The Influence of Fertilization and Cutting on a Tropical Grass-Legume Pasture

Summary

Experiments involving N, P, and K fertilization, and height and frequency of cutting, were carried out on a mixed pasture of giant stargrass (Cynodon plectostachyus) and centro (Centrosema pubescens) at the University of Ibadan during the growing seasons 1951–61. For the first cut after fertilization yield responses of 17 and 24 per cent resulted from applications of 50 and 100 lb N per acre respectively in various experiments but the effect was transient and recovery of fertilizer nitrogen probably did not exceed 30 per cent. Nitrogen fertilization of sown pastures is unlikely to be an economic practice in Nigeria in the forseeable future. Yield responses of 30 per cent resulted from applications of 2½ and 5 cwt superphosphate per acre with a marked residual effect two years after application. Significantly higher concentrations of extractable inorganic soil P at the higher P fertilization rate after 2 years were largely a reflection of the levels of the iron phosphate fraction, but similar trends were evident in the aluminium and calcium phosphate fractions. No differences were found in total, organic, or residual P. The proportion of centro in one 1959 cut for the 0 and 5 cwt rates of superphosphate were 46 and 38 per cent whereas N had no effect, the reverse of the response normally encountered in a temperate mixed pasture. No response to K was obtained. Increased frequency and height of cutting both resulted in decreased yields of dry matter but cutting at 2–4 inches at 8-weekly intervals appears to be the most satisfactory method of managing this pasture for hay production, with yields of approximately 2¼ tons dry matter per acre.