reduced state to be absorbed and used by plants, so a bacterial population capable of reducing these minerals is crucial for the deterrence of pathogens and the strengthening of plant health. This is a much different strategy to disease management than simply reaching for the chemicals to kill the bad guys. Rather, building resilience is approaching the situation from a positive position of strength, which is a much better strategy considering the microbes we call pathogens are everywhere. Plants are exposed to them all the time, so the real determinant of disease is whether or not the microbiome and plant are healthy enough to keep the population of pathogens in line. In the case of soil-borne fungal pathogens, healthy plants remain healthy primarily because their management of carbohydrates results in a healthier plant surrounded by a beneficial bacterial community. This creates a disease-suppressive rhizosphere and results in deterrence and resistance of even the most maligned species, such as verticillium, fusarium, rhizoctonia, pythium and phytophthora. According to Kempf, there are five key elements that a plant requires for efficient photosynthesis and glucose utilization. These are magnesium (the central atom of chlorophyll), nitrogen (four atoms of nitrogen surround every magnesium in chlorophyll), iron (necessary to build the chlorophyll molecule), manganese (cofactor for efficient photosynthesis) and phosphorus (necessary in transforming glucose into usable energy). Soil amendments and fertilizers may be required to raise levels of these nutrients in the plant to adequate levels initially. However, inputs should always be strategically applied so the demand for them decreases over time as the ecosystem is able to provide a higher percentage of the nutrients that plants need. What we want to avoid is relying on inputs for nutrients and making the biology “lazy”. That’s not efficient for the ecosystem and it’s not efficient for the wallet.
The second level of the Plant Health Pyramid was briefly discussed earlier as the ability of plants to synthesize complete proteins, which creates resistance against soft-bodied, sucking or chewing insects like aphids and corn earworm. Level three pertains to how plants produce and manage lipids (a.k.a. fat). You read that right. Fats are an important component of plants, just like all living organisms.232 Life on this planet wouldn’t exist without the contribution of fats, largely because cells, organelles and nuclei are surrounded by phospholipid bilayer membranes. Plants also use lipids as the building blocks for many essential hormones and as a place to store excess energy.233 Fat molecules are excellent storehouses of energy, as they contain 9 kilocalories per gram. (Calories are a measurement of energy.) This is over two times the kilocalories that carbohydrates and proteins hold per gram. As it turns out, plants that consume more energy than they require will store that excess energy in the form of fat, just like us. The difference is that plants don’t store the fat in their bellies and hips. Instead, plants will put some of that energy into fat molecules and exude an increasing amount of fat-based lipids into the rhizosphere, which helps build beneficial fungi populations near the root. Plants also use excess fat to produce a glossy, waxy sheen on the leaf surface. This layer of wax on the leaf helps plants become much more heat and drought resilient through water retention. In addition, a thick, waxy layer provides a physical barrier between pathogens and a molecule in the plant cell membrane called pectin that pathogens often attack to gain entry into the leaf.234 As a result of building beneficial fungi populations and a waxy layer, plants at this stage develop resistance to all of the airborne fungal and bacterial pathogens such as powdery mildew, late blight, fire blight, rust, bacterial speck, angular leaf spot and bacterial spot.
Unlike the first two levels of the Plant Health Pyramid that have distinct nutrients we can point to as the cause of improvements, achieving a high level of fat production is less straightforward. The best way to observe higher fat content in plants appears to be through an overall enhancement of biological activity in the rhizosphere. It’s common knowledge to most producers that there are trillions upon trillions of hungry mouths living and consuming material in the soil. For instance, most producers understand that nitrogen can be “tied up” in the bodies of microbes during the degradation of high carbon:nitrogen ratio residue. What’s not understood is the fact that microbes exude compounds back into the soil environment. Some of these compounds are simple nutrients, but others are biologically active compounds that aid plants in a plethora of ways. These biologically active compounds are called “metabolites” because they’re produced as intermediate or end products of microbial metabolism.235 Because many microbes live in relationship with a host, metabolites are like chemical communication signals by which microbes interact with their symbiotic partner. This includes microbes living in contact with plant roots and also the microbes living inside each of us. Many of these metabolites directly benefit the host upon absorption. For example, our intestinal cells are capable of absorbing many health-promoting metabolites that microbes produce, such as acetate, propionate, and butyrate, which positively impact human cardiovascular, immunologic, neurologic, and metabolic health.236,237 Similarly, microbes living in the rhizosphere exude all kinds of health-promoting metabolites, including plant growth-promoting phytohormones such as gibberellins (GAs), auxins, cytokinins (CKs), ethylene, and abscisic acid (ABA).238 All of this chemical cross-talk has developed from natural relationships that span millennia, so the more we can foster these natural conditions, the more we can take advantage of their health-promoting teamwork.
