Molecular Soil Biology 2025, Vol.16, No.6, 325-334 http://bioscipublisher.com/index.php/msb 330 Figure 1 Effects of controlled-release nitrogen on yield and nitrogen use efficiency (Adapted from Hu et al., 2023) 5 Interactive Effects of Irrigation and Fertilization 5.1 Synergistic effects of water and nutrient supply Different irrigation intervals (70, 100, 130, and 160 mm evaporation) together with different fertilizer treatments had a strong influence on leaf N and P content and grain yield. When irrigation was delayed from 70 mm to 160 mm, both nutrient content in leaves and grain yield gradually went down. Even so, applying fertilizer still increased leaf N and P content under all irrigation conditions. Under serious water shortage (160 mm), the mixed fertilizer treatment, which included chemical fertilizer, vermicompost, and PGPR, performed the best and gave the highest leaf N and P content. When water supply was normal, chemical fertilizer alone (around 300 kg N + 150 kg P ha-1) produced the highest yield. However, its yield was very close to that of the mixed fertilization treatment, and the difference was not significant. As water stress increased to moderate and severe levels (130 and 160 mm), the mixed fertilization treatment clearly produced more grain than chemical fertilizer, PGPR, or vermicompost used alone (Mamnabi et al., 2020). In another study, three irrigation levels (60%, 80%, and 100% CPE) were combined with three fertilizer rates (60%, 80%, and 100% of the recommended amount). The results showed that drip irrigation at 80% CPE, together with 80%~100% of the recommended fertilizer rate, could achieve nearly the same grain yield as full irrigation and full fertilization. At the same time, this treatment showed the best irrigation use efficiency and water use efficiency. Compared with the traditional practice of flood irrigation with soil-applied fertilizer, this method saved about 35.4% of water and increased grain yield by 18% (Kumar et al., 2021). 5.2 Constraining effects of water-nutrient imbalance Under conventional tillage, nitrate leaching was very high when normal irrigation was used together with urea. The average value was 83.1 kg/ha. When water supply was reduced and no fertilizer was applied, nitrate leaching dropped sharply. In this case, the value was only 10.4 kg/ha. Compared with urea alone, vermicompost clearly helped reduce nitrate loss. The reduction ranged from 49% to 67%. When urea and vermicompost were used together (VU), nitrate leaching was also lower, with a reduction of about 34%~50%. Across all irrigation levels and tillage methods, the VU treatment performed best overall. Grain yield was the highest under this treatment. Oil content and nitrogen use efficiency (NUE) also reached their highest levels (Khodabin et al., 2022). Another study was carried out in the semi-arid Qazvin region. This experiment combined three irrigation levels (FC60, FC80, and FC100) with different rates of farmyard manure (0, 15, and 30 t FYM ha-1). Under severe water stress (FC60), plant performance clearly declined. Chlorophyll content, branch number, and pod number all
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