Stimulation of N-2-fixation in chickpea by gamma irradiation as affected by different levels of ammonium sulfate fertilizer

A pot experiment was conducted under natural climatic conditions to study t he effect of low doses of gamma irradiation (0, 5, 10, and 20 Gy) on the pe rformance of winter chickpea (Cicer arietinum L.) in the presence of increa sed supply of N-15 labeled ammonium sulfate (0, 20, 50, and 100 kg N ha(-1) ). Presowing seed irradiation produced a significant increase in dry matter production (up to 36%) and total nitrogen yield (up to 45%). The stimulati ve effect of irradiation was more pronounced with the application of NH4+-N fertilizer. Seed irradiation increased the amount of N-2-fixation by 8-61% depending on the dose and level of NH4+-N fertilizer rate. A 10 Gy was fou nd to be the optimal irradiation dose for enhancing N-2-fixation. High leve ls of NH4+-N decreased the percentage and the amount of N-2-fixation, but d id not affect nodule formation. However, the presowing 10 Gy irradiation do se reduced the negative effect of ammonia-N fertilizer on N-2-fixation. The refore, we recommend irradiating chickpea seeds with a 10 Gy dose before pl anting in soil containing high levels of mineral nitrogen to reduce its neg ative effect on N-2-fixation.