Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/1/2005
Publication Date: 11/1/2005
Citation: Kleinman, P.J.A., Salon, P., Sharpley, A.N., Saporito, L.S. 2005. Effect of cover crops established at time of corn planting on phosphorus runoff from soils before and after dairy manure application. Journal of Soil and Water Conservation. 60(6):311-322. Interpretive Summary: Planting of cover crops to control erosion from northeastern dairy farms is extremely limited due to short growing seasons. A novel cover cropping system was recently developed by USDA's Natural Resource Conservation Service that overcomes traditional cover crop limitations by seeding the cover crop at the same time as corn is planted. This study evaluated the agronomic and environmental benefits of this new system. For some cover crops (red clover and perennial rye grass), corn silage yields under the new cover cropping system were similar to those from conventional methods. The new system significantly reduced erosion and related phosphorus losses in runoff by providing an extensive ground cover, even in the fall shortly after corn harvest. Results of this study highlight the agronomic and water quality benefits of a novel cover cropping system that holds promise for dairy farms in the northeastern U.S.
Technical Abstract: Phosphorus (P) runoff from agricultural soils is a concern due to eutrophication. A novel cover cropping system using post-emergence imidazolinone herbicides to allow for simultaneous seeding of cover crops with silage corn has been developed for dairy farms in the northeastern U.S., where short growing seasons have limited fall seeding of cover crops. Trials were established at two locations in the Cannonsville Reservoir Watershed, New York, part of New York City's drinking water supply system, to assess the effects of this cover cropping system on water quality. Rain simulations (60 mm h-1) were conducted to evaluate the initial 30 min of runoff from small (1 x 2 m) plots before and after surface application of dairy manure (50 or 100 kg total P ha-1). Corn yields from plots interseeded with red clover and, at one site, perennial rye grass were comparable to those from conventional silage corn. Prior to dairy manure application, losses of P in runoff were primarily a function of erosion. Because all cover crops significantly increased ground cover (up to 95%), total P loads in runoff were significantly lower from cover cropped plots (averaging 10 mg plot-1) than from conventionally cropped controls (averaging 39 mg plot-1). Despite concern that leaching of soluble P from the cover crops could enrich dissolved reactive P (DRP) in runoff, DRP losses from cover crops were generally not different from conventionally-cropped controls. Following manure application, runoff P losses increased by over an order of magnitude. Dissolved reactive P became the dominant form of P in runoff, due to contributions of readily soluble P in manure, with DRP averaging 28% of total P before and 78% of total P after manure was applied. In as much as some cover crops may reduce the need for manure nutrients (e.g., leguminous cover crops reduce need for manure N) cover crops may lower manure application rates and related P losses. Results highlight the agronomic and water quality benefits of a novel cover cropping system that holds promise for dairy farms in the northeastern U.S.