Metabolites can also be simpler organic compounds like amino acids or amino sugars. Organic, in this case, means it is only produced by living
organisms and has carbon-hydrogen bonds, the hallmark bond shared by all living organisms. Inorganic is something like nitrate (NO3–) or ammonium (NH4+) existing without a carbon atom. Here’s the key point: For plants to have enough excess energy to store as fat, they must absorb a majority of their nutrition in the form of organic microbial metabolites. Simply absorbing their nutrition in the form of soluble, inorganic ions from the soil solution isn’t enough. I know, I know… this goes against pretty much everything we’ve ever been taught about plant nutrition. However, the fact is that plants readily absorb organic molecules when they’re available,239,240,241 probably because of its energy efficiency compared to inorganic absorption. One scientific paper describes the process of metabolite absorption as a “metabolic circular economy, a seemingly wasteless system in which rhizosphere members exchange (i.e. consume, reuse, and redesign) metabolites.”242 Producers that rely on inorganic fertilizers to grow crops are missing out on this huge opportunity to save energy. Their plants have to spend hard-earned photosynthetic energy in order to transform something like nitrate (NO3-) into nitrite, which needs to be transformed into ammonium (NH4+) which then needs to be transformed into an amine, which is the “amino” portion of the amino acids that become proteins. Not only does this process take energy, it requires a lot of water. Transforming one nitrate molecule into one amine requires 3 molecules of water, which is why plants stop assimilating nitrate into amines during conditions of low moisture.243
On the other hand, a soil full of biological activity and organic matter will provide plant roots with the ability to forgo this inefficient process and directly uptake organic compounds with pre-made amines. As a result, producers can reduce a plant’s need for water by 30% simply by giving the plant the opportunity to absorb nitrogen in the form of pre-made amino acids and amino sugars. Urea ( H2NCONH2) is also a nitrogen-containing organic molecule that plants can use efficiently, albeit less efficiently than amino acids and amino sugars.244 This is yet another why producers should seriously consider integrating animals back onto their fields. Urine contains urea, which evaporates into ammonia (NH3+) within 48 hours of exposure to the air.245 The smell of ammonia in a housed animal unit is lost nitrogen, lost productivity and lost money! The best way to get productivity from that nitrogen is to have it land directly on the field. Of course, nitrogen isn’t the only nutrient plants need, but it certainly is the most studied. Hopefully future research will be done to elucidate similar patterns of efficiency among the other nutrients.
One area of research that has been done recently is Dr. James White’s pioneering work on the rhizophagy cycle.246 An in-depth description can be found in the article on the Nutrient Cycle, but the gist is that plants are capable of absorbing whole microbes into their roots, not just their metabolites! Whether or not plants receive the majority of their nutrients from this process or just a minuscule amount remains to be seen. What we do know is that absorbing nutrients directly from the cell walls of microbes is a very energy efficient process. It’s also a necessary step if a plant is to reach level four of the Plant Health Pyramid. At this level, the plant is able to produce abundant amounts of plant secondary metabolites (PSM) and hormones. Like lipids, plants always produce secondary metabolites and hormones, but it’s only when they are overly healthy that they can produce them in greater quantities. Traditional teaching is that PSM mediate plant-environment interactions, as opposed to primary metabolites, which are directly required for plant growth. Research done with advanced technology is now discovering that metabolites of all sorts are multifunctional, and the line separating primary from secondary is quite blurred.247 Regardless, scientists do know that PSM like phytoalexins, terpenoids, bioflavonoids, sesquiterpenes and tannins are involved in processes that make plants stronger and healthier. This includes protection against UV radiation, insect attack, disease attack and overgrazing of animals.
