Changing of the fractional composition of phosphates at long-term application of fertilizers
The effect of prolonged use of fertilizers and liming materials on the fractional composition of phosphates of light gray forest soils under long-term field experiment is studied. In a steady-state field experiment (1964-2013) introduction of phosphate fertilizers increased the total content of the element in a light gray forest soil in relation to the unfertilized control. Organo-mineral fertilizers and liming system helped to increase the share of organic forms of phosphorus. Fractional composition analysis showed that the proportion of loosely bound phosphates of soil is less than 1%, the highest proportion of non-retrievable (28-38 %) and Fe- P (33-34 %). The greatest number of iron phosphate noted in the joint application of mineral and organic fertilizers at non-limed background, the lowest - in the control variant at liming. Liming provided a significant increase in the fraction of Ca - P and a reduction in non-retrievable phosphates. Most dynamic groups are loosely bound phosphate (V = 11-25%) and alumo-phosphates (V = 5-26%), liming, in most cases, contributes to reduce the variability of the analyzed parameters.
Keywords: perennial field experiment, fertilizer system, liming, phosphate regime of the soil, fractional composition of phosphates