Molecular Soil Biology 2025, Vol.16, No.4, 175-187 http://bioscipublisher.com/index.php/msb 1 79 4.3 Influence of planting depth on yield The performance of sweet potato seedlings is significantly affected by the transplantation posture, which is determined by the planting depth. Therefore planting depth is another critical factor influencing sweet potato yield. Independently refined by Jinhua Academy of Agricultural Sciences, this automated sweet potato transplanter adapts to local pedo-geomorphic conditions while enhancing planting efficiency and yield. Furthermore, its precision technology regulates planting depth and seedling orientation, supplements optimal moisture, adjusts ridge height, and compacts the ridge surface. These functions ensure all seedlings attain ideal planting depth, contributing to uniform transplanting quality across heterogeneous soils and elevated survival rates (typically >95% in field trials) (Figure 2). Figure 2 Simplified mechanical diagram of automated sweet potato transplanter. 1-main control device; 2-power transmission device; 3-water supply device; 4-transplanting device; 5-compacting device; 6-refill device; 7-furrow device; 8-ridging device; 9-Rotary tillage device Optimizing the structure of transplanting equipment, such as the self-covering soil opener, can improve the quality of transplanting by ensuring the correct planting depth and posture (Wu et al., 2023). Field experiments have shown that different transplanting configurations, such as the use of finger-clip type transplanters on mulched raised beds, can lead to higher yields by maintaining optimal planting depth and soil temperature (Li et al., 2023). Additionally, flat planting has been found to produce higher yields compared to ridge planting under certain soil conditions (Pepó, 2018; 2020). 5 Irrigation and Water Management 5.1 Water requirements at different growth stages Sweet potatoes are generally considered drought-tolerant plants, but they still require a consistent supply of water to thrive. Sweet potatoes have different water requirements at various growth stages, which significantly influence their growth and yield. At the vine growth stage, regular watering is essential to support vigorous growth. During the late-season growth phase, moderate irrigation (75% of crop evapotranspiration, ETc) has been shown to enhance the source-sink balance, increase photosynthetic rates, and promote the allocation of photosynthates to storage roots, thereby improving yield and water use efficiency (WUE) (Zhou et al., 2023). Excessive or insufficient irrigation during this period can negatively impact the transfer and allocation of photosynthetic products, leading to suboptimal yields. 5.2 Efficient irrigation methods for sweet potatoes Efficient irrigation methods are crucial for optimizing sweet potato yield and water productivity. Drip irrigation, particularly when combined with bed planting, has been found to be superior in terms of water saving and productivity compared to traditional furrow irrigation methods (Waqas et al., 2020). Drip irrigation allows for precise water application, reducing water wastage and enhancing water use efficiency. Additionally, regulated deficit irrigation (RDI) strategies, where water supply is reduced during less critical growth stages, can maintain high yields while conserving water. For instance, applying mild water deficits during the seedling stage can result in high yields and improved water use efficiency (Li et al., 2021).
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