Biochemical and agronomic responses of guar to nitrogen, Bradyrhizobium inoculation and deficit irrigation under arid and semi-arid conditions
摘要
The present study aimed to investigate the effects of various levels of chemical nitrogen fertilizer and inoculation with different strains of Bradyrhizobium japonicum on several phenological, quantitative, qualitative, and fodder-related characteristics of guar (Cyamopsis tetragonoloba L.) under varying water-deficit regimes. A two-year field experiment (2021–2022) was conducted as a split-factorial arrangement based on a randomized complete block design with three replications to evaluate the interactive effects of nitrogen fertilization (0, 50, and 100 kg ha− 1) and seed inoculation with strains RS-150 and RS-153 under different irrigation regimes. Deficit irrigation significantly reduced grain yield, while full irrigation × 100 kg N ha− 1 yielded the highest GY (3658.2 kg ha− 1) and severe deficit × no N applicatopn the lowest (1017.8 kg ha− 1). Application of 100 kg N ha− 1 increased GY by 30.99% compared with the control. Inoculation with RS-153 enhanced grain number per m² and 1000-grain weight by 14.41% and 14.54%, respectively, relative to non-inoculated plants. Full irrigation also increased grain protein content by up to 22.19% compared with severe deficit. Soluble sugars accumulated under water stress, reaching 490.16 µg g− 1 DW under deficit irrigation × 100 kg N ha− 1 × RS-150, indicating osmotic adjustment. Crude protein, metabolizable energy, and dry matter digestibility were further improved under full irrigation and higher nitrogen supply. Overall, integrated nitrogen management and rhizobial inoculation partially mitigated drought-induced yield reductions and improved the forage quality of guar under semi-arid conditions.