Effects of different potassium fertilization rates on root-soil interaction in Korla fragrant pear orchards

To clarify the responses of the soil-root system in Korla fragrant pear orchards to different potassium application rates and their relationships with yield formation, this study evaluated the effects of potassium fertilization across the vertical soil profile, with the aim of providing a basis for rational potassium management in drip-irrigated Korla fragrant pear orchards.

A field experiment was conducted in a 7-8-year-old Korla fragrant pear orchard under drip irrigation. Four potassium treatments were established: K0 (0 kg hm^-2), K1 (75 kg hm^-2), K2 (150 kg hm^-2), and K3 (225 kg hm^-2). Soil physicochemical properties, soil enzyme activities, root vitality, and fruit yield were measured at depths of 0-20, 20-40, and 40-60 cm. Mantel tests, principal component analysis (PCA), and partial least squares structural equation modeling (PLS-SEM) were used to analyze relationships among the measured variables.

Potassium application generally improved soil nutrient availability and the activities of several soil enzymes while reducing soil pH and electrical conductivity (EC), although the magnitude of these responses varied with potassium application rate and soil depth. Potassium application significantly increased root vitality and was accompanied by adjustments in root anatomical traits, including cortical thickness, vascular tissue cell composition, vessel area, and root cross-sectional area. Most soil, enzyme activity, and root-related indicators showed favorable responses under the K2 treatment, and fruit yield under K2 was 47.36% higher than that under K0. PCA and PLS-SEM indicated strong associations among soil physicochemical properties, enzyme activities, root traits, and fruit yield.

Under the soil conditions, tree age, and drip-irrigation management regime of this study, the 150 kg hm^-2 potassium treatment showed favorable integrated soil-root responses and yield performance. However, its broader suitability requires further validation through multi-year and multi-site experiments.