Strip-tillage reduces productivity in organically managed grain and forage cropping systems in the Upper Midwest, USA

Authors: Weyers, Sharon; Archer, David; Forcella, Frank; Gesch, Russell - Russ; Johnson, Jane

Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2017
Publication Date: 2/27/2017
Publication URL: http://handle.nal.usda.gov/10113/5700740
Citation: Weyers, S.L., Archer, D.W., Forcella, F., Gesch, R.W., Johnson, J.M. 2017. Strip-tillage reduces productivity in organically managed grain and forage cropping systems in the Upper Midwest, USA. Renewable Agriculture and Food Systems. doi: 10.1017/S1742170517000084.

Interpretive Summary: Researchers at the North Central Soil Conservation Research Lab in Morris, MN, and Northern Great Plains Research Laboratory in Mandan, ND, undertook an eight-year evaluation of organic cropping systems. The experiment involved comparisons of tillage, rotation and fertility strategies. Crop yields, weed seed densities and potential gross returns were evaluated over time. Overall system performance was best with conventional tillage and a two-year rotation with a winter cover crop due to more effective weed control. The results indicate the need for better weed management strategies if conservation systems using reduced tillage and diverse crop rotations are to be economically viable for organic production in the Upper Midwest. Scientists, land managers, and policy makers will benefit from this research when they need to develop management systems for organic approaches to agriculture.

Technical Abstract: Globally, tillage is decreasing due to recognized benefits of fuel savings and improved soil health in the absence of disturbance. However, a perceived inability to control weeds effectively and economically hinders no-till adoption in organic production systems in the Upper Midwest. A strip-tillage strategy was explored as an intermediate approach to reducing fuel use and soil disturbance and still enable weed control. An eight-year comparison was made between two tillage approaches, one primarily using strip-tillage (ST) the other using a combination of conventional plow, disk and chisel tillage (CT) approaches. Additionally, two rotation schemes were explored under each tillage, a two-year rotation (2y) of corn (Zea mays L.) followed by winter-rye (Secale cereale L.) and soybean (Glycine max (L.) Merr.), and a four-year rotation (4y) of corn, soybean, wheat underseeded with alfalfa (Triticum aestivum L. and Medicago sativa L.), and a second year of alfalfa. Thus, a total of four management strategies were evaluated, CT-2y, CT-4y, ST-2y and ST-4y. Potential gross returns were used to evaluate management combinations on whole system productivity across crops. Evaluating across years, yields of corn, soybean and wheat were greater under CT than ST. Within tillage strategies, corn yields were not different between 2y and 4y rotations, but soybean yields were significantly lower in the 2y versus the 4yr rotation under ST. Alfalfa yields were not different between the two tillage approaches. Weed pressure, indicated by increased density of weed seeds, increased over the first four years, despite the use of additional weed management strategies including in-row cultivation, rotary-hoeing, harrowing, hand-weeding, and mowing. Gross returns were highest in CT-2y indicating that overall productivity was highest in this system. These results indicate that adopting a strip-tillage strategy for fuel savings and soil health benefits negatively affected system productivity because of insufficient weed control.