Effect of inoculation and fertilizer application on nitrogen fixation in bean

The legume family is comprised of a highly diverse set of plant species essential to animal and human nutrition. The introduction of effective strains of nodule bacteria during bean sowing increases nitrogen fixation and enables these plant species to be grown even on less fertile soils. This paper has studied the effects of inoculation and fertilization on nitrogen fixation parameters in the bean variety Belko. Sowing was done by hand and the seeds were inoculated using the microbiological fertilizer NS-Nitragin which contained a mixture of Rhizobium leguminosarum bv. Phaseoli strains specific to bean as a crop species. Both the bean genotype and NS-Nitragin fertilizer used originate from the Institute. Plant dry matter mass and nitrogen content were determined at flowering, while grain dry matter mass per plant, number of pods formed, and grain number per pod were measured at physiological maturity. The basic agrochemical soil analyses were performed just before sowing, at flowering and at physiological maturity. Plant nitrogen was determined according to Kjeldahl. The trial was established at the Rimski Šančevi Experiment Field and the trial treatments were as follows 1) 0 kg/ha + HR + 50 kg/ha N every three years; 2) 50 kg/ha + HR + 50 kg/ha N every three years; 3) 100 kg/ha + HR + 50 kg/ha N every three years; 4) 50 kg/ha + HR + 50 kg/ha N every three years; 5) 200 kg/ha + HR + 50 kg/ha N every three years; 6) 250 kg/ha + HR + 50 kg/ha N every three years; 7) 0 kg/ha; 8) 100 kg/ha; and 9) 200 kg/ha. No NPK mineral fertilizers were incorporated and the phosphorus and potassium rates were the same (80 kg/ha P2O5 and K2O) in all of the treatments. In treatments 1 through 6 harvest residues (HR) were incorporated by plowing under, and every three years 50 kg/ha N were added after wheat. In treatments 7, 8 and 9 harvest residues were removed. Each treatment consisted of an inoculated and a noninoculated version. The study results showed that inoculation had a positive effect on the symbiotic association parameters concerned, i.e. the plant length, dry matter mass, pod number per plant, grain number per pod and plant nitrogen content of the inoculated plants from all of the treatments were on average greater than those of the noninoculated ones. The different fertilization treatments had different effects on the effectiveness of the symbiotic association as well. The amount of nitrogen fixed ranged from 13.68 to 68.97 kg N/ha, averaging 23.31 kg N/ha. No nitrogen fixation occurred in treatments 5 and 9.