Abstract
The sowing date is an important factor for expanding the cultivated area of rapeseed and affects seed yield, oil content, and fatty acid compounds. Micronutrient elements play an important role in improving the vegetative and reproductive growth of the plant, especially under conditions of biological and environmental stresses. A two-year experiment (2014-2016) was performed to study the response of rapeseed genotypes to foliar application of micronutrients on different sowing dates. The treatments were arranged as a factorial-split plot in a randomized complete block design with three replicates. Three sowing dates of 7 (well-timed sowing date), 17, and 27 (delayed sowing dates) October and two levels of foliar application with pure water (control), selenium (1.5%), zinc (1.5%), and selenium+zinc (1.5%) were factorial in the main plots and five genotypes of SW102, Ahmadi, GKH2624, GK-Gabriella, and Okapi were randomized in the subplots (a total of 30 treatments). Seed yield, oil yield and content, oleic acid, and linoleic acid were reduced when rapeseeds were cultivated on 17 and 27 October, while the contents in palmitic, linolenic, and erucic acids, and glucosinolate increased (p < 0.01). a selenium+zinc treatment improved seed yield, oil content and yield (p < 0.01). The oil quality increased due to increased contents of oleic and linoleic acids under the selenium+zinc treatment (p < 0.01). The GK-Gabriella and GKH2624 genotypes are recommended to be sown on well-timed (7 October) and delayed sowing dates (17 and 27 October) and treated with selenium+zinc due to the higher oil yield, linoleic and oleic acids.
Highlights
Rapeseed with the scientific name of Brassica napus L. is considered to be one of the most important oilseed plants in the world and it is the third oilseed crop after oil palm and soybean.According to the latest Food and Agriculture Organization (FAO) report, total rapeseed production in the world and Iran were 72.2 and 0.128 million tons, respectively
The results of mean comparison showed that the foliar application of selenium + zinc produced the highest seed yield with an average of 3692 kg·ha-1 and had 17.7, 7.6, and 11.2% higher seed yield compared to the control, selenium, and zinc treatments, respectively (Figure 2)
The selenium+zinc treatment had the highest seed oil yield with an average of 1512 kg·ha-1 and produced 21.8, 12, and 11.2% more seed oil compared to the control, zinc, and selenium treatments, respectively (Figure 2)
Summary
Rapeseed with the scientific name of Brassica napus L. is considered to be one of the most important oilseed plants in the world and it is the third oilseed crop after oil palm and soybean. The sowing date is an important factor for expanding the cultivated area of rapeseed and affects seed yield, oil content, and fatty acid compounds (Koutroubas and Papadoska, 2005). From an agricultural point of view, increasing zinc content in the seeds is a desired qualitative factor and the quantitative and qualitative yields of crops may be reduced under zinc deficiency conditions (Noulas et al, 2018) This element is a factor in reducing the adverse effects of stress on a plant system, and plant growth and metabolism will be affected by any factor affecting its efficiency (Noulas et al, 2018). Regarding the importance of rapeseed as an important oilseed crop, the present study was conducted and aimed to improve the quantitative and qualitative yield of rapeseed genotypes sown on conventional and delayed sowing dates by applying selenium and zinc elements
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