Growth and yield response of soybean [Glycine max (L.) Merrrill] to inoculation and starter N fertilizer applications in the Tolon District of the Northern Region of Ghana
An experiment was conducted at Nyankpala in the 2012 cropping season and repeated in the 2013 cropping season in the Tolon District of the Northern Region of Ghana. This was to ascertain the effect of N fertilizer and inoculant applications on the growth and grain yield of soybean (Glycine max [L.] Merrill). It was a 3 × 5 factorial experiment laid in Randomized Complete Bock Design (RCBD) with four replications. The factors were three soybean varieties (Jenguma, Quarshie and Anidaso) and four levels of N fertilizer (urea), which were 0, 15, 30 and 45 kg N ha-1 and inoculant. The inoculant was applied at the rate of 5 g to 1 kg of soybean seed through the slurry method that was estimated to give 107 of viable rhizobia cells. Planting was done on 14th and 10th July, 2012 and 2013, respectively, by drilling. Thinning was later done to two plants hill-1 at 10 cm within rows and 50 cm between rows with an approximate plant population of 400 000 plants ha-1. The N fertilizer was applied to randomly assigned plots 2 weeks after planting (2 WAP) in drills 5 cm away from the plants and covered. Growth parameters measured were plant height, leaf area, number of primary branches, nodule and shoot dry weights. Grain yield was measured from 2 m × 2 m net plot and extrapolated to kg ha-1. Results showed that all the varieties nodulated following the inoculation. It also showed that there was promiscuous nodulation where inoculants were not applied. The inoculated treatment produced greater plant growth, grain yield and the amount of N fixed than the uninoculated control. Growth and yield were greatest in the 30 and 45 kg N ha-1 treatment compared with the other treatments. The results showed that for profitable soybean production in the study area, inoculation or 30-45 kg N ha-1 fertilizer should be applied.