Potassium dynamics in orchard soil and potassium status of sour cherry trees affected by soil nutritional conditions

The influence of mineral fertilizers on the seasonal dynamics of exchangeable potassium in the soil, potash status and productivity of trees was studied in field experiment with sour cherry trees cv. ‘Turgenevka’ in soil-climatic condition of Central Russian upland in 2018-2019. The urea and potassium sulfate were applied annually in early spring at doses of N30K40, N60K80, N90K120, and N120K160 kg/ha. The potassium level in soil-plant system depended on weather conditions, the doses of fertilizers and uptake of the element by trees. The reserves of exchangeable potassium in loamy Haplic Luvisol at the level of 100-200 mg/kg were sufficient to ensure the sour cherry yield in the start of fruiting. Fertilization by doses of N60K80 and higher increased the content of exchangeable potassium in root zone (more than 200 mg/kg), but the features of potassium seasonal dynamics were similar to unfertilized plots. With increase in the average fruit load from 4.6 (2018) to 8.3 (2019) kg/tree, the uptake of potassium by young trees increased, which led to a significant decrease in the concentration of potassium in the soil and leaves during the fruit development period (June and July). Fertilization reduced this effect but did not significantly influence on the productivity of trees and fruit potassium status