PSM and hormones are also critical for stimulating induced systemic resistance (ISR) and systemic acquired resistance (SAR), the equivalent of a plant’s immune system. Plants can stimulate these systems on their own, by herbivore pressure or by beneficial microbes. In an amazing display of collaboration, research shows that “a wide variety of root-associated mutualists, including Pseudomonas, Bacillus, Trichoderma, and mycorrhiza species sensitize the plant immune system for enhanced defense without directly activating costly defenses.”248 Plant roots provide food to the system, so these clever microbes have figured out that plants provide a higher quantity and quality of food if they can help keep them healthy.
The ability to produce complex organic compounds is the superpower of plants. They can’t run away from danger, so their strategy has been to develop the genes that produce an arsenal of chemicals that keeps them safe and healthy. Whether or not these genes express themselves depends on the environment plants are growing in. In other words, producers are ultimately responsible for the quantity of PSM and hormones produced by the plants in their care. It all comes back to managing the land in a system that builds abundant and active biology over the long-term. This is the key to achieving the highest levels of plant health. As an agricultural industry, we should be aiming toward producing this level of health, not just for ourselves, but for society as a whole. Producers, consumers and everyone in between benefits when our crops are healthy and resilient. Producers benefit because their crops are resistant to insect and disease pressure, which allows plants to put more energy into grain and fruit production. In addition, healthier plants produce more roots and exudates, which feeds the soil, builds biology and improves soil health. From the consumer standpoint, food is our primary intake of health-promoting compounds. The same PSM that protect plants also work in our bodies to protect us when we consume them. The benefits to human health from PSM include the reduction of inflammation and oxidative stress249, the enhancement of brain function250 and the reduction of cancer risk251, among many others. It’s quite amazing when you think about it because it means farmers and ranchers are an integral part of a society’s public health care system. It also means there is a direct link between our treatment of the land and our health status as humans. We can pretend this isn’t true, but we’ll never be able to escape this reality, no matter how physically, mentally and spiritually we distance ourselves from the natural world. Dr. Fred Provenza, in his usual brilliance, describes the situation perfectly. He says, “People will have to learn we are members of nature’s communities. What we do to them, we do to ourselves. Only by nurturing them can we nurture ourselves.”252
So, what are the proven techniques that farmers can implement to produce crops with little disease pressure and abundant levels of health and nutrition? Well, the exact techniques differ depending on who you ask and, honestly, that’s how it should be because no two operations are the same. What works best in New York may not be the best practice for someone in Texas. Or Kenya. Or China. Everyone’s context is different. With that said, every farm around the globe (not counting hydroponics or lab grown foodstuffs) would be wise to implement strategies whose compounding and cascading effects lead to an increase in the population and diversity of the mighty soil microbiome. Recall the discussion from earlier discussing how to build a disease-suppressive soil. The short answer then and the short answer now is to follow the 6-3-4 framework, which builds up the soil microbiome to levels approaching late succession landscapes.
