Nitrogen volatilized during the grazing of dryland kikuyu pastures

Abstract

Using a micrometeorological mass balance method, a study was undertaken to assess volatilized nitrogen (N) losses during and after the grazing of dryland Pennisetum clandestinum Hochst. (kikuyu) pastures. Specific objectives were to measure the magnitude of volatilized N loss and to establish the pattern of volatilized N loss over time. Nitrogen losses measured over a period of 120 h ranged from 88 to 946 g N ha^‐1 (at a stocking rate of 3 AU ha^‐1), and from 240 to 2 685 g N ha^‐1 (at a stocking rate of 6 AU ha^‐1 stocking rate). In terms of achieving lower losses, the mean difference in N lost as NH₃ was in favour of the lower stocking rate (3 AU ha^‐1), estimated at 1 051 ± 324 g NH₃ ha^‐1 (P≤0.05). A consistent pattern of NH₃ loss was shown to occur during the season, with higher losses being recorded during the day time and lower losses at night.