3. Enhancing Soil Productivity in Ghana through the Use of Leguminous Cover Crops and Tillage Practices

Abstract

Soil fertility in Ghana is low and rapidly declining due to inappropriate soil management practices. This review examines the role of leguminous cover crops and tillage practices in building and sustaining the fertility of soils for enhanced productivity. A trial in the forest zone of Ghana evaluated the effect of two main tillage practices {minimum (MT); full tillage (FT)} and 4 cropping systems; maize/mucuna + 30-20-20kg N-P₂O₅K₂O ha^-1(MMF1), maize/pigeon pea + 30-20-20 kg N-P₂O₅-K₂O ha^-1 (MPF1), maize/cowpea + 30-20-20 kg N-P₂O₅-K₂O ha^-1(MCF1), sole maize + 60-40-40 kg N-P₂O₅-K₂O ha^-1(SMF2), sole maize + 30-20-20 kg N-P₂O₅-K₂O ha^-1(SMF1). After 4 years of continuous cultivation, MPF1 under MT (3.41t ha^-1) and FT (3.45 t ha^-1) gave the highest maize yield. SMF1 (0.48 t ha^-1) gave the lowest grain yield. A separate trial in the forest zone on a 5^o slope showed that FT with sole maize and removal of maize stover resulted in significant soil lost (4.61t ha^-1) and low maize yield. (2.33 t ha^-1). FT under maize/cowpea rotation and incorporation of maize and cowpea stover, soil lost was significantly low (0.75 t ha^-1) with higher grain yield (4.23 t ha^-1). Low soil lost (0.37 t ha^-1) and high grain yield (4.34 t ha^-1) was also obtained under MT with maize/cowpea rotation with plant residue used as mulch. MT under sole maize with maize stover as mulch gave very low soil lost (0.27 t ha^-1) but maize yield was also low (2.4 t ha^-1). At Nyankpala after a two year callopogonium fallow maize was grown in the third year. MT with residue applied as mulch gave similar maize grain yield (4.1 t ha^-1) as FT and residue removed with application of 40 kg N ha^-1 (4.6 t ha^-1). In the Savanna zone, mucuna was intercropped with maize at three different stages. Maize grain yield was significantly higher for the control in the first year but the least in the third year. Maize yield was highest at 6 WAP in the third year. Inclusion of appropriate leguminous crops in cropping systems in Ghana with incorporation of plant residue or as mulch is recommended. Minimum tillage in combination with leguminous crops will minimize soil erosion and improve crop yields. These good options need scaling up for the improvement of soil productivity.