Effects of Liming on Nodulation, Nitrogen Fixation and Seed Protein Content in Soybean

Soil acidity is influenced by high levels of aluminium, iron, manganese and low levels of Cation Exchange Capacity (CEC), plant nutrients availability such as phosphorus, affect the growth of symbiotic-fixing bacteria in soybean which is detrimental to nodule formation and functioning. In an attempt to evaluate liming effects on soil pH, nitrogen fixation and seed protein content, an experiment was set up using a randomized complete block design (RCBD) layout in a split-plot with four replications at the Crop Museum, the Sokoine University of Agriculture in Morogoro, Tanzania. Soybean genotypes (Bossier, Laela and Uyole soya-1) were used as the main plot, while lime levels (1560, 936 and 624 kg/ha) were used as the subplot. The analysis of variance (ANOVA) showed a significant influence of lime levels on soil pH, quantities of nitrogen fixed and seed protein content. There was a significant difference (P = 0.001) observed among soybean genotypes with the application of 1560 kg/ha of lime (pH 6.5), recording the highest (7.6) nodule counts and nodule dry weight (19.26). Among the different varieties used in the study, Bossier was observed to have a fixed 24.46 kgN/ha, while Laela produced the highest (10.60%) seed protein content. Application of 1560 kg/lime observed a significant increase in kgN/ha (35.71) as well as a minimal increase (15.66%) in seed protein content at pH 6.5. Interaction effects (P = 0.05), however, observed Laela has fixed the highest nodule (7.6) counts, nitrogen fixation (44.90 kgN/ha), with Bossier recording the highest (20.22%) seed protein. The study revealed that the physiochemical properties of acid soil, as well as soybean yield components such as nodules, N2 fixation and seed protein content, can be maximally improved when limed with CaCo3