Effects of Potassium Fertilizer Base/Topdressing Ratio on Dry Matter Quality, Photosynthetic Fluorescence Characteristics and Carbon and Nitrogen Metabolism of Potato

Potassium is an essential nutrient element for potato production. However, there is little research on how the base/topdressing ratio of potassium fertilizer affects plant growth. Therefore, in this 2-year (2022–2023) study, we used Longshu 7 as the experimental material and conducted a pot experiment. Under the condition of total potassium application of 5.4 g/plant, the potassium fertilizer base/topdressing ratios were as follows: CK (10:0), T1 (2:8), T2 (4:6), T3 (6:4), and T4 (8:2). We investigated the effects of potassium fertilizer application on dry matter quality, endogenous hormones, photosynthetic fluorescence characteristics, carbon and nitrogen metabolism and yield in potato. The results of the study demonstrated that potassium topdressing had a positive effect on plant growth through the optimization of endogenous hormone content and regulation of cell elongation. In addition, potassium application can enhance the activity of enzymes related to carbon and nitrogen metabolism, promote photosynthesis, improve the transport efficiency of photosynthetic products and enhance the dry matter quality of tubers. Among all the potassium topdressing treatments, the T2 treatment exhibited a significant difference. However, it is important to note that an excessive increase in the base/topdressing ratio of potassium fertilizer may have detrimental effects on the levels of gibberellin A3 (GA₃) and starch content. Based on Pearson correlation analysis, it was determined that the activities of sucrose synthase (SuSy), sucrose phosphate synthase (SPS) and glutamine synthetase (GS) play a significant role in influencing the dry matter quality of potato tubers. These findings provide valuable insights into the importance of these factors in potato production. Overall, the results of this study highlight the significance of maintaining an appropriate ratio of base to topdressing of potassium fertilizer. This optimal ratio ensures the efficient assimilation and utilization of nitrogen and carbon, ultimately serving as a valuable theoretical foundation for effective potassium fertilizer application in potato production.