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Greening Up with Cover Crops for Yield and Sustainability

Posted by David Granatstein | February 24, 2014

I had the good fortune to attend the National Conference on Cover Crops and Soil Health in Omaha, Nebraska recently.  Soil health is in the limelight these days, with a new soil health initiative at the USDA-NRCS, a new Soil Health Partnership from the National Corn Growers Association, another soil health initiative from the Noble Foundation, and several recent meetings on soil health here in the Northwest including a session at the Washington State Horticulture meeting last December and a day-long soil quality workshop in Mt. Vernon. 

Soil health is defined by the NRCS as “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans”, and is intuitively something we need to care for.  Precisely how to monitor soil health or identify needed research, however, can be a bit fuzzy.  What is not fuzzy is the potential for cover crops to significantly improve soil health.  This was abundantly clear at the Omaha meeting.  While most of the examples presented were from the Corn Belt, they were compelling.  Growers saw yields on fields with previous cover crop history produce more, sometimes a lot more, during the drought of 2012, dispelling the notion that cover crops have to compete for precious water.  Field evidence suggests that cover crops contribute to higher yields by improving water infiltration, water holding capacity, and root system development, along with shading or mulching the soil to reduce evaporation. On one farm, water infiltration went from 0.8 inches per hour when the grower bought the farm to 8 inches per hour after two decades of reduced tillage and cover crops.  Growers are reducing inputs for fertility, weed control, and pest management as cover crops start to provide these services. Cover crops can be important in protecting soil from wind and water erosion.  They are being successfully integrated into reduced tillage and organic systems. And when integrated with livestock grazing, they add cash flow to the farm while still providing the other benefits.

Gabe Brown, a nationally known cover crop innovator from central North Dakota, provided some remarkable numbers about his farm since adding cover crops and reduced tillage to his system.  Over two decades, soil organic matter has risen from 1.7% to 5.5%, no synthetic fertilizer has been used since 2008, few to no pesticides are used, corn yields (this used to be wheat-fallow) are 25% above the county average, and his cost per bushel is $1.42, allowing him to be profitable even if prices are historically low.  Other growers reported similar changes, and researchers validated many of these.  Often cover crops are being added after a farm adopts reduced tillage, so all the benefits cannot be ascribed to the cover crops.  But they bring in needed diversity to the system and add dimensions of soil health improvement not often experienced with reduced tillage alone.  And growers are leading the adaptation of cover crops to their myriad of farming systems and growing environments.

One of the interesting evolutions in cover crop technology is the move to multi-species mixes.  These mixes can contain four, six, eight, or even 15 different species.  A suggested guideline for developing mixes is to include a cool season broadleaf, a warm season broadleaf, a cool season grass, and a warm season grass, and have a legume as well to fix nitrogen.  Selection of cover crop cultivars is happening as evidenced by the multitude of options that seed companies were exhibiting at the conference, including several proprietary oilseed radishes that create large roots for combatting compaction and increasing water infiltration.  Growers have started new businesses selling cover crop seeds, and the opportunity to grow cover crop seed is going to greatly expand.  The need for specialized equipment to plant cover crops under the many possible scenarios is another opportunity highlighted at the conference.

In addition to agricultural benefits, cover crops offer important environmental benefits, particularly for water quality.  They can greatly reduce movement of sediment, nitrates, and other chemicals to surface waters.  Already, about 50% of the farmland in the Chesapeake Bay watershed appears to be adopting cover crop use, a huge step towards improving water quality in that body of water.  Another way to “green up” today’s agriculture.

What does all this mean for Washington?  Already potato growers are using mustard cover crops in their rotation on thousands of acres.  Rye and vetch are common winter cover crops in many parts of the state.  Certainly there are opportunities for creative use of cover crops throughout irrigated agriculture, where moisture is not a barrier to use like it is on dryland grain farms.  While we may not be able to extrapolate directly from the experience of Midwest growers, they provide many starting points and exemplify how well growers can come up with solutions when they see a practice that makes sense both for short-term economics and long-term sustainability.  Based on a recent survey by the Conservation Technology Information Center, 63% of growers using cover crops receive no financial assistance to plant them, presumably because they already know they pay their way.  The median cost of seed from this survey was $25 per acre, with a $12 per acre establishment cost, so growers must be experiencing benefits greater than that. But there is still more to learn about the value of cover crops, both financial and intangible, that will help drive more adoption.

Howard Buffet, whose foundation co-sponsored the conference, talked about the need for a “brown revolution” to address soil degradation worldwide.  Steve Groff, a leading cover crop innovator from Pennsylvania, closed the conference by proposing that “cover crops are health care for the soil.”  Soil health is the desired outcome, and cover crops one way to help get there.  So let’s green up the brown fields with cover crops where we can in the Evergreen State and create a more desirable future.


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