Molecular Soil Biology 2025, Vol.16, No.6, 325-334 http://bioscipublisher.com/index.php/msb 328 use efficiency reached 71.6 kg/(ha·mm). The total water use efficiency was 7.7 kg/(ha·mm). This result shows that limited irrigation can still be effective at this stage (Istanbulluoğlu et al., 2010). In Southwest China, a two-year rainfed rotation with seasonal drought was tested. In drought years, using only one water management method, such as ridge–furrow rainwater collection or straw mulching, did not greatly increase yield. However, when these methods were combined with reduced-rate slow-release fertilizer (RF+SR or SM+SR), the results improved. Yield increased by 7.7%~29.9%, and water use efficiency increased by 14.8%~28.7% in both dry and wet years. At the same time, total water use during the growing season was lower than that of local traditional farming practices (Feng et al., 2020). In a semi-arid area of Qazvin, a three-level irrigation experiment was carried out. When soil moisture was kept at 80% of field capacity (FC80), the yield of the Hydromel variety was only slightly lower than at full irrigation (FC100). However, this treatment saved about 20% of irrigation water. Based on these results, the authors suggested that FC80 combined with 30 t/ha of farmyard manure is suitable for water-saving rapeseed production in this region. In contrast, 60% field capacity (FC60) was considered too low, as it greatly reduced pod number and seed yield (Janmohammadi et al., 2024). 4 Effects of Fertilization Regimes on Rapeseed Yield 4.1 Nitrogen management and yield response At three nitrogen fertilizer levels (0, 180, and 240 kg N ha-1), nitrogen application significantly increased nitrogen accumulation in rapeseed plants during flowering, the number of pods per plant, the number of branches, and the number of seeds per pod, and showed a significant positive correlation with grain yield. The 180 kg N ha-1 treatment showed the best overall performance in terms of grain yield and nitrogen use efficiency. When the nitrogen application rate increased from 180 to 240 kg/ha, the yield only increased slightly or not significantly, while nitrogen partial productivity (PPN) and nitrogen use efficiency (NUE) showed a downward trend. Leaf nitrate reductase (NR) and glutamine synthetase (GS) activities peaked at 180 kg N ha-1, and increasing nitrogen levels did not increase the activity of key nitrogen metabolic enzymes (Wang et al., 2025). In continuous ridge-tillage and mulching cultivation in the arid region of Northwest China, with six nitrogen levels from 0 to 300 kg N ha-1, dry matter, nitrogen uptake, grain yield, and oil content were significantly higher at N180, N240, and N300 compared to N0~N120. However, WUE and N recovery efficiency did not differ significantly between N180 and N240, and both were significantly higher than N300; however, N240 had an average grain yield 11.9% higher than N180 (+427 kg/ha), making it the optimal nitrogen application rate (Gu et al., 2017). In a side-row mulching cultivation experiment under different soil fertility conditions, with nitrogen application rates of 0~360 kg/ha, low-fertility plots (F1, F2) required ≥360 or approximately 300 kg N ha-1 to achieve the highest yield, while high-fertility plots (F3, F4) reached peak yields at 272–312 kg N ha-1, with corresponding yields 15.8%~242.3% higher than those with lower nitrogen treatments (Tian et al., 2023). 4.2 Balanced N, P, and K fertilization and yield-increasing effects In a long-term experiment conducted at three sites over two cropping years in the rice-oilseed rape rotation system in Central China, comparisons of four mineral fertilizer treatments (NPK, NP, NK, and PK) showed that the total oilseed rape yield (two-year total) under the NPK treatment was 827~4 287 kg/ha, significantly higher than that under NP, NK, and PK treatments. Compared to the PK treatment, oilseed rape yield increased by 61%~76%, and rice yield increased by 19%~41%. Nitrogen deficiency was the primary limiting factor, followed by phosphorus and potassium. N, P, and K uptake were highest in the NPK treatment and lowest in the PK treatment, and all NP, NK, and PK treatments significantly reduced the soil's inherent nutrient supply capacity (INuS) (Yousaf et al., 2017). In a split-plot experiment in Zanjan, Iran, with a full factorial combination of N (0, 100, 200 kg ha-1) and P (0, 75, 150 kg/ha), the combined application of 200 kg N ha-1 and 75 kg P ha-1 significantly increased chlorophyll content and photosystem II quantum efficiency, increased stomatal conductance after flowering, and prolonged the grain filling period; however, single application of 200 kg N or its combination with higher P levels did not show significant gains for most traits, and oil content even decreased (Zangani et al., 2021). In a combination of four nitrogen application levels (0~270 kg/ha) × four potassium application levels (0~180 kg K2O ha-1), the combined application of N and K was a prerequisite for high yield. Compared to no N and K
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