Effect of Mulch and Selenium and Boron Foliar Spraying on Some Quantitative and Qualitative Characteristics of Sunflower (Helianthus annuus L.) in Saline Soil

Iran has a large surface area of saline soil and in this condition of saline soil, crop production is involved with a lot of problems including deficiency of some nutritional elements and outcome of this problems is decreasing of quantitative and qualitative yield. For this purpose, in saline soil conditions, an experiment was conducted to evaluate the effect of foliar spraying of selenium and boron elements, and mulches application of wheat straw and cow manure on some of sunflower properties. In order to evaluate the possibility of increasing the quantitative and qualitative yield of the product in saline soil conditions (At a depth of 0 to 60 cm, with an average electrical conductivity of 8.68 dS.m-1, pH of 7.85 and silty clay soil texture) a factorial experiment in a randomized complete block design with three replications was conducted on sunflower (Ghasem hybrid) in Khuzestan Agricultural Sciences and Natural Resources University in 2016. Treatments was included, three mulches (no application, wheat stubble 15 ton.ha-1 and cow manure 30 ton.ha-1), foliar spraying of selenium in the form of sodium selenite (no application, 17 and 34 mg.l-1) and boron foliar spraying in the form of boric acid (no application and 400 mg.l-1). Irrigation was done in a furrow. The traits that were studied included: seed yield, oil yield, seed protein percentage, selenium and boron content of seed, oil harvest index, seed harvest index, biological yield, number of seeds per capitulum and 1000-seed weight. The application of mulch, especially wheat mulch, in comparison with non-application of mulch, had a positive effect on most of the studied traits. The use of selenium significantly increased the content of selenium seed compared to its non-application so that the highest and lowest selenium seed content were observed in high (0.14 ppm) and low (0.12 ppm) levels of selenium foliar spraying treatments respectively. The main effect of boron foliar application were not significant on the studied traits, but its triple interaction with selenium foliar spraying and mulch on important traits such as seed yield, oil yield and harvest index were significant. Application of selenium significantly reduced the weight of 1000 seeds, so that the highest 1000-seed weight was obtained from the non-use of selenium (55.50 grams) and by increasing the concentration of selenium foliar spraying solution, 1000 seed weight (50.55 grams) decreased. The interaction effect of selenium and boron foliar spraying on seed number per capitulum was significant so that the lowest number of seeds per capitulum (1293) was obtained from non-use of selenium and boron which averaged more than 100 seeds less than other treatment compounds. The highest seed yield (6431 kg.ha-1) and oil yield (2529 kg.ha-1) showed in boron foliar spraying × wheat straw. Treatments had no significant effect on seed oil percentage (with mean of 35.78 %). The highest protein content (25/46 %) was obtained from treatment of wheat straw. Overall, in this experiment, non-selenium foliar spraying (17 mg.l-1) × boron foliar spraying (400 mg.l-1) × wheat straw mulch application had the best quantity and quality yield. According to the results obtained in saline soil conditions, the beneficial effects of wheat stubble mulch (significant increase in harvest index, number of seeds per head, grain yield and seed protein percentage compared to non- application) was more than expectation. However, suitable selenium concentration (17 mg.l-1) had beneficial effects but the higher level of selenium foliar application (34 mg.l-1) had a negative effect on quantitative and qualitative yield.