Organic fertilizers improve the growth, seed quality and yield of newly released soybean (Glycine max (L.) Merrill) varieties in the tropics

Soybean (Glycine max (L.) Merrill) yield in tropical Africa remains below 1 t/ha partly because most growers rarely use beneficial organic soil amendments on degraded tropical soils. Therefore, field trials were conducted during the late cropping seasons (July–November) of 2015 and 2016 on the organic research plots of the Institute of Food Security, Environmental Resources and Agricultural Research, Nigeria (7° 13′ 51.17″ N and 7° 13′ 53.16″ N and longitudes 3° 23′ 49.12″ E and 3° 23′ 51.86″ E 131.5 m above sea level), the trials evaluated the agronomic response of five recently released soybean varieties (TGx 1448-2E, TGx 1440-1E, TGx 1740-2F, TGx 1987-62F, and TGx 1835-10E) to the application of three organic fertilizers (Aleshinloye grade B, Organo Farm, and Gateway) and a control. The trials were laid out in randomized complete block design (RCBD) in a 5 × 4 factorial arrangement and replicated three times. Data were collected on growth parameters, yield and yield attributes, and seed quality. Significant (p < 0.05, F test) varietal difference was recorded for aboveground plant weight, grain filling period, height at physiological maturity, number and weight of pods, number of branches and seed yield, and quality in both years. Application of organic fertilizers significantly (p < 0.05, F test) increased aboveground plant weight, number of branches and pods per plant, weight of seeds per plant, seed yield, and quality in both years relative to the control treatment, except oil content and seed yield in 2016. It is recommended that the three organic fertilizers can be used for soybean cultivation since soybeans grown on treated plots produced seed yield above 1/ton in both contrasting years of experimentation.