The influence of nitrogen and defoliation on the nitrogen content of Lolium multiflorum cv. Midmar

The response of the nitrogen content in ryegrass (Lolium multiflorum cv. Midmar) to a variation in applied nitrogen (0kg N ha-1, 150kg N ha-1, 300kg N ha-1 and 450kg N ha-1) and defoliation intervals (every 2, 4, 6 and 8 weeks, as well as twice a season) was determined. In a field trial, the four nitrogen levels were combined with the five defoliation intervals. The quality of the dry matter (DM) was determined by Near Infrared Spectroscopy (NIRS). Total nitrogen, non-protein nitrogen and true protein were significantly (P≤0.01) influenced by nitrogen level, defoliation interval and the interaction between these two factors. The total nitrogen content varied from 0.68% to 3.38%, the true protein from 0.57% to 2.74% and the non-protein nitrogen from 0.11% to 0.65%. Nitrogen assimilated in the aboveground material ranged from 9.8kg N ha-1 to 423.0kg N ha-1. Linear relationships (P≤0.01) between total nitrogen, true protein and non-protein nitrogen (NPN) respectively were found. African Journal of Range & Forage Science 2002, 19(3): 167-173