Excessive Potassium Fertilization Reduces Sugar Distribution in Taproots and Sugar Yield in Drip-Irrigated Sugar Beets Cultivated in Calcareous Soils
摘要
Potassium is vital for sugar crop growth, yet excessive application often limits yield and quality improvements in sugar beets. To determine the optimal type and application rate of potassium fertilizer for drip-irrigated sugar beets in lime soils, a field experiment was conducted in 2024. Two cultivars (KWS9899 and KWS7748) were treated with two potassium sources (KCl and K2S04) at four application rates (K2O) [0 (CK), 105, 210, and 315 kg/ha]. We evaluated their effects on taproot yield, sugar content (total soluble sugar, sucrose, fructose, glucose), and K+ content in the shoots and taproots. Results revealed that taproot yield and sugar production increased initially but declined with further potassium application, maximum at 210 kg/ha. Compared with the non-fertilized control, potassium application increased taproot yield by 17.42–72.08% and sugar production by 19.48–98.74%, with potassium sulfate at 210 kg/ha achieving the highest yield values. Additionally, potassium fertilization enhanced total soluble sugar and sucrose content in taproots by 1.72–6.68% and 16.00–54.02%, respectively. Notably, the highest sugar content in shoots was observed at 315 kg/ha, suggesting excessive potassium impedes sugar translocation to taproots. The 210 kg/ha rate also resulted in the highest potassium use efficiency, with potassium sulfate being more effective than potassium chloride. In conclusion, applying potassium sulfate at 210 kg/ha is most effective for enhancing sugar partitioning to taproots and improving yield and sugar productivity in drip-irrigated sugar beets under lime soil conditions.