A great place to start for new producers is to prioritize soil armor and having living roots in the soil as many days of the year as possible. This includes cover cropping which is known to increase soil microbial abundance, activity, and diversity.253 A second step is to experiment by applying various rates of fertilizer to observe how well the biology in the soil is cycling nutrients. Synthetic fertilizers eliminate the need for plants to recruit microbes who would otherwise have mineralized nutrients, produced beneficial metabolites or been taken up in the rhizophagy cycle.254 This is especially true for mycorrhizal fungi. Plants overfertilized with phosphorus will recruit fungi at lower rates and forgo the capabilities they offer, not least of which is disease suppression.255,256 Producers are advised to slowly wean off of synthetic nutrient management to avoid major crop failures while forcing the soil biology to work again. Adding diversity and extending the rotation are also techniques proven to build the soil microbiome and reduce disease pressure. For example, the incidence and severity of sudden death syndrome (SDS) in soybeans, a key disease caused by a soil-borne fusarium fungus, have been markedly lower in the diverse 3 and 4 year rotations at Iowa State’s Marsden Experiment compared to the 2-year corn/soybean rotation.217 Besides the difference in rotation, organic nutrients in the form of animal manure and lower rates of synthetic fertilizers were applied during the 3 and 4 year rotations, while the 2 year rotation received full rates of synthetic fertilizers. Manure is proven to benefit the soil microbiome when used appropriately, so this practice likely worked in tandem with a diverse rotation to lower SDS incidence and severity.257 Even better than applying manure is to have livestock AMP graze cover crops or vegetative cash crops at the right time258 to achieve maximum soil biological benefits in the shortest amount of time. Grazing cover crops is also a fantastic way for producers to get the most bang out of their buck spent on cover crop seed. If owning livestock is not desired or not an option, find a local producer looking for forage to be grazed. This is a great opportunity for crop producers to also diversify income streams and hedge against low crop prices.
Initial research has been done which indicates that crops produced on farms utilizing multiple regenerative practices for 5-10 years are in fact more nutrient-dense compared to crops from conventional neighbors that are raised with synthetic fertilizer and herbicide applications. Speaking on their results, the authors of the study write that, “Averaged across all nine farm pairings the regenerative farm crops had 34% more vitamin K (10% more to 57% more), 15% more vitamin E (11% less to 70% more), 14% more vitamin B1 (17% less to 2 times more), and 17% more vitamin B2 (17% less to 3 times more).” PSM content was also higher in crops from the regenerative farms, as they had “15% more total carotenoids (6% less to 48% more), 20% more total phenolics (14% less to more than twice as many), and 22% more total phytosterols (25% less to more than 2 times more).”259 Soil from each of the regenerative farms also contained more organic matter compared to their conventional neighbors. These results are preliminary and the the sample size is small, but they’re extremely encouraging. Future studies should be done to replicate and expand upon their findings. There’s no doubt that additional research will only strengthen the position that farming more in sync with nature is the key to sustainable food production, improved public health and a revitalized rural economy. This last point on economics is vital for producers to know because farming is a business, after all. Talk to any farmer and you’ll understand that every one of them wants to treat the environment well and leave the land better than they found it. Unfortunately, the fiscal realities of farming mean that sometimes paying bills takes precedence over environmentally friendly practices. Like they say, it’s hard to be green when you’re in the red year after year. The good news is that regenerative farming is not synonymous with lower profits. Not even close. Research is accumulating that documents a rise in net profitability for many producers when they introduce regenerative practices into their operation. Of course, nothing is guaranteed and every context is different, but initial findings are encouraging for producers looking to make the transition profitably:
- Management practices hypothesized to enhance yield and environmental performance were adopted by 20.9 million farmers in China in 452 counties from 2005-2015. The increased grain output and decreased nitrogen fertilizer use were equivalent to US$12.2 billion.260
- Regenerative fields had 29% lower grain production but 78% higher profits over traditional corn production systems. Profit was positively correlated with the particulate organic matter of the soil, not yield.34
- The relative profitability in the two systems was driven by the high seed and fertilizer costs that conventional farms incurred (32% of the gross income went into these inputs on conventional fields, versus only 12% in regenerative fields), and the higher revenue generated from grain and other products produced (e.g., meat production) on the regenerative corn fields. The high seed costs on conventional farms are largely attributable to premiums paid by farmers for prophylactic insecticide traits (no insecticide was applied as spray on these fields), whose value is questionable due to pest resistance and persistent low abundance for some targeted pests in the Northern Plains.261,262
