GROWTH AND YIELD RESPONSE OF SCREENED SOYBEAN (GLYCINE MAX (L.) MERRIL) GENOTYPES TO FERTILIZATION AND RHIZOBIA INOCULANTION IN NORTHERN GHANA

Abstract

Soybean remains an important crop for the sustenance of livelihoods of resource-constrained farmers in northern Ghana. However, yield of the crop has continuously remained low due to poor soil fertility and low productivity. A two-phase experiment was carried out during the 2019 cropping season to evaluate the growth and yield response of screened soybean genotypes to nitrogen, phosphorus and rhizobia inoculation. In the first phase, growth and yield of 100 selected genotypes were studied under optimum phosphorus fertilization using the lattice design. In the second phase, 3 best performing genotypes (N19, N119, N135), selected in phase one together with a known variety (Jenguma) were accessed for growth and yield under phosphorus, nitrogen and inoculants using a 4 (genotype) x 7 (nutrient regime) split plot design. The nutrient regimes were sole triple super phosphate (TSP), sole inoculant, sole booster nitrogen, TSP + booster nitrogen, TSP + inoculant, TSP + booster nitrogen + inoculant and a control (No fertilizer). Each treatment was replicated three times. Data collected were subjected to analysis of variance and means separated at 5% probability using the least significant difference. The results showed that plant height, days to 50% flowering, number of unfilled pods and 100 grain weight were significantly influenced by genotype. Number of nodules, biomass dry weight and pod weight were significantly affected by the nutrient regime. Leaf area, number of leaves per plant, number of primary branches and number of effective nodules were significantly affected by both genotypes and fertilizer regime. Genotypes N135, N119 and Jenguma flowered almost at the same time (from 42 to 43 days after planting) whereas genotype N19 took a longer period to flower. There was a significant (P = 0.032) interaction effect between genotype and nutrient regime on grain yield. Jenguma, treated with TSP+ inoculant recorded the highest yield of 4 t/ha followed by Jenguma variety treated with TSP + inoculant + booster nitrogen (3.9 t/ha) and genotype N135 treated with TSP + nitrogen (3.7 t/ha) while genotype N19 without treatment (control) recorded the least grain yield. The high yield obtained for inclusion of P, N and inoculants exceeded what is documented for northern Ghana (1.5 t/ha). It is recommended to farmers to include P, booster N and inoculants in cultivation of the Jenguma variety. Based on economic cost analyses, farmers stand to achieve higher profit upon application of sole TSP. Sole TSP is therefore recommended to maximize profit.