Molecular Soil Biology 2025, Vol.16, No.6, 325-334 http://bioscipublisher.com/index.php/msb 331 decreased, and adding farmyard manure did not change this trend. Under moderate deficit irrigation (FC80), the situation was different. Applying 30 t FYM ha-1 significantly increased pod number and yield in the Hydromel variety. The yield under this treatment was close to that of full irrigation with manure (FC100 + FYM30). At the same time, about 20% of irrigation water was saved (Janmohammadi et al., 2024). 6 Implications for Rapeseed Production Practice 6.1 Irrigation quota and scheduling recommendations Using only rainfall was not the best option. When extra irrigation was added at different stages, including the vegetative stage, flowering stage, and early grain filling stage, crop yield increased clearly. Among all treatments, irrigating when about 50% of the available soil water in the root zone was used up at the start of flowering gave the best result. This method balanced water use efficiency and economic benefit well. In an experiment using ridge–furrow full-film mulching in the arid areas of Northwest China, clear differences were observed. Without any irrigation, the RFFM0 treatment still greatly increased root and shoot biomass, as well as nutrient uptake. Compared with flat planting without irrigation (FP0) and flat planting with only 30 mm of winter irrigation (FP1), yield increased by 23.7–39.0%. Water use efficiency also rose by 71.3%~86.5%. In normal and wet years, the yield under RFFM0 was close to that of FP3, which included three irrigations totaling 150 mm (Gu et al., 2019). 6.2 Fertilization Strategies under Different Water Scenarios Under normal or nearly full irrigation conditions, a high rate of chemical nitrogen fertilizer (around 300 kg N ha-1) produced the highest grain yield of spring rapeseed in the Tabriz experiment. This result was observed under conventional irrigation management. However, the yield was very close to that of the integrated fertilization treatment, which included 1/3 chemical fertilizer, 1/3 vermicompost, and PGPR. The difference between these two treatments was not significant (Mamnabi et al., 2020). Under water-limited conditions, including moderate and severe water deficit levels (130 and 160 mm supplemental irrigation), the integrated fertilization treatment showed better performance than using only chemical fertilizer or only organic fertilizer. Even with about a 67% reduction in chemical fertilizer input, this combined approach still increased leaf nitrogen and phosphorus contents. At the same time, grain yield was also significantly improved under drought conditions (Nasrollahzadeh et al., 2023). 6.3 Relevance to sustainable and climate-resilient agriculture In the Karaj experiment, nitrate leaching changed a lot under different fertilizer and water treatments. When conventional tillage was used, irrigation was normal, and urea was applied only once, nitrate loss was relatively high. The average leaching amount was 83.1 kg/ha. This showed that nitrogen was easily lost under this management practice. When irrigation conditions stayed the same, part of the urea was replaced with vermicompost. After this adjustment, nitrate leaching was clearly reduced. The loss amount was only about half of that under full urea application. At the same time, crop performance did not decline. Grain yield and oil yield remained stable. Nitrogen use efficiency also improved to some extent (Khodabin et al., 2022). Model simulations over a long time period indicate that similar issues may occur in central China, where rainfall is relatively high. In these regions, nitrogen fertilizer input should be properly controlled. The recommended long-term application rate ranges from 120 to 160 kg N ha-1. Applying nitrogen within this range can help avoid excessive input and reduce nitrogen loss. In addition, field management practices also play an important role. Planting density and sowing time can be adjusted based on local soil properties and weather conditions. These adjustments help stabilize crop yield and economic benefits. They also lower environmental risks and contribute to long-term food security (Wang et al., 2022).. 7 Challenges, Limitations, and Future Perspectives 7.1 Regional differences and production constraints In the semi-arid regions of Iran, FC80 combined with 30 t/ha of farmyard manure can maintain high Hydromel yields while saving 20% of water, while FC60 was proven to be "stress-induced deficit irrigation" and is not recommended in the area (Janmohammadi et al., 2024). Annual fluctuations in rapeseed yield in China have been confirmed to be highly dependent on socioeconomic factors such as effective irrigated area, total fertilizer application, and agricultural machinery power, with up to 89% of the variation in winter rapeseed yield being explained by economic variables.
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