Effect of Application of Organic and Mineral Soil Amendments in a Continuous Cropping System for 10 Years on Chemical and Physical Properties of an Alfisol in Northern Guinea Savanna Zone: Experimental Investigation

Demography and heavy dependence on maize as major staple have contributed to intensive maize production in the northern Guinea savanna of Nigeria. Intensive cultivation of land requires continuous application of synthetic fertilizers and organic amendments to maintain soil productivity. This study assessed 10 years of management practices and inputs on soil quality under maize. Sampled soils were assessed by measuring appropriate physical and chemical quality indicators in the 2006 and 2007 rain-fed cropping season. The treatments were made of urea fertilizer, cow dung, Centrosema pascuorum, Vigna unguiculata and applied to make 45 and 90 kg N ha-1. Results showed that cow dung alone or in combination with sole urea fertilizer at the rate of 90 kg N ha-1 increased soil pH, organic carbon and total nitrogen by 2%, 55%, 17% respectively compared to sole urea. Cation exchange capacity significantly increased by 26% with application of cow dung while bulk density was reduced by 18% and total porosity increased by 15%. Further, moisture contents at field capacity and permanent wilting point increased by 50 and 25% respectively over sole urea treatment. To restore or maintain soil fertility for optimal crop yields under comparative long-term soil productivity, adoption of a balanced fertilization that combines urea fertilizer with animal manure is recommended.