Study highlights lasting benefits of organic practices on soil health and crop productivity

Date:01-03-2020

Organic farming practices enhance soil life, resulting in long-term benefits for soil health that ultimately improve crop productivity, a study published in the journal Agricultural Systems finds. The research, published by scientists at Cornell University, underlines the important role soil-dwelling organisms (SDOs) must play in a sustainable agricultural future. “When I think about crop management, nutrient amendments are not going to be the limiting factor [in crop productivity] for farmers in the U.S.,” said study co-author Ashley Jernigan, a Cornell University graduate student in entomology. “Really, we need to be optimizing these biotic processes in our soil and focusing more on biotic measurements,” Ms. Jernigan said.

Scientists began their research at an experimental farm that, since 2005, had been managed under four different organic cropping systems (reduced tillage, low fertility, high fertility, and enhanced weed management). In 2017, the entire site was plowed under and seeded with sorghum in order to understand how these prior practices affected soil health and crop productivity. The metrics measured by researchers include SDO abundance and community structure, crop productivity, and weed abundance.

These metrics are found to be highly dependent on past management practices. For instance, sorghum planted on the enhanced weed management plot, where the soil was frequently plowed, had fewer weeds, but the SDOs present are those better able to handle disturbances, and less likely to significantly enhance soil health. This contrasts with the reduced tillage plot, which contained an abundance SDOs that enhance microbial activity in the soil and facilitate nutrient cycling. Despite the higher level of weed biomass in the reduced tillage plot when compared to the weed management plot, weeds problems were not overwhelming, and crop productivity was higher with reduced tillage. “If weeds are adequately suppressed, reducing tillage in organic cropping systems can regenerate soil health and increase crop production,” said Cornell professor and study co-author Matthew Ryan, PhD.

The results of this study have important implications for the future of agriculture. As Cornell University notes in its coverage of the research, “The study is important because unsustainable farming practices are depleting soils of biological activity and nutrients, leading to widespread concern about farmers’ ability to grow enough food to keep up with global population growth.”

Thus, this research underscores the importance of a frequently overlooked “limiting factor” in crop productivity – soil health. While chemical-intensive agricultural practices focus on delivering the basic building blocks of plant life – the nutrients nitrogen, phosphorus, and potassium (NPK) – and managing weed and pest problems through chemical pesticides, it all but ignores the soil. Soil in chemical-intensive farming is treated as simply a medium for delivering nutrients, rather than an ecological system that must be considered. In such a backwards system, given that chemical use is harming SDOs and other biological life, such an approach is not surprising.

What scientists found is that crop productivity is closely correlated with specific types of SDOs and the stability of the soil, both of which relate to past management practices. Even within organic systems, different management practices can have different long-term impacts on soil health.

Proponents of chemical-intensive farming often denigrate organic systems for their inability to “feed the world,” while ignoring that it is their harmful practices that are directly undermining the long-term ability to do so. And while yields in conventional systems are plateauing, research on organic systems is still in its infancy. There is no doubt among experts that with additional research like the present study, organic can (and must) feed the world.