Cover Crop Selection and Use in Organic No-Till Farming

Cover Crop Selection and Use in Organic No-Till Farming

Summary

Austrian winter pea, hairy vetch, winter rye, and winter triticale were compared as cover crops in an Organic Zero-till (OZ) system in Iowa, Minnesota, North Dakota, and Wisconsin during 2010. Vegetative mulch in excess of 5600 kg/ha was produced by small-grain cover crops prior to mowing and rolling-crimping. Legume cover crops produced less vegetative mulch, except in North Dakota, where hairy vetch produced over 7000 kg/ha. The delay in seeding until cover crops were killed generally prevented successful production of a following in-season corn crop, but soybean was harvested for grain in three of four states.

Objectives/Performance Targets

(1) identify crops and cultivars that are suited as cover crops in organic zero-till systems within the north central region.
(2) refine methods for managing cover crops in certified organic fields that are viable, effective, and do not involve tillage.
(3) determine the impact of organic zero-till farming using cover crops on economics, energy balance, nutrient cycling, pests, and soil quality.
(4) coordinate outreach activities with others involved or interested in organic zero-till farming systems.

Accomplishments/Milestones

Two field experiments were established in 2009. In one, Austrian winter pea, hairy vetch, winter rye, and winter triticale cover crops (CC) were established and maintained along with a no-CC check in plots arranged in a randomized complete block with CC treatments replicated four times at the ISU Neely-Kinyon research farm in Iowa, the UM Southwest Research and Extension Outreach Center in MN, the NDSU Dickinson Research Extension Center in North Dakota, and the UW Arlington Agricultural Research Center in Wisconsin. The four CC treatments were established from August through mid-October, depending on location and treatment. Additional cover crop treatments were included at all locations reflecting local practices and interest. Crop stand was determined after seeding in the fall, 2009, and in spring, 2010, except in North Dakota, where wet conditions delayed seeding most cover crop treatments until mid-October in 2009, thereby delaying establishment of CC stands until following the spring thaw in 2010.

Dry matter (DM), above-ground biomass produced by winter rye (5700 to 10,000 kg/ha, depending on location) and triticale (5900 to 13,000 kg/ha) prior to rolling/crimping or mowing exceeded the 5600 kg/ha minimum threshold considered necessary to suppress weed growth in subsequent, same-season grain and seed crops in Organic Zero-till (OZ) systems. Legume cover crop treatments produced less than 5000 kg DM/ha, except for Austrian winter pea (5600 kg/ha) in Wisconsin and hairy vetch (7000 kg/ha) in North Dakota. Small-grain CC were rolled/crimped (all four locations) and mowed (Minnesota, North Dakota, and Wisconsin locations) at anthesis to kernel early milk growth stages (Zadoks growth stages 60 to 73); Austrian winter pea and hairy vetch were terminated at flowering to early pod set growth stages (BBCH growth stages 59 to 70). Corn was seeded into CC treatments at or shortly after termination treatments were imposed. Armyworm damage forced a second planting of corn into plots in Wisconsin. Corn produced grain after seeding into killed CC mulch only in Minnesota, where yield averaged 6650 kg/ha (106 bu/acre) across all treatments, including the no-CC check (P > 0.05). At other locations, too few heat units remained after killing CC by mowing or rolling-crimping for grain production to be possible. Corn was harvested for silage and yields ranged from less than 1 Mg/ha for some treatments in North Dakota, to almost 60 Mg/ha in Iowa. These first-year data indicate a considerable amount of risk is assumed when seeding corn as an in-season grain crop following small-grain and legume CC in an OZ system in the north central region.

Corn, flax, and bean (soybean in Minnesota and Wisconsin and pinto bean in North Dakota) were seeded into rolled hairy vetch and winter rye CC treatments in a second experiment. Analyses of data collected in this second experiment are not yet completed, although seeding soybean into rolled and crimped hairy vetch can be done successfully in the northern portions of the North Central region.

A second year of field testing will be conducted in 2011 to verify results generated by field tests in 2010. Additional analyses of data (e.g., soil water content) not reported in this preliminary report also will be conducted and reported in 2011.

Impacts and Contributions/Outcomes

Results of this research will determine the potential for growing grain and seed crops in the same growing season that small-grain and legume CC are killed by mowing and rolling-crimping in northern and central states within the north central region and, by extension, in other U.S. states with similar climates, soils, and crops. Strategies for adopting OZ, or Organic Zero-till methods, will be identified. These results will be available immediately upon completion of this project and can be used to guide organic farmers interested in incorporating OZ into their cropping systems within the north central region.

Collaborators: