Comparative analyses of the nitrogen fixing potential of different legume species grown under different agronomic practices

MSc (Crop Science), North-West University, Mafikeng Campus, 2017Biological nitrogen fixation (BNF) is an ecologically and economically beneficial process that can reduce the use of costly conventional inorganic nitrogen (N) fertilisers. This study was therefore conducted to assess the N fixing potential of four different legumes grown under different agronomic practices such as inoculation and fertilisation under both glass house and field conditions. One rainfed field trial and one glasshouse experiment were conducted during 2013/14 summer cropping season at the Agricultural Research Council- Grain Crops Institute (ARC-GCI), Potchefstroom. Treatments consisted of four legume species namely, cowpea, dry bean, groundnut and soya bean. These legumes were fertilised, inoculated, and fertilised + inoculated. Control plots with neither fertiliser nor inoculation were also included as standard checks. The different legumes were fertilised at optimum recommended rates for P and K, while N was only applied to specific treatments to determine the minimum accretion of whether nitrogen would have influence on nodulation and productivity. The legumes were inoculated with the rhizobium inoculant registered for each respective crop. The sources of N, P and K were limestone ammonium nitrate, superphosphate and potassium chloride, respectively. All the treatments were replicated four times and were arranged in a randomised complete block designin factorial arrangement ( 4 legumes x 2 inoculants x 2 fertiliser = 16 treatments) in all experiment. Data collected included total number of nodules, viable and non-viable nodules, ¾N, ¾C, ¾Ndfa, total amount of nitrogen in the plant, total amount of nitrogen fixed and seed yield. The treatment effects showed statistically significant differences (P