PHOSPHATE REGIME OF BROWN FOREST ACIDIC SOILS DURING THE EXPLOITATION OF TEA PLANTATIONS WITH DIFFERENT RATES OF APPLIED FERTILIZERS IN THE SUBTROPICS OF RUSSIA

Abstract

The dynamics of phosphorus supply of brown forest acidic soils in the humid subtropics of Russia under conditions of a long-term field experiments with 16 NPK-fertilizers combinations on tea culture was studied for 27 years. The trend of the changes (degree and speed) is represented graphically, by regression and correlation dependencies, approximating functions. A dose of phosphorus fertilizers of 60 kg/ha, with long-term systematic application in combination with the suffi cient doses of NK-fertilizers, provided a content of mobile phosphate in soil at an average level of 40- 60 mg/100 g (optimal) and a non-deficit phosphorus balance in the agrosystem. The application of 120-180 kg/ha of phosphorus fertilizers led to a 2-3 fold increase in the content of mobile phosphates (in the 0-20 cm soil layer), with an average rate of 30-40 mg/100 g for 10 years or 25-30 mg/100 g per ton of applied P fertilizers. “Overphosphating” of soils was expressed by proportional growth of total phosphorus. In the absence of phosphorus fertilizers, the high yield of tea was provided by the created pre-plant phosphorus reserve (with some depletion), effective in aftereffect.