Seasonal dynamics of lead content in sod-podzolic soil in dependence of mineral fertilizer application

Abstract

Influence of prolonged use of increasing doses of mineral fertilizers (NPK by 0-30-60-90-120-150 kg of active matter/ha) on contents and dynamics of acid-soluble and mobile compounds of lead in an arable layer of the sod-podsolic soil was studied during the growing season of 2016. It has been established that prolonged application of fertilizers significantly increases the content of mobile forms of the element in the soil at application of NPK in dozes of 30 and 150 kg of active matter / ha as compared to the control (average values are 0.57, 0.51, and 0.33, respectively). However, even prolonged application of large doses of mineral fertilizers does not lead to a significant increase in lead content in the arable horizons of the soil. Acid-soluble lead compounds range from 2.46 (N0P0K0) to 5.33 mg/kg (N150P150K150); the content of mobile lead compounds from 0.08 to 1.31 mg/kg of soil, respectively, at maximum acceptable concentration of 6.0 mg/kg. The content of acid-soluble and mobile lead compounds in arable horizons of sod-podzolic soil had a reliable dynamics during the growing season on all variants of the experiment. An increase in the content and acid-soluble and mobile compounds is usually observed in the first half of the growing season (end of May - beginning of June), which is probably due to the active mobilization of lead from slow-moving compounds as a result of the activation of microbiological activity under a favorable hydrothermal regime. In the same period, the portion of mobile fractions of lead to acid-soluble fractions increases. Application of increasing doses of fertilizers (30, 60, 90, 120 and 150 kg/ha of active matter) does not always show a reliable increase in the content of the element in the corresponding variant, which is obviously due to the influence of unaccounted factors. A clearer content dynamics is characteristic of mobile lead compounds.