Response of mungbean genotypes to Rhizobium inoculum and varying levels of nitrogen fertilizer

To evaluate the effect of rhizobial inoculation and nitrogen fertilizer combinations on two mungbean genotypes, nodulation, nitrogen fixation, growth and yield, an experiment was conducted on Research Farm of University of Arid Agriculture, Rawalpindi. Mung varieties NM-92 and NCM-209 were sown in July 2000 in split plot arrangement-keeping varieties in main plot and fertilizer inoculation treatments in sub plots. The treatment combinations compared against control were inoculation, 30, 60 and 90 kg N per ha alone and in combination with inoculation. The observation recorded were days to flower initiation, flower completion and crop maturity, nitrogen content of soil, nodules, plant shoots, seed per pods, 100-seed weight, seed yield and harvest index. Economic analysis was also performed. The results of the study showed that interaction of genotype with nitrogen management were significant for N content of shoots, number of seeds per pods and N-content of soil after harvest. The combination of inoculum + 30 kg N per ha gave the highest N-content of shoot in NCM-209 which was significantly higher than all the other treatment x genotype. NCM-209 produced maximum number of pods per plant in response to inoculation + 30kg N per ha. Maximum N content of soil were found in plots where NCM-209 was treated with inoculation + 90N kg per ha. NCM-209 took more days for flower initiation, flower completion and crop maturity as well as increased economic yield as compared to NM-92 while NM-92 gave significantly higher N-content of nodules, and increased 100-seed weight as compared to NCM-209. The flower initiation, flower completion and crop maturity was delayed by nitrogen fertilizer and its combination with inoculation. Inoculation thus saved up to three days in crop rotation as compared to all the other treatments. Plots treated with seed inoculation + 30 kg N per ha produced maximum number of pods per plant, number of seeds per pod, 100-seed weight, economic yield and harvest index while the values recorded for control remained lowest for all the variable.