Abstract
About 70% of the groundnut (Arachis hypogaea L.) produced in Ghana is from the Guinea savanna. However, low soil nutrients, especially N, together with erratic rainfall distribution have often resulted in poor grain yield. The aim of this study was to evaluate plant growth, N2-fixing efficiency, N contribution, water-use efficiency and pod yield of 21 elite groundnut genotypes in the Guinea savanna of Ghana, using the 15N natural abundance technique. The data revealed significant variations in plant growth, symbiotic N contribution, and pod yield among the 21 genotypes tested at each field site. Average N contribution by groundnut genotypes ranged from 48 to 108 kg N ha−1. Also, mean pod yield ranged from 0.58 to 2.1 t ha−1. Genotypes ICGV-IS 08837, ICG 6222, ICGV 03315 and NKATIESARI demonstrated superior plant growth, symbiotic N contribution and greater pod yield. In fact, ICGV-IS 08837 yielded almost 2.5 fold more than CHINESE which is the most widely cultivated variety in the region. Genotypes ICGV-IS 08837, ICG 6222, ICGV 03315 and ICGV 99247 are therefore recommended for development into varieties for the Guinea savanna of Ghana. Genotypes ICG (FDRS) 4, ICGV00362 and ICGV99247 exhibited increased water-use efficiency, but were low in N2 fixation and N contribution, and would therefore be good parental material in breeding programs aimed at enhancing water-use efficiency in high N2-fixing genotypes.
Highlights
Nitrogen (N) is an important component of plant growth and is needed for the biosynthesis of amino acids and proteins (Nelson et al 2008) as well as chlorophyll for CO2 assimilation (Lawlor 2002)
Increased crop yields in the Guinea savanna of West Africa is constrained by low soil fertility (Cofie et al 2005; Kombiok et al 2005)
21 elite groundnut genotypes were assessed for N2 fixation, N contribution, grain yield and water-use efficiency using the 15N natural abundance
Summary
Nitrogen (N) is an important component of plant growth and is needed for the biosynthesis of amino acids and proteins (Nelson et al 2008) as well as chlorophyll for CO2 assimilation (Lawlor 2002). In Ghana, N and P are the most limiting plant nutrient in the Guinea savanna agro-ecology (Ahiabor et al 2011). Groundnut is the most important grain legume in Ghana, and is largely cultivated in the Guinea savanna agro-ecology, which accounts for more than 70% of the national production (Tsigbey et al 2003; MoFA-SRID 2014). This agro-ecology is characterised by acidic soils (pH 5–6.5), that are low in organic matter and N due to annual bush burning and crop residue removal (Abubakari et al 2012). The use of chemical N fertilisers can overcome N deficiency but they are expensive, Oteng-Frimpong R., Dakora F.D
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