اثر کائولین، کیتوزان، کلریدکلسیم و سلنات سدیم بر رشد، اجزای عملکرد و عملکرد نخود زراعی تحت آبیاری تکمیلی

Introduction
Chickpea (Cicer arietinum L.) is one of the most important grain legumes, which is cultivated in most parts of the world, especially in arid and semi-arid regions because of its strategic importance in plant protein production. Among environmental stresses, drought stress limits plant growth and crop production more than any other factor. Many reports indicate that drought stress at the end of the season is the cause of a severe decrease in grain yield of chickpea in most regions, especially in Iran. Terminal drought, depending on the geographical area and weather conditions reduces 30 to 60 percent of the yield. With the improvement of crop management methods, such as breeding methods and using drought stress tolerant cultivars, it is possible to ameliorate the reduction of yield due to drought stress. On the other hand, application of supplemental irrigation at some stages of plant growth is a management factor for improvement, stability and finally reduction of risk for crop production under drought stress conditions. By increasing the intensity of drought stress, the plant development stages occur faster and the number of days to flowering, podding and maturation decreases. Drought stress decreases the area and weight of leaves. The results of the experiments indicated that drought stress caused a significant decrease in grain yield and yield components of chickpea. One way to reduce the adverse effects of drought stress on plants is reducing transpiration rates. In recent years, transpiration alleviator substances have been considered as a solution to reduce water losses from plant, because they reduce the rate of water vapor release from the leaves. Also, stress ameliorator substance such as calcium chloride and sodium selenate play an important role in adaptation of cells to abiotic stresses and increase the activity of antioxidants anzymes and photosynthesis through water absorption, root growth and maintaining turgor pressure in plant cells. The aim of this study was to investigate kaolin and chitosan as transpiration alleviator substances as well as calcium chloride and sodium selenate stress ameliorators on growth, yield and yield components of Azad chickpea cultivar under different irrigation regimes.
 
Materials & Methods
Effects of kaolin, chitosan and drought stress ameliorators on crop growth rate, grain yield and yield components of chickpea were investigated under supplemental irrigation at Hamedan Agricultural and Natural Resources Research Center during 2014-2015 growing season. A factorial split plot experiment basesd on a completely randomized block design with three replications were used. Three supplemental irrigation regimes, including irrigation at flowering stage, irrigation at podding stage and two irrigation flowering+podding stages with non irrigation (rainfed) in main plots and transpiration alleviator substances (kaolin 5%, chitosan 200 mlL-1) and stress ameliorators (chloride calcium 5 mM, selenat sodium 40 mlL-1) with non spray (control) treatments as factorial were placed in sub plots. Seeds were cultivated with 30 cm row spacing and 31 plants per m2 density at 5 cm depth of soil on March 5th. Application of stress ameliorators was performed in two stages before and after flowering. Spraying of anti-transpirations substances in the middle of the pudding stage was done by hand sprayed on the leaves. During this investigation, maximum leaf area index, maximum crop growth rate, biological yield, grain yield, yield components and harvest index of chickpea (var. Azad) were studied.
Results & Discussion
The results showed that the main effects of irrigation levels and transpiration alleviator substances in all studied traits, except to biological yield, also drought stress ameliorators except for seed number per pod were significant at the 1% level. The two and three interactions between studied factors were significant for different traits except to the number of seeds per pod. Foliar application of chitosan and calcium chloride in one irrigation at podding stage compared to irrigation at flowering stage or without irrigation (rainfed) increased seed yield by 42% and 192%, respectively. Also, spraying of chitosan with calcium chloride in two supplemental irrigation regime increased the grain yield comperad to one irrigation regimes at flowering or podding and rainfed by 99%, 41% and 312%, respectively. Two irrigation regimes with chitosan spray and calcium chloride consumption had the highest harvest index (50.3%) and in comparison to one irrigation regimes at flowering or podding and rainfed increased harvest index by 33%, 15% and 85%, respectively. Two irrigation regimes with chitosan and calcium chloride application had the maximum crop growth rate of plant and in comparison to one irrigation regime at flowering, podding stages and rainfed increased by 31%, 19% and 104%, respectively. In the two irrigation regimes with chitosan foliar and calcium chloride consumption, the maximum leaf area index was increased as compared to single irrigation regimes in flowering or podding stages and without irrigation.
 
Conclusion
Based on the present study, if sufficient water is available, it is preferable to use a double irrigation regime at flower and pod stages or at least a single irrigation regime in the podding stage with the spray of chitosan and calcium chloride to increase the grain yield of the chickpea (var. Azad) is recommended.