Effects of low rates of nitrogen and phosphorus fertilisers on productivity of an annual African clover, Trifolium quartinianum cultivar Mealton 5, for zero grazing in Kenyan highland smallholdings
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Zero grazing is the cornerstone of dairying in intensively cultivated smallholdings in Kenya. The cut and carry method of forage harvesting increasingly is leading to soil mining, especially of phosphorus (P) and nitrogen (N). This problem is more serious in the Central highlands where the prevalent soil type, nitisol, is inherently low in P and N. A study was carried out at the University of Nairobi, Kabete from October 1999 until July 2000 to determine the effects of low rates of N and P fertilisers on productivity of an African annual clover, Trifolium quartinianum cv. Mealton 5, for zero grazing in Kenyan highland smallholdings. Fertiliser applications were: no fertiliser (P0N0); 27 kg N ha−1 as urea (P0N1); 30 kg P ha−1 as triple superphosphate (TSP) (P1N0); and 27 kg N ha−1 as urea and 30 kg P ha−1 as TSP (P1N1). Plant field establishment was enhanced more by application of both P and N than application of each fertiliser alone. Plant canopy cover and dry matter yield were highest in PINI and PIN0 treatments. Nodule number per plant was significantly (p ≤ 0.05) increased by P application. Leaf crude protein was increased similarly by fertiliser application. The results showed that Mealton 5 productivity (both quality and quantity) was enhanced similarly by applying either 30 kg P ha−1 in TSP form or TSP with urea at 30 kg P ha−1 and 27 kg N ha−1.