Organic farmers have long been relying on frequent tillage for weed control, but with newly-developed cover crop-based organic no-till systems, organic farmer Daniel Brubaker is seeing promising results of effective weed control, maintained productivity, and improved soil health.

Demand for organic grains continues to increase in the United States in response to growing consumer demand. Transitioning to organic from conventional chemical farming, however, can be both rewarding and challenging for farmers. Apart from a heightened price premium that would benefit organic farmers, and the healthy food that is essential to human health, organic agriculture will also bring a series of benefits in environmental quality, including reduced pollution from nitrogen run-off and improved water quality; reduced energy use in farming; reduced greenhouse gas emissions; and improved biodiversity and natural habitats, etc. However, because organic farmers don’t spray herbicides to control weeds, frequent cultivation is often required to obtain yields equal to conventional production. Tillage related to physical disturbance, however, has long been considered detrimental to soil health and can increase the risk of erosion. Therefore, excessive use of tillage may offset the benefits of organic farming on soil and environment.

Daniel Brubaker, an organic dairy farmer and agricultural enthusiast in Kutztown, PA, is working with Rodale Institute to explore innovative “organic no-till” management systems. The collaborative trial focuses on growing corn organically, but without the physical disruption to the soil typically used in organic systems in order to control weeds.

Figure 1. (A) Daniel Brubaker (L) and his father John Brubaker (R) use a Roller-crimper and a Monosem planter to terminate hairy vetch cover crop and plant corn. (B) Corn and hairy vetch residues in a rolled and crimped plot.

This innovative system, originally proposed and tested by Rodale Institute in the first decade of the 21st century, is designed to harness the power of winter annual cover crops to achieve effective weed control. Fall-planted cover crops are mechanically terminated in the spring before planting by the roller-crimper (Figure 1). Cover crop residues form a thick mulch that can provide season- long weed suppression.

In this on-farm trial, which is also a part of a project funded by a USDA NRCS Conservation Innovation Grant (CIG), Brubaker is working with research scientists, technicians, and farm staff at Rodale Institute to test the effectiveness of the “cover crop-based organic no-till systems” in terminating cover crops, suppressing weeds, sustaining yields, and improving soil health. Similar experiments are being conducted in Wisconsin and Iowa by farmers and researchers at the University of Wisconsin-Madison and Iowa State University from 2019-2021.

Brubaker planted hairy vetch (Vicia villosa Roth.), a winter hardy leguminous cover crop, in the fall of 2018. In the spring of 2019, he used two different methods, (1) tillage or (2) no-till, to terminate the cover crops and control weeds. The tillage method comprised of using a moldboard plow to kill the hairy vetch, disking and packing to prepare the bed for corn planting, and multiple cultivations in the growing season to control weeds. The two no-till methods were achieved by terminating the hairy vetch using a roller-crimper and planting corn directly into the vetch residues, or planting into the living cover without terminating the cover crops, a method that is referred to as “planting green”.

The roller-crimper was designed by Jeff Moyer, CEO of Rodale Institute and constructed by John Brubaker in the early 2000’s. It has proven to be an effective tool for terminating winter annual cover crops by research trials conducted in different parts of the United States. Its blunt edges snap the cover crop stem without cutting it and its chevron-pattern on the roller allows multiple crimping points and prevents soil disturbance.

The results are spectacular. The roller-crimper (RC) and “planting into living cover” (PLC) treatments showed benefits in weed suppression, with significantly less weed weight compared to the “plow & cultivate” (PC) treatment (Figure 2). There was no difference in weed density, leaf nutrient content, or corn silage yield across these treatments. These results suggest the no-till systems can effectively control weeds, provide adequate amounts of nutrient to support corn growth, and sustain the yield as compared to the common organic tillage systems.

Figure 2. Weed weight, weed density, and leaf tissue nitrogen (N) content of different plots. PC, plow & cultivate; RC, roll & crimp; and PLC, plant into living cover. Different letters above bars indicate significant treatment differences.

However, despite no difference in corn silage yield, the end-of-season corn stalk nitrate was significantly lower in no-till treatments than in the PC treatment (Figure 3). This huge difference might have important implications of soil health and nutrient management. The late season corn stalk nitrate content is a reliable indicator of corn nitrogen status that can provide a good assessment of whether the crop had the right amount of nitrogen, too much nitrogen, or was nitrogen limited. The content in the PC plots (>5000 ppm) was clearly in the range of nitrogen excess, meaning that the corn plants just kept taking up nitrogen from the soil even after their nitrogen requirement had been met. The frequent tillage had possibly stimulated nitrogen mineralization by exposing the once-protected organic matter to soil microbes and introducing oxygen into the soil. Excess nitrogen in the soil could result in nitrogen leaching into ground and surface water.

Figure 3. Corn silage yield and end-of-season corn stalk nitrate of different plots. PC, plow & cultivate; RC, roll & crimp; and PLC, plant into living cover. Different letters above bars indicate significant treatment differences.

Soil organic matter is the foundation of physical, chemical, and biological functions of the soil, and improving soil organic matter is usually associated with benefits in soil fertility, water holding capacity, cation exchange capacity, and better soil structure. Research has shown that 30-50% of soil organic matter has been lost from agricultural soils worldwide, leading to environmental degradation and increased greenhouse gas emissions. Rebuilding soil organic matter in agricultural systems is key to the resilience of food production under climate change.

Results from Brubaker’s field experiments suggest that the soils under organic no-till management could release nutrients slowly and gradually through microbial mineralization of organic matter, to support crop demand. Where frequent tillage is used, excessive nutrients can be released into the environment and subsequently lost through leaching or by accumulation in the corn stalk. In the meantime, a gradual decline in soil organic matter and loss of carbon in the form of carbon dioxide (CO2) can occur. This research data collected by scientists were highlighted at the Soil Science Society of America Conference in San Antonio, TX, in November 2019 and in Rodale Institute webinars. The webinar presented by Dr. Yichao Rui, the Lead Scientist of this project at Rodale Institute, attracted 157 attendees from 12 countries.

This on-farm trial also caught a great deal of attention during Rodale Institute’s Annual Organic Field Day on July 19, 2019. Field day participants were amazed by the Brubakers’ success in managing organic corn production without the use of costly fertilizers and pesticides/herbicides and without frequent in-season cultivation. The robust results provide evidence to farmers of the feasibility of these innovative systems and the potential to improve profitability, reduce nitrogen losses to the environment, and improve long-term soil resilience.