Evaluation of Rapeseed Oil Yield under Different Spraying Time of Boric acid and Zinc sulfate in Sistan Region

Rapeseed oil is the third source of vegetable oil in the world. It is considered as safe oil nutrition, due to its lowest and moderate content of saturated and unsaturated fatty acids, respectively. According to the latest statistical reports, its farming area are extending every year (has extended from 60 to 200 thousand hectares, in last year). Using of fertilizers in appropriate time and amount plays key role in production of high quality and quantity agricultural products. Therefore, in this research yield components and seed quality parameters have studied for revealing the best time of boric acid and zinc sulfate fertilization.
All of analysis steps were conducted in the Agricultural Research Institute, University of Zabol, Iran (UOZ). The boric acid and zinc sulfate spray effects on vegetative and reproductive stages of rapeseed were studied in a complete randomized block in factorial arrangement with three replications. Treatments were included foliar spraying in four levels: control (no spraying), boric acid (2 g l-1), zinc sulfate (2 g l-1) and both boric acid zinc sulfate (2 g l-1), and also time of foliar spraying were at 90 days after planting (vegetative stage), 120 days after planting (reproductive stage) and both vegetative reproductive stages. They were evaluated characteristics such as plant height, thousand–seed weight, seed yield, biological yield, harvest index, SPAD number, protein percentage, oil yield and percentage, seed and straw nitrogen percentage, boron uptake content in seed and straw, and finally zinc uptake content in seed and straw. Nitrogen, protein, Boron and zinc amounts were determined by keldal method, multiplying the percentage of nitrogen in 6.25, Azomtin-H method using spectrophotometer at 420 nm, and atomic absorption, respectively. Also, SPAD number value and oil content were measured by chlorophyll meter SPAD 502 Plus model and Soxhlet extractor, respectively. Statistical analyses were performed using SAS software and the means comparison was done using Duncan test at the 5% probability level.
Time of foliar spraying of vegetative reproductive showed significant different with other treatments for the most of study characteristics. The time of foliar spraying effect was significant on all of characteristics except thousand seed weight and SPAD number. Also type of foliar spraying showed significant effect on all of characteristics except SPAD number. It was observed Maximum seed yield (2610 kg ha-1), oil yield (1569.6 kg ha-1) and seed protein percentage (42.2%), respectively, in boric acid zinc sulfate and vegetative reproductive stage that increased 66.8%, 76.7% and 52.8% in compared to control. The maximum magnitude of seed and straw nitrogen uptake content with rate 6.7% and 2.9% were obtained from boric acid zinc sulfate in vegetative reproductive stage. Spraying of boron and zinc increased concentration of these nutrients with rate 36.3% and 39.2% in compared with control respectively.
The results of this study indicated, foliar spraying of both boric acid zinc sulfate (2 g l-1) in 90 days after planting (vegetative stage) and 120 days after planting (reproductive stage) stages in order to produce Rapeseed in this region and similar climate conditions are recommended.