Bioscience Methods 2026, Vol.17, No.1, 43-56 http://bioscipublisher.com/index.php/bm 52 7.2 Case implementation: setting potassium fertilizer application gradient and tracking yield, dry matter rate, and sugar components In the aforementioned low-potassium plots, a potassium fertilizer application gradient experiment was conducted to evaluate the effect of potassium management improvement (Geng et al., 2024). The experiment set multiple potassium application treatments based on a uniform nitrogen and phosphorus fertilizer application, including a no-knowledge control and several increasing levels of potassium fertilizer application (such as K₂O 0, 60, 120, 180 kg/ha, etc.), all using the commonly used potassium fertilizer varieties (sulfate potassium) for application (Singh et al., 2017). To improve potassium fertilizer efficiency and align with the peak period of sweet potato's potassium requirement, this case adopted a staged potassium application strategy: 50% of the total potassium was applied in the base fertilizer stage, and the remaining 50% was applied as a top-dressing at the time of sweet potato mulching (about 50 days after planting, before the rapid expansion of the tubers) (Shu et al., 2024). Throughout the growing season, the growth status and key physiological indicators of each treatment were regularly monitored, and yield and quality indicators were measured when the sweet potatoes were mature and harvested (Gao et al., 2021). Specific observations included: the fresh tuber yield and commercial tuber rate of each treatment; the dry matter rate and starch content of the tubers; the sugar components of the tubers (reducing sugar and sucrose content); as well as physiological parameters such as leaf potassium concentration and photosynthetic rate (Shu et al., 2024). Particularly, sensory evaluation of the sweetness or determination of soluble sugar content was conducted on the tubers before the harvest of the tubers to assess the sweetness quality (Huang et al., 2025). Through these methods, the dynamic effects of different potassium fertilizer inputs on sweet potato yield and tuber quality (especially sweetness) were tracked throughout the process, providing a basis for formulating optimized potassium application measures. 7.3 Case conclusion: identifying the optimal local range and the replicable "stage-based potassium fertilization + goal-oriented" scheme The results of the case trial indicate that increasing the potassium fertilizer application rate significantly improves the yield stability and root quality of sweet potatoes on the low-potassium plots (Geng et al., 2024). Compared with the traditional management without potassium fertilizer application, the treatment with medium-high potassium fertilizer application significantly increases the yield of fresh sweet potatoes, reduces inter-annual fluctuations, and improves the rate of marketable potatoes, demonstrating that the investment in potassium fertilizer has a very significant yield-enhancing effect on low-potassium soil (Singh et al., 2017). At the same time, the content of soluble sugars (especially sucrose) in the roots increases with the increase in potassium fertilizer application rate (Huang et al., 2025). The sweet potatoes treated with an appropriate amount of potassium fertilizer have a significantly better sweetness than the control, and the taste evaluation improves from "plain" to "sweet" (Shu et al., 2024). Comprehensive analysis of yield and quality indicators shows that a medium-high potassium fertilizer application level within this test range achieves the best overall benefits: the yield of fresh sweet potatoes is close to the highest and stable, the dry matter rate of the roots is moderately high, the sucrose content is higher than that of the control, and the flavor and commercial value of the sweet potatoes are simultaneously enhanced (Geng et al., 2024). Further increasing the potassium fertilizer to the highest treatment does not bring significant additional benefits, indicating that there is an optimal range for potassium fertilizer application in local sweet potato production (Singh et al., 2017). Based on this, this case has determined the recommended range of potassium fertilizer application suitable for this plot and summarized a replicable and scalable "Stage-based Potassium Fertilization + Goal-oriented" fertilization scheme: potassium fertilizer is allocated reasonably according to the growth stages, meeting the needs of sweet potato expansion in the middle and later stages while preventing nutrient waste (Shu et al., 2024); and the total amount of potassium fertilizer is adjusted according to the production goals, with a medium-high potassium fertilizer application level selected for marketable sweet potato cultivation to ensure appropriate sweetness, and a higher potassium fertilizer application level selected for starch processing sweet potato cultivation (Figure 1) (Gao et al., 2021). This scheme successfully achieved high yield and high quality of sweet potatoes in the local trial, not only solving the problem of unstable yield and insufficient sweetness in sweet potatoes on low-potassium soil, but also providing a reference example for sweet potato fertilization in similar soil conditions.
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