Abstract

Nitrogen is the most important nutrient in pasture production and the use of fertilizer rates should optimize biomass yield of high nutritional value with low cost and minimum impact to the environment. A study was performed with reed canarygrass (Phalaris arundinacea L.) harvested every 70 days in a commercial dairy farm located in the district of Santa Rosa of Oreamuno, in the province of Cartago from November 2010 to January 2012. Three nitrogen doses were applied (100, 200 and 300 kg.ha^-1), and biomass production response and nutritional value through a completely randomized block design was evaluated. Dry matter production was not statistically different (p≥0.05) between the lowest and highest doses (2956 and 3347 kg.ha^-1, respectively), while it showed lower and higher values (p≤0.0001) for samplings between February and April (1632 and 4323 kg.ha^-1, respectively). Ranges in crude protein concentration (14.62 to 19.20%), neutral detergent fiber (54.50 to 70.70%) and net energy of lactation (1.14 to 1.32 Mcal.kg^-1 MS) were the result of significant changes (p≤0.0001) that occurred throughout the year in the reed canarygrass. Strategies to adjust stocking rate and supplementation of dairy cattle should be taken into account in order to fulfilled seasonal limitations encountered in biomass and nutritional value of reed canarygrass during the year.

Keywords: Biomass; phenology; nitrogen fertilizantion; Phalaris