Nitrogen Fertilization and Stocking Rate Affect Stargrass Pasture and Cattle Performance

Abstract

Stargrass (Cynodon nlemfuensis Vanderyst) is an important tropical forage, but the interaction of stocking rate (SR) and N fertilizer rate on stargrass pastures is not well understood. The objective was to determine the effects of three SR (2.5, 5.0, and 7.5 bulls ha−1) and three N rates (112, 224, and 336 kg ha−1 yr−1) on stargrass pasture characteristics and performance of Jamaica Red Poll (Bos taurus × B. indicus) weanling bulls at St. Ann, Jamaica. Soil was a bauxitic clay loam, and pastures were rotationally stocked (7‐d grazing and 21‐d rest period). Pregraze herbage mass increased as SR decreased (2.0‐4.8 Mg ha−1 in Year 1 and 3.3‐8.3 Mg ha−1 in Year 2). Herbage crude protein (CP) and in vitro digestible organic matter (IVDOM) generally increased with increasing SR and N rate. Bull daily gain decreased curvilinearly from 0.70 to 0.26 kg in Year 1 and 0.65 to 0.35 kg in Year 2 as SR increased from 2.5 to 7.5 head ha−1 Daily gain increased linearly as N rate increased from 112 to 336 kg ha−1 The N fertilizer rate had little effect on gain per hectare at the lowest SR, but gain increased with fertilization up to 224 kg N ha−1 for a SR of 5 head ha−1 and up to 336 kg N ha−1 for a SR of 7.5. In conclusion, economic return from N fertilization of stargrass pastures is dependent upon SR, with greater N rates more likely to be profitable if SR is high.