ChileanJAR

Four rates of N (0, 32,48,64 kg/ha) were applied once a year, in March, August or November, during two growing seasons (1984-1986), on a irrigated white clover/perennial ryegrass sward, grown on a volcanic soil of the Guilamapu Experiment Station (INIA-Chillán, Chile). A randomized-block design, with four replications, and 2 x 6 m plots was used. Dry matter (D.M.) yield and botanical composition were measured. The plots were cut 8 times, in each season. Soil N was monitored during the experimental period and soil available P and K were determined at the end of the experimento There were no effects of the N rates or times of application on the annual total D.M. yield. Clover percentages, of the annual total D.M. yield, decreased significantly, when N was applied and were higher with the November applications than with the March or August applications. With 32, 48, and 64 kg of N/ha, the seasonal responses (6 weeks after) for the August applications were: 26, 29, and 29 kg, in the first season, and 17,20, and 20 kg of D.M. per kg of N applied, in the second season. The available P in the 20-50 cm soil depth, measured at the end of the experimental period, increased significantly when the N rate was increased, and the available K was significantly higher, where no N was applied. The soil N was not affected by the treatments.