Effect of Soil Moisture Status on Growth, Development, Yield and Seed Quality of Bambara Groundnut (Vigna Subterranea (L) Verdc.)

Abstract

Studies were conducted from October, 2001 to June, 2002 at Crop Science Department, University o f Ghana, Legon, to determine the effect o f soil moisture on growth, development, yield and seed quality o f bambara groundnut ( Vigna subterranea (L.) Verde.), using two varieties: Jabajaba and Chichele Balgu. Three soil moisture regimes, viz. 30-40%, 50-60% and >70% o f field capacity were imposed two weeks after planting till final harvest. L eaf number, leaf area, nodule number, dry m atter production, pod yield and harvest indices decreased significantly at 30-40% moisture level, with 50-60% recording the highest values for these parameters in both Jabajaba and Chichele Balgu. Pod and seed yields were similar at 30-40% and >70% moisture regimes, and these were significantly lower than at 50-60% moisture regime. The 50-60% moisture was m ost effective in terms o f grain yield and dry matter production in bambara groundnut. Although Jabajaba demonstrated better adaptation to moisture stress and higher yield potential than Chichele Balgu did, reproductive yield was generally low, largely due to poor partitioning o f dry m atter into seeds as expressed in their harvest indices. Qualitative assessments o f seeds revealed that soil moisture had significant effect on seed size, protein and tannin contents. Hundred-seed weight was lower at 30-40% moisture than at >70% moisture, but highest at 50-60% moisture. The protein content at 30-40% moisture was higher than protein content at >70% moisture, but lower than protein content at 50-60% moisture. However, protein content in Jabajaba was higher than in Chichele Balgu, whilst the level o f tannins was higher in Chichele Balgu than in Jabajaba. The tannin content was lower at >70% moisture than at 50-60% moisture, whilst 30-40% m oisture recorded the highest. M oisture regime o f 30-40% was detrimental to growth, development, yield and seed quality o f bambara groundnut. Hence, optimum m oisture conditions seem very necessary for good quality seed production in bambara groundnut. Selecting varieties with high protein and low tannin contents and growing them under optimum moisture and climatic conditions will improve the quality o f bam bara groundnut. Cream seeded varieties (Jabajaba) seemed most promising and viable alternative to improve the diet o f m en and animals.