Effects of Fertilizers on Botanical Composition and Productivity of Pasture on the Sandy Soils of the Tanganyika Coast

Abstract

Marked changes in botanical composition and productivity of an indigenous pasture have taken place as a result of a single application of fertilizer. Over a period of three years, invasion and spread of legumes, particularly Dolichos argentis and the grass Panicum maximum, has occurred on fertilized plots. Basal cover increased from 40-45% on control plots to 90% on the better treatments under conditions of gang-mowing with no removal of herbage. Total dry matter yield, percentage legume in the sward and yields of crude protein from grass and particularly legume, were all markedly increased by application of double superphosphate. Muriate of potash gave further increases in yields of dry matter and crude protein above those of superphosphate, particularly with the legume. The nitrogen fertilizer applied three years earlier was still having some effect on dry matter and protein production. However, nitrogen application depressed the percentage legume in the sward and thus reduced the protein production from that source. Phosphorus produced a marked increase in the organic carbon content and consequently the exchange capacity of the topsoil. Treatments receiving potassium had the highest K contents, but those not receiving this element also showed a marked increase in it. This is thought to be due to the mulching effect of the mowing.