Bioscience Methods 2026, Vol.17, No.1, 43-56 http://bioscipublisher.com/index.php/bm 49 (Liu et al., 2022). Secondly, potassium affects the transport and distribution of assimilates. When potassium nutrition is good, the vascular tissues of the plant are developed and the osmotic potential gradient is large, facilitating the timely output of photosynthetic products from leaves and their transportation through the stem to the tubers (Jiang et al., 2024). Studies have shown that applying potassium fertilizer at the base can reduce the excessive accumulation of starch in leaves during the early growth stage, while increasing the sucrose concentration and sucrose/starch ratio in leaves in the middle and late stages, enhancing the ability of leaves to transport assimilates (Gao et al., 2021). Moreover, applying potassium can thicken the stems, increase the cross-sectional area of transport channels, and enhance the potassium concentration gradient within the stems, improving the efficiency of photosynthetic product transportation from both physical and chemical perspectives (Jiang et al., 2024). These effects enable more photosynthetic products to be smoothly transported to the tubers. Finally, potassium affects the strength of the tuber "storage". A strong storage means that the tuber has a greater capacity to accommodate and assimilate assimilates. Potassium fertilizer promotes the expansion and division of tuber cells, increases the absorption rate of assimilates by tuber tissues, and activates enzymes related to starch synthesis in the tubers, enabling the sucrose transported to the tubers to be converted into starch for storage more quickly (Gao et al., 2021). For example, applying potassium can reduce excessive starch synthesis in leaves in the early stage, ensuring more sucrose is transported as a mobile form to the tubers; at the same time, accelerating the unloading and assimilation of sucrose in the tubers, allowing the tubers to rapidly expand and accumulate dry matter (Gao et al., 2021). In summary, potassium fertilizer enhances photosynthetic source supply, promotes catabolic transport, and increases tuber storage capacity, synergistically promoting the formation and accumulation of dry matter in sweet potato tubers. This physiological process explains why applying an appropriate amount of potassium fertilizer can achieve higher dry matter yield and starch deposition. 5.3 Trade-off between dry matter rate and yield, quality, and determination of the optimal range In sweet potato production, there is a certain trade-off relationship between the dry matter rate of the tubers and the yield and quality indicators of the fresh tubers. It is necessary to find the balance point for optimization (Geng et al., 2024). On one hand, an excessively high dry matter rate often indicates a high starch content and low water content in the tubers, which usually occurs in small tubers with limited growth. Practice shows that under extreme potassium deficiency or water shortage conditions, although the sweet potato tubers are small in size, the dry matter concentration may be relatively high (Sheng et al., 2023). However, at this time, the total yield is very low and the texture is dry, which is not conducive to the fresh food quality. On the other hand, pursuing an excessively high yield of fresh tubers sometimes leads to a decrease in the dry matter rate of the tubers (Singh et al., 2017). In experiments with a large amount of potassium chloride fertilizer, it was observed that as the yield increased, the water content of the tubers significantly increased, and the dry matter rate decreased instead (Huang et al., 2025). This interplay between yield and dry matter rate makes maximizing a single indicator not the best strategy. In actual production, a compromise needs to be reached between the two: both a high yield and an appropriate dry matter content in the tubers are needed to ensure flavor and processing quality. Therefore, this study determined an optimal range for potassium fertilizer application through multi-objective analysis, within which the yield and dry matter rate of sweet potatoes can be maintained at a high level simultaneously (Geng et al., 2024). Specifically, under this optimal potassium application range, the fresh weight yield of sweet potato tubers is close to the maximum and the rate of commercial tubers is high, while the dry matter rate is at a moderate and slightly elevated level (neither too low to affect quality nor too high to reduce palatability). It is worth noting that the influence of different potassium fertilizer forms on the dry matter rate also needs to be considered: using sulfate potassium is beneficial for maintaining a high dry matter content while increasing yield; while potassium chloride may slightly reduce the dry matter rate while increasing yield (Huang et al., 2025). At this time, appropriate control of the dosage should be used to avoid going too far. Through the above trade-off analysis and experimental data, this study determined the optimal potassium application range that can balance the yield and dry matter (starch) content of sweet potatoes, providing a scientific basis for formulating fertilization schemes in production that both ensure yield and quality.
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