مقایسه عملکرد و کارآیی مصرف آب سه رقم نخود در شرایط دیم و آبیاری تکمیلی

Introduction
Chickpea (Cicer arietinum L.) is one of the oldest pulses crops in the world and one of the seven Neolithic founder crops in the Fertile Crescent of the Near East. Chickpea cultivars are grown mainly in the Mediterranean area, the Near East, Central Asia and America. In Iran, chickpea seeds are usually consumed in the form of mature, dry seed after cooking and processing in different ways. A total pulse crop cultivation area in Iran is nearly 770000 hectares and 61% of this amount is earmarked for chickpea. The chickpea is a good source of carbohydrates and protein, and 83.9% of the total constituent carbohydrates makeup from starch. Supplemental irrigation can be practiced to achieve the best yield with the least quantity of water available during reproductive periods. The effects of supplemental irrigation in chickpea showed that supplemental irrigation would improve chickpea growth and increase yield especially under dryland conditions (<500 mm).
 
Materials & Methods
This field experiment was conducted at the Rozve Experiment Station, at Agriculture and Natural Resources Research Center (32°50´ N, 50°34´ E), Esfahan, Islamic Republic of Iran, 17 Km north of Eastern of Chadegan  in one cropping season (2014) on a sandy loam soil (EC=3.78 dS m-1, pH=7.7 and OM=0.55%). In rotation before the chickpea, wheat was cultivated. The experiment was conducted as a split plot arranged in a randomized complete block design with four replications. Two methods of planting included of rainfed and one supplemental irrigation were considered as the main plot and three new varieties of peas (Hashem, Azad, and Arman) and local control varieties were subplots. Before planting the seeds of all varieties (prepared by the Department of Dryland Research Sara Rud) were sterilized with fungicides benomyl 2 per 1000. The weed control was done manually in the spring. Based on soil test results, there was no need for phosphate and potassium fertilizers. Water productivity (based on irrigation (WPI) + rainfall (R) were computed as: WPI (kgm−3) = Grain yield (kg ha−1)/Irrigation water applied +Rainfall (m3). The data were subjected to analysis of variance by SAS and means Fisher’s Protected LSD (5%) was used for mean comparison.
 
Results & Discussion
Based on this study, two methods of planting in terms of yield, yield components, and water use efficiency were significantly different. Plant height ranges changed from 28.2 cm in Azad (rainfed) to 40.6 cm in Arman (supplementary irrigation). Although plant height in all three experimental varieties in cultivation methods with supplementary irrigation was higher than rainfed conditions, but in both methods of cultivation, plant height in Arman cultivar significantly increased compared to the other two varieties. However, the effect of water stress on plant height depends on the stage of water stress. Plants grown with supplemental irrigation has more height than plants grown under dryland conditions. Azad varieties in rainfed and supplemental irrigation with 605.7 and 899.8 kg ha-1 respectively, had significantly higher yield than other cultivars (P≤5%). Inadequate supply of assimilates required for the development of seeds and embryos, is the reason for the decline in grain yield under dryland conditions. Number of pods per plant, is one of the most important yield components of chickpea. In this study, the number of pods under rainfed conditions was reduced 19, 15.5 and 17.6 percent in Azad cultivars, Hashem and Arman, respectively in comparison with supplemental irrigation. Regardless of the variety, harvest index under rain fed conditions showed a significant increase compared with supplemental irrigation and Azad cultivar with harvest index equal to 34.5, had the highest harvest index. Three varieties of Azad, Hashem, and Arman, for every millimeter of supplemental irrigation produced 5.88, 4.86 and 5.44 Kg extra yield (relative to rainfed conditions), respectively.
 
Conclusion
Based on the results of this study, chickpea cultivation especially with use of supplemental irrigation can improve grain yield than dryland conditions. Among the cultivars used in this experiment Azad cultivar both in rainfed and supplemental irrigation can be recommended.