Environmentally responsible farming methods are not yet widely used and thus suffer from a lack of acceptance by farmers who are not convinced of their benefits. The Rodale Institute, located in Pennsylvania, USA, is hoping to remedy this situation through scientifically designed trials. Active since 1947, the Rodale Institute has been conducting research into responsible farming and the cultivation of healthy, living soils. Their Farming Systems Trial began in 1981 and is ongoing. Rodale’s research focuses on organic farming methods; organic solutions to insects, diseases and weeds; adapting to climate change; and growing nutrient dense foods (1).
Recent research from Rodale is showing promising results for organic no-till farming processes. Pennsylvania farmer, Daniel Brubaker, has been working with Rodale Institute to explore the impacts on crops of the use of organic production methods that exclude cultivation for weed control. This on-farm trial was funded by a USDA NRCS CIG (US Department of Agriculture Natural Resources Conservation Service Conservation Innovation Grant). Mr. Brubaker is working on this project with research scientists from Rodale Institute (2).
Trial Method (2):
Three trial plantings were employed in this study. All three fields were planted with a cover crop during the fall of 2018.
The cover crop used was hairy vetch (Vicia villosa Roth.) which is a winter-hardy legume. This plant is easy to establish and adaptable to a wide range of conditions. An additional benefit of hairy vetch is its ability to extract nitrogen from the air and store it in its roots, supplying nitrogen to the next crop planted in the same field.
In the spring of 2019, the three trial fields were treated as follows. All three methods meet the definition of organic.
FIELD ONE: The vetch was tilled into the soil using a moldboard plow and cultivating disks with multiple cultivations during the growing season.
FIELD TWO: The vetch was mechanically felled to form a thick mulch and corn (to be used for silage) was planted immediately afterwards. The machine used to down the vetch was a roller-crimper, designed by the Rodale Institute and constructed by Daniel Brubaker’s father, John, in the early 2000’s. It effectively snaps the cover crop stems by crimping them without cutting them through. The mulch resulting from the vetch residues lying on the field has the potential to provide season-long weed suppression and prevent the need for soil disturbance to control weeds.
FIELD THREE: The corn silage crop was planted directly into the living vetch cover crop without any crimping of its stems. This method is known as “planting green”. The sheer amount of growing plants in a green-planted field provides effective competition for light and nutrients which discourages weed growth.
Trial Results (2):
Both no-till methods, crimping the cover crop and “planting green”, showed significantly lower presence of weeds (as measured by weight) compared to the plow and disk method.
There was no significant difference in the yield of the corn silage crop among the three fields.
There was no significant difference in the density of the weeds among the three fields.
There was no significant difference in the nutrient content of the leaves of the corn crop among the three fields.
There was, however, a large difference in the nitrate content of the corn stalks at the end of the growing season. The stalks of the plowed and disked crop contained approximately ten times the amount of nitrate as those of the two no-till treated crops. The amount of nitrate in a crop at the end of its growing season is an indicator of the amount of nitrogen available to that crop as it was growing. Corn is a plant that keeps accumulating nitrogen in its stalk even after its nitrogen requirement is met. This suggests that the level of nitrogen available to the growing plants in the tilled field was excessive. This may be because the tilling process incorporates oxygen into the soil along with the plowed-under plant residues. Oxygen speeds up the decomposition of organic matter by soil microbes and results in the liberation and loss of nutrients such as carbon and nitrogen from the soil (2,3).
Trial Conclusions (2,4):
In this study, no-till systems were shown to be effective in controlling weeds and providing adequate nutrients to support the growth of the crop without compromising crop yields.
The plowing and cultivation growing method caused soil degradation by removing nutrients from the soil. Specifically, nitrogen was concentrated in the corn stalks and carbon was released in the form of carbon dioxide due to the increase in the decomposition of organic matter.
No-till growing methods allowed the soil to release nutrients to the crop gradually and only in amounts required by the plants.
Benefits of using cover crops instead of tillage and chemicals to suppress weeds (2,4):
For the farmer;
Because tilling to reduce weeds is unnecessary, the time and energy required to produce the crop is reduced. This reduces costs.
Higher prices can be achieved for crops grown using a no-till method which increases farm profits
For the environment:
Reduced use of energy which reduces greenhouse gas emissions
Reduced loss of nitrogen and carbon to the environment which reduces greenhouse gas emissions
Reduced pollution from nitrogen run-off and improved water quality
Improved soil health and long-term soil resilience
Improved natural habitats
For the consumer:
Cover crops promote healthier soils. Healthy soils produce greater yields of crops that are higher in the nutrients needed for health. These are the same nutrients that strengthen our resistance to the many chronic health conditions that are increasing in prevalence around the globe.
A Deeper Look Into the Soil:
New research into soil is unravelling the startling and fascinating effect that the health of the soil has on human health. In fact, protecting the soil is now recognized as an important international goal. Soil is much more than an inert filtration medium. It is a living ecosystem that determines the healthiness and nutrient content of the plants that grow within it. The most significant function of soil for human beings may be its role in the production of safe and nutritious foods (5).
