Sharing the Wealth of Cover Crops: Improved cover crop and soil health knowledge sharing and networking

Integrating cover crops into agricultural systems can be one of the most important drivers of improved soil health and function.  As early as 3,000 years ago, growers were using green manure cover crops to improve soil fertility.  However, the steady increase of inorganic fertilizer use over the past 60 years and development of modern farming techniques have resulted in less diversified cropping systems.  Increasing environmental concerns associated with nutrient losses from agricultural systems, soil erosion, and high production costs coupled with low commodity prices have led many growers to reexamine cover cropping as a method of increasing soil productivity and function.  Noted effects on soil characteristics as a result of cover crops include increased organic matter (Wander et al., 1994), greater water- and nutrient-holding capacity (Weinert et al., 2002), N contribution from legumes (Vaughan and Evanylo, 1998), improved tilth and aggregate stability (Clark, 2008), and reduced erosion (Pimental et al., 1995).

Soil health management strategies, including cover crops, are known to increase hydraulic conductivity and infiltration rates (Franzluebbers, 2002; Nissen and Wander, 2003), decrease bulk density and compaction (Celik et al., 2004; Evanylo et al., 2008; Khaleel et al., 1981), enhance the size and number of water stable aggregates (Kay and Angers, 1999), lower nutrient losses (Drury et al., 2014), and improve crop yields (Munkholm et al., 2013; Schomberg et al., 2011).

Soil organic matter (SOM) content directly influences many biological, chemical, and physical properties that affect productivity.  The greatest contributor to SOM is crop/cover crop residue.  One of the many benefits of higher organic matter content in soils is improved water-holding capacity.  Soil organic matter can hold up to 20 times its weight in water (Stevenson, 1982), significantly increasing the amount of plant-available water, particularly in sandy soils.  Even in high-rainfall regions, moisture is often a limiting factor in crop production, therefore, greater plant-available water, due to higher SOM content, can increase yield by improving the overall water use efficiency (crop yield per unit of water) of the crop. 

The crumbly, friable, well-aerated soil structure associated with good tilth contributes to improved drainage, reduced crusting and ponding, and ease of seedbed preparation.  Crop rotation and use of cover crops improves soil structure by reducing the impact of compaction by increasing aggregate stability, the measure of the resistance of soil aggregates to being broken down when subjected to disruptive forces.  As early as 1967, researchers noted that aggregate stability increased from 67 to 76% when alfalfa was added to a corn-barley-sugarbeet rotation (Schumaker et al., 1967).  More recent results document that aggregate stability is consistently higher under legume (alfalfa or red clover)-corn rotations compared with continuous corn (Raimbault and Vyn, 1991).  Increased aggregate stability also reduces erosion by making the soil less vulnerable to the destructive forces of wind and rain.

Research cited by Peel (1998) found greater than 50% reduction in soil erosion when corn, barley, and hay were rotated compared with soil erosion from land in continuous corn.  The decrease in soil loss when crop rotation and cover crops are employed is due to several factors including dense canopy cover, reduced cultivation, extensive root systems, and the increased amount of residue returned to the soil. 

Improved water quality, and the role of agriculture in maintaining water quality, in the Chesapeake Bay is a long-term concern in Virginia and other Mid-Atlantic states.  In 2010, President Obama issued Executive Order 13508 that outlines strategies for reaching water quality goals in the Chesapeake Bay (Obama, 2009).  In section 202(b) of the Executive Order, agriculture is credited with reaching 50% of its targeted pollution (N, P, and sediment) reduction goal, but broader and more cohesive efforts, including accelerating conservation adoption and new technologies are needed.  Virginia has identified winter cover crops as one of five agricultural best management practices that will enable the state to reach the necessary pollution reductions.  The Commonwealth currently estimates that cover crops are planted on 100,000-120,000 acres annually (Virginia Department of Conservation and Recreation, personal communication).  However the number of acres planted to N scavenging cover crops will need to more than double to meet environmental targets.  A dramatic increase in acreage will require adaptation and innovation of the current cover crop systems so that they offer greater flexibility and greater appeal and can adapt to specific local conditions and needs.

While there are many successful cover crop “champions” and associated programs in Virginia, there is significant opportunity for improving and coordinating programming.  Too often, our current champions operate in silos without coordinating activities.  This is especially true across agencies and regions of the state.  This lack of coordination has many disadvantages, most significantly duplicative projects and the distribution of inconsistent or contradictory information to end-users by different trainers/influencers.  The sum of impacts by individuals working in isolation can be meaningful, but teamwork offers the much greater rewards of coordinated and collective impact. 

Disorder  --> Individual Impact --> Coordinated Impact --> Collective Impact

(Confusion)       (Isolation)                     (Aligned)                   (Synergistic)

The key objective of this project is to develop a core educational and information-sharing network of individuals and organizations who will: 1) Serve as a focused group and network for guiding cover crop educational programming, outreach and additional research and demonstration; and 2) Participate as the core group of cover crop “expert” trainees and mentors over the two years of this project.  We will conduct numerous in-person trainings with this group throughout Virginia showcasing diverse cropping systems.  This focused group of trainers will be the major hosts and leaders of on-farm cover crop field research and demonstration plots, a key component for information exchange with farmers.  The outcome of these efforts will be a networked group of key influencers who have cutting edge and in-depth knowledge and experience with cover crops in various cropping systems and who then serve as local/regional experts, trainers and mentors.  In addition, we will expand the VCE Cover Crop web page and Blog to be the repository for cover crop information and updates in Virginia.