Cover crop adoption has been a little slower in parts of the Great Plains than in other U.S. regions, probably more due to fear of the unknown or conflicts with crop insurance than actual poor outcomes seen by growers.
But in an article published last month in the Journal of Agronomy, researchers who reviewed decades of cover-crop studies in temperature climates found there are plenty of benefits to cover crops, whether you farm in the warm, wind-swept southern Plains or cool prairies of western Canada.
The magnitude of cover-crop benefits can be highly site specific, and there’s a need for more research data on the multi-functionality of covers for different climates and management scenarios, and for short- and long-term economic returns, says the article’s lead author, University of Nebraska Extension soil management specialist Humberto Blanco-Canqui.
You can read the entire article here. But here’s a sample of what they found:
- Runoff loss can decrease by up to 80%, and sediment loss from 40-96% with cover crops.
- Runoff loss can decrease by up to 80%, and sediment loss from 40-96% with covers.
- Wind erosion potential also decreases with cover crops, but studies are few.
- Grazing and haying of covers don’t adversely affect soil and crop production.
- Cover crops serve as ‘insulation’ for soils, reducing maximum soil temperatures by as much as 41 F and increasing minimum soil temperatures by about 34 C. They can also alter freeze-thaw cycles, reducing the depth to which the soil is frozen in winter, contributing to earl soil thawing in spring.
- Water use by cover crops, and the effect on yields, is somewhat of a tradeoff depending on which studies you’re looking at. A study in Akron, Colo., showed spring legume covers planted in fallow reduced soil water by 2.1 inches ahead of wheat planting when they were terminated early, and about 4 inches when terminated late — which reduced wheat yields compared to fallow plots with conventional tillage.
However, they note that studies in Bozeman, Mont., and Garden City, Kan., found crop yields after covers weren’t reduced even with reduced soil water content from cover crops. And residue and root structures left from terminated covers also reduced water evaporation and improve water infiltration.
The issue of terminating cover crops in a timely matter to preserve as much soil moisture as possible is obviously a question of making proper management decisions. And even if growers are still concerned about yield impacts, some farmers have told us they’ve made anywhere from $40 to $300 an acre in profit from grazing cover crops.
I think the message here is that cover crops may require both some learning and compromise to work them into your rotation, but the benefits will be more than worth it in the long run.
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