Integrated soil fertility management practices for improved crop production in smallholder farming systems of semi-arid areas: A synthetic review

Abstract Soil fertility degradation is one of the major constraints in smallholder farming environments especially in the semi-arid region of Sub-Saharan Africa. This has been worsened by poor farming methods, lack of technical knowledge and inadequate application of nutrient sources by farmers. The use of mineral fertiliser alone has been cost ineffective and causes land degradation. Although several soil fertility management (SFM) practices have been put forward, knowledge about their benefits, access and adoption by smallholder farmers is still limited. Synthetic review of published articles obtained from Web of Science, Google Scholar and Scopus which cover semi-arid regions across Africa were retrieved and synthesied. Farmers have been applying low organic manure (<5 t ha−1) against the recommended rate of 20–40 t ha−1 depending on soil texture and this caused low crop yields. This call for farmers to adopt integrated soil fertility management (ISFM) practices to improve nutrient availability and crop yields. The use of ISFM has been reported to increase maize yields by 15–145% in semi-arid areas. Maize yields varies from 4200 to 5500 kg ha−1 and sorghum from 690 to 3500 kg ha−1 under ISFM. Yield increment for various crops with the use of cattle manure integrated with other nutrient sources was reported but there are still few studies where effects compost, farmyard manure and poultry manure were combined with inorganic fertiliser were evaluated. Therefore, this review paper seeks to synthesise the effects of ISFM practices available for smallholder farming systems in semi-arid areas of sub-Saharan Africa to improve crop production.