Introduction
Chickpea (Cicer arietinum L.) is an important grain legume cultivated in arid and semi-arid regions worldwide. Water deficit, particularly terminal drought stress, is one of the primary factors limiting chickpea productivity and grain yield. Supplemental irrigation can alleviate drought stress during critical growth and developmental stages, thereby enhancing crop yield. Irrigation applied at sensitive stages such as flowering, pod formation, and grain filling has been shown to improve yield and its components. Therefore, the present study aimed to evaluate the effects of supplemental irrigation on grain yield and water-use efficiency of different chickpea genotypes and to identify the most promising genotype under the studied conditions.
Materials and Methods
This study was conducted as a split-plot experiment based on a randomized complete block design with four replications at the research farm of the Faculty of Agriculture, University of Zanjan, Iran, during the 2020 growing season. The main plots consisted of three irrigation regimes: full irrigation, supplemental irrigation, and rainfed conditions. The subplots included four chickpea genotypes: Azkan, Mansour, Adel, and Saeed. In the supplemental irrigation treatment, water was applied at two critical growth stages, namely flowering initiation and pod formation. At the end of the growing season, several agronomic traits were evaluated, including plant height, number of secondary branches, number of seeds per plant, hundred-seed weight, biological yield, grain yield, harvest index, grain and biological water-use efficiency, and irrigation water-use efficiency.
Results and Discussion
The highest number of seeds per plant was recorded under full irrigation and supplemental irrigation treatments. Among the studied genotypes, Azkan produced the greatest number of seeds per plant, whereas Saeed produced the fewest. The highest 100-seed weight was obtained under full irrigation, with significant reductions observed under supplemental irrigation and rainfed conditions. The decline in seed weight under drought stress may be attributed to reduced cell division, lower photosynthetic activity, and decreased activity of enzymes involved in the synthesis of seed storage compounds. Biological yield decreased under supplemental irrigation and rainfed conditions compared with full irrigation. This reduction can be explained by the decline in source strength resulting from limited soil moisture availability. Analysis of the irrigation × genotype interaction for grain yield revealed a substantial reduction in grain yield for all genotypes under rainfed conditions relative to full irrigation. Compared with full irrigation, the Azkan and Adel genotypes exhibited greater yield reductions under supplemental irrigation. Drought stress adversely affected grain yield by restricting leaf growth and development, reducing photosynthetic activity and source strength, and decreasing the number of flowers, pollination success, and fertile pods. In addition, drought reduced the accumulation of assimilates in developing seeds, thereby diminishing sink strength and ultimately lowering grain yield. Nevertheless, supplemental irrigation significantly increased grain yield compared with rainfed conditions. The interaction effect of irrigation regime and genotype on grain water use efficiency indicated that the highest water use efficiency was achieved by the Mansour genotype under supplemental irrigation, whereas the lowest water-use efficiency was observed under rainfed conditions. Grain water use efficiency increased under supplemental irrigation in all genotypes; however, the magnitude of improvement differed among them. Mansour and Saeed showed the greatest increases in grain water use efficiency. Irrigation water use efficiency for grain yield also improved under supplemental irrigation across all genotypes. Among the evaluated genotypes, Mansour exhibited the highest irrigation water use efficiency, while Adel showed the lowest under supplemental irrigation conditions.
Conclusion
Supplemental irrigation applied at the flowering and podding stages significantly increased grain yield and water use efficiency compared with rainfed conditions. Moreover, supplemental irrigation proved to be more effective than both rainfed and full irrigation in terms of optimizing crop productivity and water use efficiency. Among the genotypes, Mansour exhibited the highest grain yield and water use efficiency under both full and supplemental irrigation regimes. Therefore, this genotype can be recommended for cultivation in the Zanjan region, particularly under conditions where efficient water management is a priority.