Molecular Soil Biology 2025, Vol.16, No.4, 175-187 http://bioscipublisher.com/index.php/msb 1 78 3.2 Soil preparation techniques for enhanced yield Proper soil preparation is fundamental to achieving high yields in sweet potato cultivation. This process begins with thorough land preparation, which is essential for creating an optimal environment for sweet potato growth. The establishment of well-structured planting beds is recommended to ensure proper drainage and aeration, both of which are vital for root development. To cultivate robust seedlings, the application of base fertilizers, particularly phosphorus and potassium, plays a critical role in soil preparation.These nutrients are essential for the development of a strong root system and overall plant vigor (Fan et al., 2018). In sandy soils, the application of phosphorus at appropriate levels can significantly boost tuber yield and starch concentration, particularly in areas with low initial soil phosphorus levels (Cordeiro et al., 2023). Furthermore, integrating organic amendments, such as compost and green manure, into the soil can substantially improve both soil structure and fertility. These amendments not only enrich the soil with essential nutrients but also enhance its organic matter content, which in turn improves water retention, soil aggregation, and microbial activity (Larkin et al., 2021; Agbede and Oyewumi, 2022). Collectively, these factors contribute to enhanced crop growth and higher yield. 3.3 Nutrient management and soil health maintenance Nutrient management is a critical component of soil health maintenance and sweet potato productivity. Sweet potatoes have a high demand for nutrients, particularly nitrogen, phosphorus, and potassium. The combined application of biofertilizers and inorganic nutrients has been demonstrated to significantly enhance sweet potato yields. For instance, the use of arbuscular mycorrhizal fungi (AMF) in combination with nitrogen and potassium fertilizers can significantly increase both tuber yield and overall biomass (Mukhongo et al., 2017). Additionally, the incorporation of green manure crops, such as Mucuna aterrima, enriches soil nutrients and promotes sweet potato growth, thereby reducing the need for high doses of mineral nitrogen fertilizers (Fernandes et al., 2020). This approach not only optimizes nutrient uptake but also contributes to a more sustainable and efficient agricultural system. 4 Planting Techniques 4.1 Optimal planting time and density Optimal planting time and density are indeed crucial for maximizing sweet potato yields, and recent research has provided valuable insights into these agronomic practices. An appropriate planting density can balance shoot and root development, promoting storage root formation and increasing storage root number (Shao et al., 2018; Liang et al., 2023). Research on the 'Longshu 13' variety revealed that early planting, combined with a density of 49 995 plants per hectare, resulted in higher yields (Zi-lon, 2015), highlighting the importance of both timing and density. Similarly, the 'Wanshu 34' variety achieved high yields when planted in the last ten days of May with a density of 4 500~5 000 plants per 667 m2 (Wenhui et al., 2006). Experiments conducted using “Hungary” demonstrated that a row spacing of 0.75 meters was more favorable than 1.0 meters, leading to higher marketable tuber yields (Pepó, 2018; 2020). These indicate that row spacing is another critical factor in optimizing land use and improving yields of sweet potato. 4.2 Use of cuttings vs. seed propagation The method of propagation, whether through vine cuttings or seed propagation, also affects sweet potato yield. The most common method for propagating sweet potatoes is through the use of vine cuttings. This involves taking 25~30 centimeter-long cuttings from healthy, insect- and disease-free plants (Essilfie et al., 2016). Studies have shown that using vine cuttings, particularly the top vines, can significantly enhance yield (Zi-lon, 2015; Sarkodie-addo et al., 2017). In some colder climates where vines do not develop well, farmers may plant storage roots, which could be considered a form of seed propagation. This method requires cultivar with strong early vigor to compete with weeds effectively. Genotypes like 'Kyushu No.198' have shown promising results in terms of early vigor and shoot dry matter yield (Sakaigaichi et al., 2020). However, the use of secondary transplants from shoots has been found to yield higher results on ridges compared to primary transplants from tubers (Szarvas et al., 2018).
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