The organic component of soil is made up of the microscopic organisms that it can support and the substances they produce as well as decomposing plant matter. The more organic matter present in a soil, the healthier it is. The tiny creatures that live in the soil include viruses, bacteria, fungi, protozoa and algae. Together they make up the soil microbiome. There is a symbiotic relationship between these microorganisms and the plants growing among them. The microbes increase soil fertility, water holding capacity and structure. They support healthy plant germination, vigorous growth and increased resistance to disease. They facilitate increased nutrient content of plants (6,7).
Symbiosis between soil and plants is a mutually beneficial relationship. For instance, plants naturally secrete sugars into the soil during photosynthesis and these same sugars nourish the soil microbes, promoting their function in the transformation of minerals present in the soil into forms that can be taken up by plants. This is important because the main source of minerals for humans is the plants that we eat (6,7). Another cooperative biological process is nitrogen fixing. Nitrogen gas accounts for 78% of the air that we breathe. Plants need it to grow but they cannot extract it from the atmosphere and into their tissues on their own. Some of the bacteria present in healthy soils are nitrogen-fixing bacteria. They attach themselves to the roots of legumes and capture the nitrogen from the air, making it available to the plants that they are living on as well as adding nitrogen to the soil for future generations and for other crops. The plants in turn feed some of the carbon that they have drawn out of the atmosphere to the bacteria. The microscopic population of the soil can even facilitate communication between plants, in effect sending warnings regarding threats such as predators or disease. This interaction of plants with soil microorganisms has a huge impact on the quality of the food that results (6,7).
The contribution of microbes to humans goes even further than this. Some soil microorganisms infiltrate plants so that we eat them along with our vegetables. Research is showing that, once inside our intestines, these microbes that originated in the soil can fortify our own human gut microbiome. Studies reveal that simply being in contact with a natural environment and the microbes it contains appears to make people more resistant to health conditions such as allergies and asthma (8,9).
Organic farming supports and enhances healthy soils and their microbial abundance. A recent review of 56 mainly peer-reviewed studies from around the globe found that farms using organic methods had 32% to 84% higher total microbial abundance and activity in their soils than those of conventional farms. Crop rotation, the use of legumes within crop rotations, low or no tilling, and organic inputs are important farming practices for encouraging healthy soils (10).
Soils degraded by over-tilling and overuse of synthetic chemicals lack in soil microbes, disrupting the interdependent relationship between soil microorganisms and plants. The result is lower overall yields. In addition the plants that grow in degraded soil are nutrient-deficient and offer foods low in nutrition to the humans and other beings who eat them (8,9).
Our food has been steadily decreasing in nutritional value over the last 50 years (11). Conventional farming practices have caused contamination and damage to the soil, the medium in which we wish to grow healthy food crops. Inevitably, the content of healthy nutrients in the crops grown in these inferior soils is suppressed.
Many of the chronic health conditions so prevalent today including heart disease, type-2 diabetes, neurocognitive disorders and autoimmune disease are greatly influenced by the condition of the foods that we eat. The way to healthier foods is through nurturing our soils. This can be accomplished by raising the level of organic matter in the soil.
Agricultural soils have already lost significant amounts of organic matter. It is alarming that soil is considered a non-renewable natural resource because its losses through degradation are not recoverable within a human lifespan (12). Now is the time to employ food production methods that rebuild the soil and improve its resilience over the long term. This will have multiple benefits in the fight against greenhouse gas emissions and climate change and, perhaps most importantly, in our quest for the sustainable production of healthy food for healthy people (1).
3 http://www.fao.org/3/a0100e/a0100e07.htm (Food and Agriculture Organization of the United Nations)
7 Nieder, R., Benbi, D.K., Reichl, F.X. Soil Quality and Human Health. In: Soil Components and Human Health. Springer, Dordrecht.2018. https://doi.org/10.1007/978-94-024-1222-2_1
8 Pascal, M., Perez-Gordo, M., Caballero, T., Escribese, M.M. et al. Microbiome and Allergic Diseases. Front. Immunol. 17 July 2018. https://doi.org/10.3389/fimmu.2018.01584
9 Hanski, I., von Hertzen, L., Fyhrquist, N., Koskinen, K. et al. Environmental biodiversity, human microbiota, and allergy are interrelated. PNAS. May 7, 2012; https://doi.org/10.1073/pnas.1205624109
10 Lori, M., Symnaczik, S., Mäder, P., De Deyn, G., Gattinger, A. Organic farming enhances soil microbial abundance and activity—A meta-analysis and meta-regression. Plos One. July 12, 2017; https://doi.org/10.1371/journal.pone.0180442.
11 Davis, D.R. Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence? HortScience. Feb 2009; 44)1): 15-19.