Overwintering beef animals on kikuyu (Pennisetum clandestinum) its effect on animal performance and soil fertility

A large proportion of the nutrients ingested by grazing animals are returned to the pasture in dung and urine. These by-products of animal digestion contain many ingredients necessary for plant growth, including nitrogen (N), phosphorus (P) and potassium (K). Disadvantages include a tendency for K levels to increase in soils where large quantities of animal waste are applied. A field study was undertaken on kikuyu pastures on the Cedara Research Station in the Midlands of KwaZulu-Natal in order to evaluate the effects of excretal returns on animal performance and soil properties. Two treatments (T1 and T2) involved no overwintering on kikuyu, followed by no N fertilisation during summer (T1) or the application of 250kg of N/ha during the summer (T2). The third treatment comprised overwintering on the kikuyu with no N fertilisation during the subsequent summer (T3). Overall, initial live mass of the trial animals was 221.6 ± 3.1kg and the live mass gain was 67.6 ± 3.1, 96.2 ± 3.1 and 80.7 ± 3.1kg per steer for T1, T2 and T3 respectively. As expected, the K levels in the soils of the dunged pasture increased. Before N fertilisation of kikuyu pastures with a relatively high fertility status is undertaken, overwintering cattle on the pastures should be considered. Fertiliser N should only be applied if the expected increased return in livestock sales is greater than the cost of the N fertilisation. Keywords: increased potassium; dung; excreta African Journal of Range & Forage Science 2001, 18(1): 31-3