Cover crops are receiving a lot of attention by nearly everyone involved in agriculture. They are once again becoming a very versatile tool that can provide many ecosystem services while also improving a producer’s bottom line.
Cover crops are loosely defined as something planted to serve a multitude of purposes while not typically being harvested as a cash crop. One purpose that is universal to any cover crop is that it can benefit the soil. Since most of the important functions the soil performs (nutrient cycling, as well as water capture and storage, in particular) are biologically driven, cover crops can facilitate an increase in soil health in a big way.
If we examine the four basic principles of improving soil health: less soil disturbance, more plant diversity, living roots in the soil as much as possible, and keeping the soil covered, it becomes apparent how cover crops can help improve the capacity of the soil to function, while providing many other benefits.
The USDA’s Natural Resources Conservation Service defines cover crops as: “… grasses, legumes, and other forbs that are planted for erosion control, improving soil structure, moisture, and nutrient content, increasing beneficial soil biota, suppressing weeds, providing habitat for beneficial predatory insects, facilitating crop pollinators, providing wildlife habitat, and as forage for farm animals. Furthermore, cover crops can provide energy savings both by adding nitrogen to the soil and making more soil nutrients available, thereby reducing the need to apply fertilizer.”
With some forethought and planning, a cover crop can usually serve several purposes at once. For a cover crop to be successful, we need to ask what purposes the cover crop will serve, and how will it fit into your particular agricultural operation?
There are usually one or two primary reasons — and perhaps a few more secondary reasons — that a producer would consider adding a cover crop to their system of production. These reasons will steer the design of the cover crop toward a certain specie of plant or a combination of plants that will fit the desired purposes. This thought process will also shake out the details of when and how the cover crop will be planted and terminated. One must also consider any carryover of herbicides used in a previous crop for weed control, the carbon to nitrogen ratio of the cover crop that remains on the soil, what species of plants in a cover crop would add diversity to the types of plants already included in an existing crop rotation, and any weed, disease, insect, or other pest issues a cover crop might affect in a positive or negative way.
The four basic principles of improving soil health are less soil disturbance, more plant diversity, living roots in the soil as much as possible, and keeping the soil covered.
The primary reasons producers are reexamining cover crops in their operation today seems to be focused on nutrient management, weed suppression, and forage production, with secondary purposes of improving soil health and providing for pollinators. Cover crops can have a tremendous impact on the capture and release of crop nutrients, particularly nitrogen and phosphorous, that could otherwise be lost to surface or groundwater. A soil that is deficient in living plants and soil organisms is a poor sponge for soaking up crop nutrients, when nutrients could instead be held in plant or other organism’s tissues until they eventually break down to be utilized by growing plants again. The best place for plant nutrients to reside is in the cells of plants or soil organisms, not freely moving with water in or across the soil.
With the onset of herbicide resistant weeds, the diversity of plants available for inclusion in a cover crop can provide an excellent opportunity to break the cycle of a specific weed, particularly in a crop rotation composed of only a couple different crops. A cover crop can not only help suppress a given weed by out-competing it, but provide an opportunity to use herbicides with a different mode of action to address the problem weed. By planting a diverse mixture of plants in a cover crop, a producer (or cooperative neighbor) with livestock can harvest some of the cover crop by grazing, providing another opportunity for income and weed suppression at the same time.
At first look, utilizing cover crops might seem a bit complicated, but with some clear goals and proper plant selection, the development and timing of a cover crop can quickly become clear. Cover crops can provide some very significant ecosystem services that can keep the expansion of further environmental regulations at bay while simultaneously making an agricultural operation more efficient and profitable.
Jon Stika is a soil scientist who has worked with the North Dakota Soil Conservation Committee and NDSU’s Dickinson Research and Extension Center. He is also the author of “A Soil Owner’s Manual: How to Restore and Maintain Soil Health.”
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