Effects of Excess Copper In Dairy Manure Applied to Cool Season Forage Grasses.

Use of CuSO₄ in dairy footbaths for improving foot health is a common practice. Waste material from footbaths is often disposed of in manure storages and applied to fields. Spreading dairy manure with high Cu concentrations may adversely impact crop growth and quality. Research projects were conducted to determine impacts of Cu from dairy manure on growth and quality of forage grasses. In 3 greenhouse experiments 2 cool season forage grasses, orchardgrass (Dactylis glomerata L.) and timothy (Phleum pretense L.), were tested. Treatments were 0, 5.61, and 11.22 kg Cu/ha incorporated in a sandy loam (Study 1) or a silt loam (Study 2) soil. Study 3 evaluated 0, 27.1, 54.3, and 81.4 kg/ha of Cu incorporated in a silt loam soil. Grasses were cut after initial growth to leave 5.1 cm of stubble and re-growth was harvested at approximately 40.6 cm. Study 4 was conducted in plots at Miner Institute (Chazy, NY). Alfalfa (Medicago sativa L.), orchardgrass, timothy, and reed canarygrass (Phalaris arundinacea L.) were established in strip plots by species. After 2 cuttings, sub-plots of each species randomly received 0, 5.61, and 11.22 kg Cu/ha. In all studies shoots were dried at 55°C for 24 h and analyzed for ash, crude protein, neutral detergent fiber, acid detergent fiber, lignin, and mineral concentration. Roots were harvested in greenhouse studies, dried at 55°C for 24 h and analyzed for ash and mineral concentration. Root dry weight for orchardgrass in study 1 significantly decreased at 11.22 kg Cu/ha (P = 0.007). Application of Cu at 11.22 kg/ha to timothy resulted in a significant decrease in shoot weight at 2^nd cutting (P = 0.03) and new shoots from 1^st to 2^nd cutting (P = 0.04). Study 1 indicates that cool season forage grasses may respond differently to high Cu application from dairy manure.