Response of Soybean (Glycine max L.) Genotypes to Application of Lime and Phosphorus on Acidic Nitisol of Mettu, South Western Ethiopia

Abstract

Soybean (Glycine max L.) is one of the most important oil crops and it is the world’s leading source of oil and protein among food legumes. Acidic soils limit the productive potential of crops because of low availability of basic cations and excess of hydrogen and aluminium in exchangeable forms. In Ilu abba bora Zone, soil acidity is a well-known problem limiting crop productivity. This study was conducted to assess the response of soybean genotypes to lime and phosphorus for some of the important growth, root and nodulation characteristics and yield and yield components and to identify soybean genotypes that tolerate low pH soil. Treatments were laid out in a split-plot design, whereby four soil amendments were assigned to main plots i.e. control, lime alone (3457.8 kg ha-1 ), phosphorus alone (20 kg ha-1 ) and both lime and phosphorus (3457.8 +20 kg ha-1 ) and fifteen genotypes were assigned to the subplots. Data on growth, root and nodulation characters, yield and yield components, and soil parameters were collected and analyzed using SAS version 9.3 software. Treatment means were compared at 5% level of significance using Duncan’s Multiple Range Test. The results revealed that genotype x amendment interactions were significant (p<0.01) for all growth, root and nodulation characteristics and yield and yield components, except for hundred seed weight where only the main effects of genotypes and amendments were significant. The maximum grain yield of (2120 and 2047.2 kg ha-1 ) was obtained under Phosphorus alone and combine with lime from HAWASSA-04 variety and PI567046A genotype, respectively with non-significant variation; while the lowest (510.5 kg ha-1 ) were recorded from SCS-1genotype under the control treatment. Tolerance index and mean productivity value indicated that genotype PI567046A and variety HAWASSA-04 performed well for most of the traits and selected as tolerant. Significant and positive correlations were found for all growth, root and nodulation parameters with grain yield. Yield was highly significantly and positively correlated with above ground dry biomass (r=0.82), shoot fresh weight (r=0.81) and shoot dry weight (r=0.76). The soil results revealed that soil pH increased from 4.40 to 4.90 pH while exchangeable acidity decreased from2.72 to1.52 cmol (+)/kg under lime alone, which resulted in improved soil chemical properties. The result of this study verified that application of lime (3457.8 kg ha-1 ) and Phosphorus (20 kg ha-1 ) improved the growth, root and nodulation characteristics yield and yield related traits of soybean genotypes. In conclusion, observation of large variation indicates that selection would be effective to improve soybean genotypes performance on acid soils and identify low Phosphorus tolerant genotype that helps smallholder farmers optimize soybean productivity on acid soils in the study area. HAWASSA-04 variety and PI567046A genotype are the most tolerant among the tested materials. However, further study is required including more locations and years by considering additional genotypes, to determine the residual effect of phosphorus and lime to reach at a conclusive recommendation