Study on the Influence of Topography and Management Practices on Nitrogen Content of Soils Formed in Biotite-Granite Parent Material on the Jos Plateau, Nigeria

The objective of this paper is to analyse the content of nitrogen in soils formed on biotite-granite parent materials and suggest possible management practices that will ensure the availability of the nutrient for sustainable crop production. Nitrogen is a macro nutrient that is essential to crop growth and production. One of the major constraints to sustainable crop production on the Jos Plateau is soil fertility. The availability of nitrogen and other essential plant nutrients in the soil is a key indicator of soil fertility. The content of nitrogen in soils is affected by a number of factors such as drainage, texture and slope steepness. This study was conducted on one of the important parent materials on the Jos Plateau, biotite-granite, taking into account the influence of topography and management practices by farmers. The result showed that the nitrogen content of the soils were quite low. The surface soils had a range of 0.021-0.140% with mean of 0.065%. The slope facets had means of 0.058%, 0.042%, 0.069% and 0.103% respectively for the upper foot slope, middle foot slope, lower foot slope and depression. The higher content of nitrogen in the depression was strongly correlated (r =0.694) with organic matter. The result for the profile pits revealed that soils in the upper foot slope and depression had higher contents at the surface (0.105% and 0.140%) while the middle foot slope had the lowest. The profile pits with and without application of burnt municipal waste had 0.150% and 0.090% respectively at the surface. T-test gave a value of 0.001 for nitrogen 0.01 to 0.001 for other soil properties indicating strong differences in the means for the two treatments. Crop rotation, planting of cover crops and mixed farming were suggested as management practices that could be used to increase nitrogen content of the soils.