The 4Rs for cover crops and other advances in cover crop management for environmental quality

Authors: Delgado, Jorge; GANTZER, C - University Of Missouri

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2015
Publication Date: 9/15/2015
Citation: Delgado, J.A., Gantzer, C.J. 2015. The 4Rs for cover crops and other advances in cover crop management for environmental quality. Journal of Soil and Water Conservation. 70(6):142A-145A. doi:10.2489/jswc.70.6.142A.

Interpretive Summary: These recent studies show that cover crops can be used to provide many different ecosystem services. They can be used to reduce erosion, protect soil health, and conserve soil and water quality. They can also be used for climate change adaptation and mitigation. Due to these positive impacts of cover crops, they can be used to maintain and/or improve soil quality and soil health. These papers also show some of the challenges of using cover crops. Although cover crops can potentially contribute to higher yields, on occasion they can also contribute to negative impacts such as reduced yields (Kaspar and Bakker 2015; Thorup-Kristensen et al. 2003; Essah et al. 2012; Clark 2007; Unger and Vigil 1998). Additionally, cover crops can be an issue in the drier western United States, where water balances and water availability is a key issue (Mitchell et al. 2015; Unger and Vigil 1998). Perceptions of cover crop use are key in adoption of cover crops. Farmers are using cover crops and are viably maximizing conservation and sustainability of systems. Although one of the most difficult problems to overcome may be water availability, for a given cropping system management can be used to provide the benefits of cover crops while maintaining and/or increasing yields of the subsequent crop. As papers in this special issue are showing, there are great advantages to using cover crops and they provide tremendous benefits as far as ecosystem services. However, there are also challenges and a need for additional research. In order to avoid potential negative impacts such as reductions in yields we need to use the right cover crop, with the right planting time, with the right harvesting (killing) time, and with the right management practices to maximize the benefits of cover crops (the 4 Rs for cover crops).

Technical Abstract: Cover crops (CC) are universal tools that can be used to improve management practices to draw multiple benefits with increased sustainability across different continents (Dabney et al. 2001; Reeves 1994; Woodruff and Siddoway 1965; Frye et al. 1985; Holderbaum et al. 1990; Bilbro 1991; Langdale et al. 1991; Decker et al. 1994; Thorup-Kristensen et al. 2003; Delgado et al. 2007). They are universal tools that can contribute to reduced erosion while improving soil quality and health in the face of a changing climate (Delgado et al. 2011; Lal et al. 2011). Cover crops can be used as management tools to increase the return of carbon to the soil and increase the potential for carbon sequestration(Sarrantonio 2007; Clark 2007; Lal 2002; Al-Sheikh et. al. 2005, Sainju et al. 2002). They have the potential to provide multiple benefits such as the flexibility to be used as biocontrol tools, potentially reducing the use of agrochemicals and increasing positive impacts to water quality (Dabney et al. 2001). Cover crops are good and flexible nutrient management tools that can be used as green manures to improve nutrient management and add nutrients to a cropping system, especially nitrogen. They can be used to fix atmospheric nitrogen and cycle nitrogen to increase the yield of the crop that follows; this is especially efficient in low input systems of developing countries and can contribute to climate change adaptation (Kambauwa et al. 2015). Cover crops can be used as scavenger crops to recover nitrogen in the soil profile (especially deeper in the soil profile) and to minimize losses of reactive nitrogen to the environment (Delgado 2001, 1998; Delgado et al 2001ab). They can even be used as reclamation tools to mine nitrate from groundwater and contribute to improved underground water quality (Delgado 2001, 1998; Delgado et al 2001ab). Cover crops are flexible tools that can contribute to increased yields and to increased quality of the crop that follows (Delgado et al 2007; Essah et al. 2012). They are climate change mitigation and adaptation tools and can contribute to reduced emissions of greenhouse gases, especially if cover crops with a high carbon to nitrogen ratio are used (Delgado et al. 2011; Lal et al 2011). Cover crops are useful tools in the USA and other countries that can be used to improve nutrient management and protect air, soil and water quality. However, nutrient managers and conservation practitioners need to consider that when using cover crops, decisions about the type of cover crop and management of the cover crop should consider the site-specific rotation, management and climate. There is a need to use the right cover crop, to plant the cover crop at the right time, to harvest and/or kill the cover crop at the right time, and use the right cover crop management practices, to increase the benefits of cover crops.