Yield and Nutrient Retention Tradeoffs Associated with Manure Injection on Perennial Hayland.

Manure injection has been widely promoted as an alternative to conventional surface application due to improved manure nitrogen conservation and lesser potential for manure phosphorus loss in runoff. In the US, there has been an emphasis on injection technologies best suited to row crop production. We evaluated trade-offs associated with manure injection on perennial hayland, testing a shallow disk injection implement developed for grasslands in the Netherlands. Liquid dairy manure was either broadcast or injected and a mineral fertilizer control was applied to established orchardgrass plots at spring green up, after the first cutting in late-May and after the third cutting in mid-August. Annual forage yields in 2015 were 20% greater with manure injection compared to broadcast application and similar to the mineral fertilizer treatment. Manure injection reduced ammonia losses but increased nitrous oxide emissions. Runoff data are being analyzed and will be presented. As with many nutrient management strategies, tradeoffs in nutrient loss through different pathways must be considered when evaluating the efficacy of pasture manure injection technologies.