- Consequently, net returns to land and management did not differ among systems in the Iowa State Marsden Experiment (p=0.56, mean=$845 per hectare per year, $342 per acre year), though profitability tended to rise as rotation length increased.217
- Long-term field experiments in South Africa demonstrate that, with crop rotation, better yields enable two-thirds of the present total wheat production to be grown with only half the cropped area under the main crop, and with better gross margins—dramatically better with integrated cropping and livestock.263
- Profit was twice as high in the regenerative almond orchards relative to their conventional counterparts.264
The focus of this section on succession in crop production pertained mostly to annual farming because that’s how the world produces the majority of it’s food and also because the majority of the cropping industry still operates on a conventional model. Therefore annual agriculture is one of, if not the, biggest spaces for regenerative agriculture to make a positive impact on the world. Yes, the plant species growing in the field may remain annuals, so succession doesn’t necessarily advance in that way, but producers still have the power to positively advance factors like soil biology, soil aggregation, weed suppression, disease suppression, water cycling and nutrient cycling. To do this, producers should start thinking about ways to add elements into the cropping system that link this year to one, five, ten, twenty years in the future. A good example is seed saving. This practice creates positive epigenetic changes in crops that allows them to become increasingly adapted to a farm’s individual soil type, precipitation patterns, microbiome, annual temperatures and annual daylight schedules. As best as their finances and lease agreements allow, producers should also consider the possibility of adding some element of perennial plants in the landscape. Can a perennial grass or pollinator strips be added? What about trees or hedges? Who knows, maybe in a few years producers will have perennial crop varieties to choose from, like the intermediate wheatgrass variety Kernza® being developed at the Land Institute in Kansas.265 These are all important practices for producers to consider as they navigate a rapidly changing industry tasked with growing more crops profitably on less land with fewer inputs. Regenerative cropping takes effort, thought, time and trial-and-error, but it just might be the best, and only, long-term solution to these Herculean challenges.
Summary
The discussion on community dynamics and succession began with a lesson in physics provided by Sir Isaac Newton, and it will come to a close with a physics lesson from MIT professor Max Tegmark. The following excerpt is taken from his book Life 3.0. He writes, “A simple light ray similarly bends when it enters water (compared to a lifeguard running on the beach first and then diving in the water because they can run faster than swim), also minimizing the travel time to its destination! This is known in physics as Fermat’s principle, articulated in 1662, and it provides an alternative way of predicting the behavior of light rays. Remarkably, physicists have since discovered that all laws of classical physics can be mathematically reformulated in an analogous way: out of all ways that nature could choose to do something, it prefers the optimal way, which typically boils down to minimizing or maximizing some quantity. There are two mathematically equivalent ways of describing each physical law: either as the past causing the future, or as nature optimizing something. Although the second way usually isn’t taught in introductory physics courses because the math is tougher, I feel that it’s more elegant and profound. If a person is trying to optimize something (for example, their score in a game, their wealth or their happiness) we’ll naturally describe their pursuit of it as goal-oriented. So if nature itself is trying to optimize something, then no wonder that goal-oriented behavior can emerge: it was hardwired from the start, in the very laws of physics.”266
Community dynamics and succession simply describe the process by which natural landscapes self-organize and self-regulate into increasingly efficient systems. That’s the goal of an ecosystem, and that’s what it’s collective members are always working towards. The road to efficiency isn’t a straight line, as disturbances like climate change, glaciers and invasive species show. That’s the messy, beautiful, quirky fact of life, but natural landscapes are resilient. They rebound from disturbances by riding the omnipresent flow toward efficiency, oftentimes becoming stronger than they were before. The choice to work with or against this natural flow is up to each of us. Those that choose to work against it incentivize quick reproducing, opportunistic organisms whose job it is to right the ship after disturbances set the ecosystem back. Namely, these are the weeds, pest insects and pathogenic microbes we spend so much time and energy trying to eradicate. And you know what? Who could blame us, given the destruction and plagues they’ve caused over the centuries. However, we can choose to partner with them on their quest for efficiency and take advantage of their impressive strengths. Farmers and ranchers who choose this path incentivize a flow toward diversity, balance and health that ripples outward, affecting every member of the ecosystem, including us.
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