Neem seed cake nitrogen fertilizer equivalencies as assessed by sorghum at Samaru, northern Nigeria

Abstract

Application of organic materials is imperative for soil and crop sustainability of the generally inherent low fertility soils in the northern guinea savanna of Nigeria. Consequently, a field study was set up at the Institute for Agricultural Research (IAR), Zaria during the cropping seasons of 2009 and 2010 to establish the chemical fertilizer equivalent value of neem seed cake (NSC), and also investigate rainfall pattern in relation to evapotranspiration rates in the region as these two weather determinants affect the planting dates. The experiment consisted of sorghum plots to which milled NSC (with % N greater than 3) and urea (inorganic N source) were applied. Factorial combination of four levels of NSC (0, 1, 2 and 4 t ha-1) and four rates of chemical fertilizer package (0, ½, ¼ and full recommended fertilizer rates of 64 kg N, 32 kg P O , 32 kg K O 2 5 2 for sorghum), making a total of sixteen treatments laid in a randomized complete block design and replicated three times. Results obtained for the cumulative above ground biomass yield in the two-year study indicated that a combination of both NSC and inorganic nutrient source gave higher sorghum biomass yield than when each was applied separately. Although, the 1 and 4 tonnes levels of NSC gave grain yields that were higher than when in combination with NPK, none of the NSC-amended plots recorded a grain yield that was equal to or greater than the recommended optimum inorganic fertilizer rate for sorghum in the region. On the average, the nine treatment combinations of NSC and NPK gave fertilizer equivalent values for the nitrogen contained in them ranging from 35.09 to 60.08. It is therefore recommended that NSC be used complementarily with mineral fertilizer as a source of nitrogen in the ratio 1: 0.25