پژوهشهای زراعی ایران (Mar 2024)
Evaluation of Rapeseed Production and Water Use Efficiency in Irrigation Regimes and Vermicompost Levels in Different Planting Dates
Abstract
IntroductionRapeseed is the second most important plant for oil production in the country due to having more than 40% of oil in the seed, resistance to some environmental stresses, and suitable combination of fatty acids. Water deficit in the stage of reproductive growth severely affects the rapeseed yield because the number of seeds and the weight of seeds decrease. Water shortage in the flowering stage also reduces the seed oil percentage and oil yield of rapeseed. In some areas of Khuzestan province, rapeseed is mainly cultivated as a beak crop. This issue causes the growth period of rapeseed to coincide with the growth of some other crops. In this situation, some irrigation turns are necessarily allocated to other plants (including wheat, which is in the pollination stage, and okra, which is in the germination stage), which causes rapeseed to face water shortage, even in the flowering stage. Therefore, it is necessary to apply appropriate management methods to reduce the effects of drought stress on rapeseed during the flowering stage. Among these methods is the use of vermicompost fertilizer and changing the planting date. The present study aimed to address the following inquiries: What impact does vermicompost fertilizer, planting date, and drought stress during the flowering stage have on rapeseed seed and oil production? Can the utilization of vermicompost fertilizer and adjustments to planting dates mitigate the adverse effects of water deficit stress on rapeseed yield?Materials and MethodsA field experiment was conducted at the research farm of Shadegan Payam Noor University, Khuzestan, Iran in 2022-23 growing season. The experiment was carried out as a three-factor factorial 2x3x2 with three repetitions. The experimental factors included planting date (November 25 and December 25), vermicompost fertilizer (0.0, 10, and 20 ton ha-1), and irrigation (full irrigation and interruption of irrigation during the flowering stage). In each irrigation stage, the volume of irrigation water was measured and to calculate the efficiency of water consumption, the yield (seed and oil) was divided by the amount of evapotranspiration. At the maturity stage, the seed yield and its related traits included the number of pods per plant, the number of seeds per pod, the weight of 1000 seeds, biological yield, harvest index, oil and protein percentage of seed were calculated.Results and DiscussionRapeseed had the highest seed yield (2667 kg ha-1) on the planting date of November 25 with full irrigation, while delay in planting (planting date of November 25) and interruption of irrigation during the flowering stage resulted in the lowest seed yield (1247 kg ha-1) which means a decrease of more than 50% in seed yield. However, if rapeseed is planted on December 25 and fully irrigated, it has a higher seed yield (about 15%) than planting on November 25, along with stopping irrigation during the flowering stage. A similar trend was observed in seed oil percentage and oil yield, so the highest and lowest percentage and yield of rapeseed oil were obtained on the planting date of November 25 with full irrigation and the planting date of December 25 and stopping irrigation at the flowering stage, respectively. The delay in planting and drought stress in the flowering stage reduced the percentage of rapeseed oil by 6% and the yield of oil by about 60%. On the planting date of November 25, rapeseed was superior to the planting date of December 25 in terms of the number of seeds, 1000-seed weight, biological yield, and water efficiency by 35, 25, 23, 18, and 38%, respectively. ConclusionVermicompost fertilizer helped to improve rapeseed seed yield by providing important nutrients. Stopping irrigation during the flowering stage and delaying planting caused a decrease in seed yield and rapeseed oil production. Therefore, to obtain the maximum yield of seed and oil, it is recommended to plant on the 25th of November and full irrigation. It is better to modify the planting pattern in the region to prevent the flowering stages of rapeseed from encountering water shortage.
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