Effects of potassium fertilization on cold resistance in Korla fragrant pear

• Potassium at 150 kg/ha enhanced SOD, POD, CAT, and proline, improving cold resistance. • N, P, K, Fe, Mn, and Cu increased under K150 and correlated with frost-tolerance traits. • K150 reduced MDA and relative conductivity and increased fruit yield by 47.36 %. This study aimed to evaluate the effect of potassium fertilizer on the cold resistance of Korla fragrant pear trees and to determine the optimal application rate. A field experiment was conducted on 7–8-year-old pear trees under drip irrigation, using four potassium fertilization treatments: K0 (0 kg/hm 2 ), K75 (75 kg/hm 2 ), K150 (150 kg/hm 2 ), and K225 (225 kg/hm 2 ). Cold resistance indices of current-year shoots and perennial branches were assessed across different growth stages. Correlation analyses were performed among potassium application rates, mineral nutrient contents, and cold resistance indices. Compared with the control (K0), the low-rate treatment (K75) had no significant effect on cold resistance indices but significantly increased Ca and Mg contents in branches. The medium-rate treatment (K150) significantly enhanced the contents of N, P, K, Fe, Mn, and Cu, increased proline concentration, and promoted the activities of SOD, POD, and CAT enzymes. MDA content and relative conductivity were significantly reduced, and fruit yield was notably improved. In contrast, the high-rate treatment (K225) inhibited Ca and Mg accumulation but also enhanced enzymatic activity (SOD during fruit expansion, POD and CAT during ripening). It also significantly reduced MDA and relative conductivity during fruit expansion, ripening, and dormancy. Significant positive correlations were observed between potassium rates and the concentrations of N, P, K, and Mn, and strong correlations were found between mineral nutrients, cold resistance, and yield. An application rate of 150 kg/hm 2 potassium under drip irrigation was found to be optimal, significantly enhancing cold resistance, improving mineral nutrient status, and increasing both tree vitality and yield in Korla fragrant pear production.