ChileanJAR

Growth curves and the effect of an annual fertilization with 64 kg of N/ha, at 11 dates, were determined for a mixed pasture. Fertilization dates were: 5 dates from November to January, 5 from March to May and 1 in August. A basic fertilization with P and K was applied to al) treatments. In addition, an unfertilized check was used. This study was carried out during two seasons (1979/80 and 1980/81) at the Quilamapu Experiment Station (Chillán), in an irrigated volcanic soil. Adjusted growth curves described well the seasonal response of white dover, the grasses and the mixture, when analized separately. Response to N was important only when applied on March 15, March 30, August 15, and November 15. Nitrogen efficiency in producing additionai dry matter varied from 6.7 to 8.1 for each-kg of N applied. Economics of its usage is discussed. Dry matter increases, occurring 6 to 8 weeks after N application, were 400 to 500 kg/ha when compared to the P K fertilized check. There was no ncrease in total annual dry matter production, except for the application made on November 15. Nitrogen applied on August 15 was deleterious, since it reduced white dover contribution to the total dry matter production. Regression analysis indicated that the function y = ax^b gives a good description of the high correlation between pasture growth rate and total sunlight radiation and, in a lesser level, temperature.