Assessment of the nitrogen and phosphorus needs and use efficiencies for enhanced maize yields in Mbozi district of Tanzania

A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN SOIL SCIENCE AND LAND MANAGEMENT OF SOKOINE UNIVERSITY OF AGRICULTURE. MOROGORO, TANZANIAA study was conducted in Lumbila, Senjele, Mbimba and Ihowa villages of Mbozi district, Tanzania during 2012 – 2013 cropping season to assess the fertility status of the soils and response of maize to N and P as a strategy for enhanced and sustainable maize production. This study was triggered by the low maize yield in Tanzania due to many factors which include declining soil fertility, soil N and P being the major constraints to maize production. The search for the most appropriate rate of N and P fertilizers in relation to maize that would result in optimum yields prompted this research to be conducted. The experiment was laid as Randomized Complete Block Design with three replications. Maize variety used was “UH 615” with fertilizer treatments of Urea (46%N) and TSP (46% P2O5). Based on the soils analytical data, the major soil limitations for increased and sustainable maize production at the study areas include the deficiencies of N, P, Ca, Zn and low in OM. Application of 80 kg N ha-1 + 20 kg P ha-1 and 120kg N ha-1 + 20 kg P ha-1 significantly (P ≤ 0.05) enhanced maize growth and yield more than other treatments, however, the effect was insignificant on harvest index of maize. Application of N at the rates of 40, 80 and 120 kg ha-1 and combining each rate with 20, 40 and 60 kg P ha-1 reduced NUE while increased PUE of maize in all experimental sites. These findings suggest that as NUE decreased the PUE is increased. This could be related to the increase in N and P imbalances in soils as the rates of N applied increased. Results also indicated an inverse relationship between the higher doses of fertilizer application and benefit cost ratio. Application of 80 kg N ha-1 + 20 kg P ha-1 and 120kg N ha-1 + 20 kg P ha-1 produced the highest maize yields equivalent to 4.4 and 4.2 t ha-1 with the gross return of 2,112,000/= TSh and 2,020,800/= Tsh ha-1 with respect to BCR, respectively. This study further confirmed the role of N and P fertilizers in increasing growth and grain yield in maize production. From these results application of 120kg N ha-1 + 20 kg P ha-1 may be recommended for increasing maize yields particularly in the study areas. However, application of 80 N ha-1 + 20 kg P ha-1 can also increase in the yield of maize. This will greatly benefit farmers in Mbozi district where the supply of N fertilizer is low and cases where farmers cannot afford the cost of high fertilizer input. It is also recommended that while there is a wide-scale adoption of blanket fertilizer recommendation there is a need for site-specific nutrient management for balanced fertilization