ABSTRACTField experiments were conducted in 2010-2011 and 2011-2012 dry seasons at Research Farm of the Institute for Agricultural Research, Samaru and Kadawa to study the productivity of tomato in response to NPK fertilizer and green manure rates. The treatments consisted of two tomato varieties (Roma VF and UC82B), four NPK 15-15-15 fertilizer rates (0, 150, 300 and 450 kg ha-1) and three green manure rates (0, 5 and 10 t ha-1), laid out in a split-plot design with three replications. The combination of variety and NPK fertilizer was assigned to main plot and green manure rate to the subplot. The variety UC82B was superior to Roma VF to all the measured growth parameters such as crop dry matter, leaf area index, crop growth rate and yield attributes such as fruit number per plant, fruit weight per plant; however Roma VF had higher fruit dry matter and fruit acidity content. NPK fertilization at 300 kg ha-1 significantly increased leaf area index, crop growth rate, fruit number per plant, weight per fruit, fruit yield per plant, fruit dry matter and total fresh yield at both locations. However, increasing NPK fertilizer rate beyond 300 kg ha-1 did not increase yield significantly. Application of 150 kg ha-1 NPK increased soil pH, soil N and reduce soil C:N, soil organic carbon at both locations. Green manure application at 10 t ha-1 resulted to significant increase in growth parameters and yield attributes such as fruit weight per plant, fruit dry matter, fresh fruit yield and fruit acidity in both locations. Generally, green manure application increases soil N, soil P, soil K, soil organic matter and reduced pH, C: N in both locations. Agronomic efficiency (AE) for both varieties of tomato was generally highest at the application of 150 kg NPK and at 10 t ha-1 of green manure (GM) at both locations. Decomposition of applied green manure was fast (4.5%) day-1 and the number of days to 50% decomposition was lowest (11 days) at application of 450 kg ha-1NPK fertilizer at both locations. Regression of total fruit yield to NPK fertilizer response was quadratic while green manure showed linear response at all the locations. The tomato varieties responded differently to NPK application in both locations; for Roma VF the optimum rate was 270 kg ha-1 at Samaru and 280 kg ha-1 at Kadawa and UC82B the optimum rate was 260 kg ha-1 at Samaru and 270.2 kg ha-1 at Kadawa respectively. The combination of 150 kg ha-1 of NPK fertilizer and 10 t ha-1 of green manure will save about 50% when compared with 300 kg ha-1 NPK fertilizer rate alone. The highest percent contribution to fruit yield was obtained from fruits weight per plant at Samaru (20.1, 31.9 and 26.0%) and at Kadawa (22.7, 20.5 and 21.6%) in 2010-11, 2011-12 and mean while the highest indirect contribution was obtained from number of fruits via fruits weight per plant in both years and location. Economic analysis of tomato production at both locations indicated that application of 150 kg ha-1 and 10 t ha-1 using UC82B gave the highest gross margin as well as gross margin per naira (â‚Â�) invested of â‚Â� 1.23k and â‚Â�1.41k gain at Samaru and Kadawa respectively. Based on the result obtained from this study, it can be concluded that variety UC82B was superior Roma VF for its higher yield while Roma VF could be selected for its better processing quality suitable for canning because of its high acidic properties. Lablab green manure is critical to soil fertility and improved the physicochemical properties of soil.
