A comparative analysis of phosphorus fertilizer regimes on seed production of Lablab in East and Central Africa

Abstract Lablab purpureus is an important forage legume in smallholder crop-livestock systems of East and Central Africa. Seed yields of L. purpureus are generally low owing to limited phosphorus levels in most soils. Amendment of soil with phosphorus fertilizers is thus critical in enhancing lablab seed production. The objective of this study was to investigate the effect of varying levels of Phosphorus fertilizers on seed yields and the resulting net benefits associated with each level. The paper examines results from three studies conducted in Uganda (treatments: 0, 15, 30, 40, 60, 80 and 100 kgP205 ha-1), Sudan (treatments: 0, 94 and 188 kg SSP/ha) and Burundi (treatments: 0, 20, 40, 60 and 80 kgDAP/ha). Generally, amendment of soil with P enhanced seed yield by 27, 18.4 and 4% in Uganda, Burundi and Sudan respectively. The highest increments in seed yield of 40, 27 and 5.3% were obtained at 30 kgP2O5, 60 kgDAP and 188 kgSSP Uganda, Burundi and Sudan respectively. Results from dominance analysis indicated that treatments 80 and 100 kgha-1 were dominated and their net benefits were lower than that of the control. In Uganda, marginal analysis showed that the marginal rate of return (MRR) from 0 to 15 and 30 kgP2O5 was 500 and 700% respectively, while moving from 15 to 30 kgP2O5 resulted into a MRR of 274%. The study concluded that the rate of 30kg P205ha-1 was the most economically viable rate for seed production in Uganda.