Effect of irrigation levels and spraying of chemical fertilizers on some physiological traits and grain yield in castor (Ricinus communis L.)

castor bean (Ricinus communis L.), is an oilseed of relevant economic and social importance. From its seeds is extracted an oil of excellent properties, having wide use as industrial input and several applications. It is cultivated since the times of the ancient civilizations, the castor bean is a rustic plant, resistant to drought, belonging to the family of Euphorbiaceae, The purpose of this investigation was study effect of irrigation levels and spraying of chemical fertilizers on some physiological traits and grain yield in castor. Drought stress, in addition to the negative effect on yield, causes or exacerbates other stresses, especially the stress of nutrient deficiencies for the plant. This experiment was conducted in East Azarbaijan Agricultural Research and Education Center, Tabriz- Iran at 2017 crop season. Field experiment was carried out by a split plot design based on completely randomized block design with three replications. The first factor included irrigation levels including control (normal irrigation), irrigation after 80 mm and 140 mm evaporation from the pan evaporation in the main plot and eight spraying chemical fertilizers including sulfur, potassium, nitrogen, sulfur + potassium, sulfur + nitrogen, potassium + nitrogen, sulfur + potassium + nitrogen and control as spraying in sub plots. In this study, plant height, chlorophyll index, leaf area index, leaf weight, leaf temperature, water relative content (RWC), relative growth rate (TGR), number of pods, biological yield and grain yield were measured. Also Traits were analyzed by using SAS 9.2 software and means comparison was tested by least significant difference (LSD). The results showed that the effect of irrigation levels on all traits was significant, there was a significant difference between spraying chemical fertilizers in terms of all traits except relative growth rate, furthermore the interaction of two treatments was significant on all traits except chlorophyll index, leaf area index, leaf temperature and leaf relative water content. Mean comparison of irrigation treatments showed that irrigation after 140 mm evaporation decreased the chlorophyll index, leaf area index and leaf relative water content compared to normal irrigation (control) 77.12, 48.86 and 16.85 percent respectively and increased the leaf temperature by 17/33 percent, Also, the increase of chlorophyll index, leaf area index and leaf relative water content in S + N + K fertilizer spraying treatments were 13.48, 38.29 and 73.7%, respectively, and the leaf temperature decreased by 25.25% in comparison with control treatment (non-spraying). In this study, the highest plant height, leaf weight, relative growth, pod number, biological yield, and grain yield by average of 111.67 cm, 13.63 grams, 0.009 grams per day, 79.38 pods, 5 tons per hectare and 53.1 tons per hectare was assigned to normal irrigation and spraying chemical fertilizers of K + S + N . According to the results of this study, it can be stated that, S + N + K spraying had a positive effect on the increase of yield components and grain yield. Also, this treatment was able to moderate the effects of drought stress on yield and yield components. So S + N + K fertilizer application is recommended for achieving high grain yield in castor