by Sanne Kure-Jensen
More and more growers are planting cover crops to improve soil moisture, reduce erosion and maximize profits. Cover crops can include grasses, legumes and forbs planted for seasonal cover. Over time, using cover crops improves yields, organic matter and soil water conservation. This change is most noticeable with diverse crop rotation.
Rob Myers, regional director of Extension Programs and Sustainable Agriculture Research & Education (SARE)’s North Central region, explained that in the last four to five years, nearly three times the acreage in his region has been planted in seasonal cover crops to protect and improve soils. This is especially important between growing seasons with corn, soybeans and wheat. The many benefits of using cover crops are:
• Reduce soil erosion while growing and as crop residue; both stages improve water quality
• Reduce soil compaction
• Increase soil nutrient retention and improve water quality
• Increase soil organic matter, water-holding capacity and rain retention. This can be especially important for cash crops grow following cover crops in drought years.
• Provide/add nitrogen (using legume blend)
• Reduce weed, disease and pest pressure with a breaking in crop cycle
• Increase soil microbial activity and health
• Offer habitat for pollinators and beneficial insects
• Provide grazing opportunity in late fall or early spring
• Improve farmers profitability
Cover crops can be planted at different times of the year depending on the producer goals, nutrient improvement and cropping systems. Fall planted cover crops include cereal or winter rye, oats, tillage radishes, annual ryegrass or hairy vetch. Spring planted cover crops may include spring triticale, oats, Austrian peas, dwarf rapeseed and clovers. Summer planted cover crops can include sorghum sudan grass, foxtail millet and buckwheat.
Impacts on Following Crops
Myers reported that 2012 yields following cover crops rose in all surveyed states — over 9 percent for corn and over 11 percent for soybeans, even under drought conditions. Increased organic matter following cover crops is credited with helping retain and utilize sparse moisture. In the states hardest hit by the drought, side by side field comparisons showed 11 percent yield increase for corn and over 14 percent yield increase for soybeans grown after cover crops, according to producers responding to the survey.
Some producers reported increased yields after just one year of cover crop. Repeated cover crop use showed continued improvements in soil fertility, moisture retention and other benefits regardless of whether no-till or minimum tilling was practiced.
Crop stubble or a residue blanket protects soils from erosion and evaporation. Deep roots of cover crops allow following crop roots to go deeper for water and nutrients. Cover crops support microorganisms, which help roots develop more surface area and soil moisture absorption capacity.
Growers may overseed a grass or legume cover crop into an existing corn or soybean crop in time for the cover crop to provide adequate coverage when the cash crop is harvested. For example, radishes may be seeded into corn (normally arial seeded) before the corn is harvested without impacting corn yields.
This allows better establisment of the radish cover crop and provides for a more effective cover crop.
When cash crops and cover crops are planted together or intercropped with no provision for separate harvesting, they cannot be insured as cash crops.
Summer fallow is a common practice that only grows a crop on the same ground every other year to preserve soil moisture. Continuous cropping or re-cropping are RMA terms for growing crops in dry regions on the same ground year after year. In America’s dryland regions, summer fallow crops like wheat and barley are insurable (at different costs) when farmed using summer fallow or continuous cropping practices.
Jeff Schahczenski, agricultural policy and funding research director, National Center for Appropriate Technology (NCAT), recognized the need for resilient systems for long-term sustainability. American farmers rely on the crop insurance program to protect their investment from variable weather and climate and the crop insurance program has recognized and supported the use of cover crops for many years.
Schahczenski described anecdotal yield increases for growers using cover crops. He heard growing excitement for using cover crops in dryland farming as well as traditional irrigated farming conditions.
The next national agricultural census should produce more reliable data on the acres of cover crops in various regions. Cash crop yields may grow with cover crop use. There are expenses with planting and terminating cover crops.
Schahczenski advocated for allowing careful grazing as a termination practice and/or for potential soil health benefits. This added income stream from grazing cover crops would help offset expenses of cover crop seeds and planting.