It’s the right time for cover crops
Nearly 90,000 acres of cover crops were planted in Iowa in the fall of 2012. That estimate is based on data from several sources including sales figures from major cover crop seed companies and cost-shared acres through the USDA Natural Resources Conservation Service’s EQIP program, and the Iowa Department of Ag and Land Stewardship’s state cost-share funding.
Not included in that estimate are many farmers who didn’t take advantage of cost-share funds but added cover crops to their farming systems through saved seed or other outlets.
Cover crops protect soil from wind and water erosion, and capture nitrogen that can otherwise leach from the soil and pollute nearby water sources. According to the state of Iowa’s Nutrient Reduction Strategy Science Assessment, on average cover crops can reduce nitrogen loading by 28% and phosphorus loading by 50%.
Goals to protect Gulf
Meeting the state’s ambitious goal of a 45% reduction in the loss of nitrogen and phosphorus to the Gulf of Mexico seems reasonable when cover crops are added to the equation. However, while immensely beneficial to soil and nutrient protection, winter small-grain cover crops may have a negative impact on corn yields. Commonsense management is vital when adding this conservation practice to a farm.
In 2010, six locations measured an average 12-bushel-per-acre reduction in corn yield following a winter rye cover crop. However in 2009, 2011 and 2012, no reductions in corn yield were measured following a winter rye cover crop.
Soybean yield in 2009, 2011 and 2012 following a winter rye cover crop was the same as if planted following no cover crop. In 2010, soybean yield was 4 bushels per acre greater when following a cover crop.
In 2011 near Clutier in east-central Iowa, farmer Mark Pokorny saw a significant increase in yield of his non-GMO soybeans when they were planted following a cover crop. The cover crop residue controlled weeds in his soybeans, resulting in an 8-bushel-per-acre yield increase.
The possibility of negative effects could discourage farmers from adding a cover crop as a conservation practice to their farms in the fall before a corn crop.
Legume cover crops fix nitrogen and have the potential to decrease a cover crop’s negative impact on corn yield. However, they haven’t been studied or used extensively in Iowa, so little information exists about establishing these nitrogen-producing cover crops.
Legume cover crops in Iowa
Because a large majority of cover crop acres in Iowa are seeded with airplanes or helicopters, finding a legume cover crop that works in this system is important. Members of Practical Farmers of Iowa wanted to learn more.
The PFI farmers participating in cover-crop trials overseeded 20 cover crop species, including pure and mixed grasses and legumes, to determine which species would have the greatest success.
Seeds were broadcast by hand, to mimic overseeding with an airplane. Cover crops were planted when soybeans had their first yellow leaves or corn was nearing black layer.
Plots were 25 feet long and 7.5 feet wide, and two replications of each variety were planted. Ground cover measurements were collected before “winter” snow was predicted at each farm or between mid-November and mid-December.
At Carroll in western Iowa, farmer Art Behrens planted the different cover crops into both standing corn and soybeans, and collected ground cover data on Nov. 17.
As expected, the winter small grains had a greater percentage of ground cover compared to legumes when broadcast-seeded into a standing crop. Still some legume species (winter lentil, common vetch and hairy vetch) also had significant growth under the soybean or corn canopy. Information from this study will help other farmers decide which cover crops may be successful if seeded with an airplane.
Ten farmers around Iowa have completed year four of an on-farm cover crop research project. Cover crop specialist Sarah Carlson cites their answers to the following questions regarding spring management of fall-seeded cover crops.
TIMING: Last spring this rye cover crop had significant early growth at time of herbicide application. “You should kill a winter small-grain cover crop eight to 10 days before planting corn or a couple days before planting soybeans,” says PFI’s Sarah Carlson.
This article published in the March, 2013 edition of WALLACES FARMER.
All rights reserved. Copyright Farm Progress Cos. 2013.