Influence of residual profile mineral- N on sorghum response to applied N at Samaru, Nigeria

Abstract

Contribution of residual profile mineral-N to crop response is often neglected when making fertilizer recommendations due to the still widely accepted perception that mineralisation ceases during harmattan in the northern Guinea Savanna of Nigeria. Consequently, this study was to examine the effect of soil mineral-N on sorghum response to N fertilisation with neem seed cake (NSC) and inorganic fertiliser, and to determine if soil mineral-N can be considered as a part of an N fertilizer recommendation program in this region for the complementary use of NSC. The experiment was laid down in a complete randomized design with three replicates. Soil mineral-N varied from 0.010 to 0.024 kg ha-1 at planting and from 0.007 to 0.013 kg ha-1 at side dressing and contributed substantially to the needs of grain sorghum crop. The grain yield due to applied N ranged from 0.0019 to 0.0839kg ha-1 and was inversely corrrelated with the residual soil mineral-N measured to the depth of 0.15m at planting. The ANFE fertilizer recommendation rates were about 90% more efficient as compared to the traditional method of N fertilizer recommendation based on the yield goal. However, more research is needed using a lower depth (0.9 to 0.12m) considering the scavenging nature of sorghum; also several different sites with varying levels of residual mineral-N should be used to develop a stronger relationship between soil mineral-N and ANFE values. The data indicates that the ANFE concept has potential for including soil mineral-N as an integral part of the fertiliser N recommendation system in the region.