The effect of different forms and concentrations of zinc application on seed yield and oil quality of rapeseed under drought conditions

drought stress is the most important abiotic stress that limits the growth and development of agricultural plants. Zinc is one of the required elements for plant chemical processes, and its application in water shortage conditions can improve the effects of drought stress. Studies have shown that the application of zinc fertilizer to reduce the negative effects of drought stress leads to an increase in yield and yield components of agricultural plants. Therefore, this study was conducted in order to evaluate the application of different forms and concentrations of zinc fertilizer on the yield and oil quality of Neptune variety rapeseed oil under water stress conditions during the years 2019 and 2020 in Biston region located in Kermanshah province.

The experiment was carried out in the form of a split-plot design based on a randomized complete block design in four replications. Water stress treatment as the main factor (no stress, interruption of irrigation at the beginning of flowering and interruption of irrigation at the beginning of the formation of khorjin), foliar treatment as a secondary factor at two levels (spraying zinc sulfate solution and foliar spraying zinc nanochelate) with three concentrations of zero, 3 and 5 per thousand. After collecting the test data, they were analyzed using SAS software.

The results showed that the effect of drought stress and application of zinc sulfate on the characteristics of seed yield, biological yield, seed oil percentage, seed oil yield, erucic acid percentage and oleic acid percentage were significant. Also, according to the results of the comparison of the average test data, it was found that increasing the concentration of zinc sulfate and nano zinc application increased the grain yield and biomass up to 2839 kg/ha and 14634 kg/ha, respectively. The effect of zinc nanochelate on the increase of these two traits was greater than that of zinc sulfate. Oil percentage and yield decreased in both levels of water stress. According to the results, it was found that increasing the concentration of zinc and especially the nano form increased the percentage up to 43.6% and the yield of seed oil up to 1423 kg per hectare. In addition, it was found that water stress reduced the percentage of oleic acid in rapeseed oil, but nanozinc foliar application partially compensated for this decrease and increased the percentage of oleic acid to 65.75%.

According to these results, it was found that although the percentage of oleic acid decreased with the interruption of irrigation during the flowering and podding stages, the results showed that the application of zinc nanochelate in the conditions of drought stress and the absence of drought stress had a more positive effect on increasing the percentage of oil oleic acid. Therefore, the application of nano zinc chelate can be suggested in the conditions of drought stress to increase the yield and quality of rapeseed oil in the region. As a result, in order to achieve the maximum seed yield and high oil quality in rapeseed, a concentration of 5 per thousand zinc nanochelates can be used in the absence of drought stress.