Dairy slurry effects on forage quality of orchardgrass, reed canarygrass and alfalfa-grass mixtures

Comparative studies of the effects of rates and frequencies of application of dairy slurry on forage quality have not previously been conducted. The objective of the study was to evaluate the effects of various rates and timings of application of dairy slurry on forage quality of orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinacea L.) and alfalfa (Medicago sativa L.)–orchardgrass and alfalfa–reed canarygrass mixtures managed as a four-cutting management system. A randomized complete block design with treatments in a split plot arrangement with four replicates was used. The main plots consisted of nine fertility rates, seven slurry rate and time of application treatments, one inorganic fertilizer treatment and an unfertilized control. The sub-plots consisted of the two grasses and the two alfalfa-grass mixtures. Slurry was composed from stored solids scraped from the alleyways of a free-stall housing barn with water added to form a slurry having about 8% solids. Manure was pumped from a liquid spreader tank into 10.4 l garden water cans for manual application to the plots. When compared to the control treatment, application of dairy slurry increased crude protein (CP) more in grasses than in alfalfa-grass mixtures. Application of dairy slurry did not generally affect acid detergent fiber (ADF) and neutral detergent fiber (NDF), but fiber contents were affected by the forage species in a four-cutting management system. Alfalfa-grass mixtures had lower fiber contents than grasses from the dairy slurry application. Dairy manure application had comparable or even greater effects on increasing CP contents than inorganic fertilizer in forage species.