Implications of seed irradiation with γ-rays on the growth parameters and grain yield of faba bean

Faba bean productivity is highly influenced by N-inputs; yet, mineral N-fertilizers might undergo rapid leaching in light textured soils. On the other hand, these mineral fertilizers are more preferable than organic N-sources to raise protein content in bean seeds. Thus, the current study investigates to what extent organic fertilizers can partially substitute chemical N-inputs to satisfy plant needs for nutrients. Also, irradiating seeds is another approach to increase plant productivity by inducing further nutrient carriers to raise the effectiveness of the applied N-fertilizers. These two approaches were used in combination, in this study, to increase bean productivity grown on a poor fertile light textured soil (90.5% sand). To fulfill this aim, a field experiment was carried out during the winter season of 2017/2018 following a split plot design where the different N-sources (organic vs inorganic and mixtures of these two N- sources, all applied at the recommended dose i.e. 48 kg N ha-1) were plotted in the main plots while γ-irradiated seed treatments were plotted in the subplots. Irradiating bean seeds with gamma rays at a rate of 20 Gy (the least dose) increased significantly NPK uptake by beans and also enhanced plant growth. This consequently raised significantly the grain yield; however, increasing the dose of seed irradiation (>20 Gy) lessened significantly plant growth parameters and seed yield. The combined N-treatments also raised considerably NPK uptake by bean and recording the highest significant increases in plant growth parameters and grain yield. Moreover, mixed treatments recorded comparable protein contents in bean grains vs plants received 100% ammonium sulphate. Combination between seed irradiation and mixed N-sources were of positive effect on plant growth parameters and grain yield at only 20 Gy, while these parameters decreased considerably thereafter. In conclusion, seed irradiation may be a useful technique to increase legume plant growth; however, slight increases in the used dose may negatively affect the total quantity of the grain yield. The aforementioned results highlight the importance of amending light textured soils with the mixed (organic+mineral) N-sources to increase the productivity of faba bean grown on a such soil.