Bioscience Evidence 2024, Vol.14, No.6, 270-280 http://bioscipublisher.com/index.php/be 273 been shown to produce more grain per unit of water applied, with water productivity reaching 6.3 kg ha-mm-1 compared to 3.3 kg ha-mm-1 under conventional management practices (Thakur et al., 2018). Controlled irrigation, another water-saving technique, has been found to reduce water input by 17% while maintaining high rice yields and nitrogen use efficiency (NUE) (Cao et al., 2020). Additionally, integrating water management with optimized nitrogen application can further enhance WUE and reduce environmental impacts. For instance, coupling AWD with appropriate nitrogen management has been shown to improve NUE and reduce nitrogen loss (Sun et al., 2012; Qiu et al., 2022). Figure 2 Planting mode for drip irrigation under plastic film mulching (Adopted from Zhao et al., 2023) 4.3 Effects of water stress on yield Water stress can have significant adverse effects on rice yield, but certain agronomic practices can mitigate these effects. Higher nitrogen fertilization has been shown to alleviate the negative impacts of water stress on lowland rice, resulting in increased growth, water status, and yield under deficit irrigation conditions (Abdou et al., 2021). However, severe water stress, such as that experienced under dry cultivation, can lead to substantial yield reductions. For example, dry cultivation has been associated with an average 21.25% reduction in rice yield (Qiu et al., 2022). On the other hand, moderate water stress, managed through techniques like AWD, can maintain or even improve yield while conserving water. Studies have shown that AWD can maintain similar grain yields to CF while saving significant amounts of water (Atwill et al., 2018; Santiago-Arenas et al., 2021). Additionally, optimizing water and nitrogen management under drip irrigation has been shown to improve photosynthetic performance and nitrogen metabolism, leading to higher yields even under limited water conditions (Zhao et al., 2023). 5 Planting and Crop Management Practices 5.1 High-yield planting density and spacing High-yield planting density and spacing are critical factors in rice cultivation that significantly influence crop productivity. The System of Rice Intensification (SRI) has demonstrated that wider spacing, such as 20 × 20 cm, can enhance root growth, leaf number, tiller and panicle number, and overall grain yield by 40% compared to conventional practices. However, excessively wide spacing, such as 30 × 30 cm, can reduce yield due to lower plant population density (Thakur et al., 2010). In direct-seeded rice (DSR), a higher seeding rate of 50~60 kg ha-1 and narrow row spacing of 15~25 cm have been found to reduce weed biomass by approximately 50% without compromising yield, making it a desirable practice under weedy conditions (Dass et al., 2016). 5.2 Seed selection and sowing techniques Seed selection and sowing techniques are pivotal in achieving high rice yields. The choice of cultivar, seedling vigor, and early establishment are essential for competitive growth against weeds and pests (Dass et al., 2016). In the Mediterranean region, late sowing under organic management has been shown to increase initial plant density, enhancing competition with weeds and ensuring sufficient panicle numbers at harvest (Delmotte et al., 2011). Additionally, innovative sowing techniques such as dry direct seeding and water seeding have emerged as labor-saving and water-efficient alternatives to traditional transplanting, although they require effective weed management to prevent yield losses (Jehangir et al., 2021).
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