By John Nelson, Extension Educator in Lancaster County
The majority of cover crops in Nebraska are planted during and after the fall harvest season, so now is a good time to review the benefits and drawbacks of cover crops, and general cover crop management practices.
The benefits of including cover crops in a corn-soybean rotation have been well established in Nebraska and across the Midwest. Cover crops can reduce erosion, increase soil organic matter and water holding capacity, improve nutrient cycling and suppress weeds, among many other things.
The concern about cover crops using valuable soil water in dry conditions is certainly valid. Cover crops can have a negative effect on available soil water and yield of the subsequent crop. However, UNL research in irrigated seed corn production fields in Seward County showed that fall interseeded cover crops can have a beneficial effect on soil water availability for the subsequent cash crop by reducing evaporative losses in abnormally dry conditions. However, the researchers noted that evapotranspiration and soil water storage are very site-specific and heavily influenced by the climatic conditions at each site.
To address the question of yield reductions in cash crops following cover crops, five site-years of on-farm research conducted by the Nebraska On-Farm Research Network (NOFRN) in Lancaster and Seward Counties were summarized on the UNL CropWatch site (cropwatch.unl.edu/2016/impact-cover-crops-corn-and-soybean-yield-nebraska-farm-research). Table 1 shows that planting rye as a cover crop did not statistically affect yield of the subsequent cash crop.
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TABLE 1. EFFECT OF WINTER-HARDY COVER CROP TERMINATED IN SPRING ON SUBSEQUENT CASH CROP YIELD IN NOFRN RESEARCH STUDIES.
• County: Lancaster
Crop: Soybean
Irrigation: Dryland
Year: 2011
Yield (bu/ac) No Cover: 62
Yield (bu/ac) Rye: 59
Yield (bu/ac) Mix: 61
• County: Lancaster
Crop: Corn
Irrigation: Dryland
Year: 2012
Yield (bu/ac) No Cover: 93
Yield (bu/ac) Rye: 86
Yield (bu/ac) Mix: 91
• County: Lancaster
Crop: Soybean
Irrigation: Dryland
Year: 2013
Yield (bu/ac) No Cover: 56
Yield (bu/ac) Rye: 54
Yield (bu/ac) Mix: 56
• County: Lancaster
Crop: Corn
Irrigation: Dryland
Year: 2015
Yield (bu/ac) No Cover: 172
Yield (bu/ac) Rye: 155
Yield (bu/ac) Mix: 158
• County: Seward
Crop: Corn
Irrigation: Pivot
Year: 2014
Yield (bu/ac) No Cover: 248
Yield (bu/ac) Rye: 247
Yield (bu/ac) Mix: —
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This data does offer the possibility that cover crops can be implemented in Southeast Nebraska without severe yield penalties. However, the true benefits of cover crops can take many years to realize, and it does take patience and a willingness to adapt to the challenges of altering our systems with a long-term soil health goal in mind.
The most commonly used cover crop in Nebraska is cereal rye. It is the hardiest of the cereals and can grow quickly and accumulate significant biomass even in suboptimal conditions. However, there are many other types of cover crops and mixes that can be tailored to fit the specific goals of your operation. The Midwest Cover Crops Council has developed a cover crop selector tool that can help growers decide which cover crop species or mixes fit their goals and operations. The tool will provide information at the county level that accounts for local climate and growing conditions. It can be accessed at midwestcovercrops.org/selector-tools.
Cover crops are a great tool to improve soil health and cropping system resiliency, but implementing them on your farm takes careful planning and a willingness to adapt and learn the best strategies to maximize their value. Contact John Nelson at 402-441-7180 or jnelson158@unl.edu.