Effect of ammonium sulfate and phosphogypsum application on nutrients dynamics and acidity of black soil

Abstract

The problem of phosphogypsum accumulation in dumps of chemical plants has been an urgent problem for several decades. The ecological situation is aggravated by the fact that more and more areas are allocated for its conservation. A negative point in the application of phosphogypsum is the intake of radionuclides and fluorine into the soil and plants, small particles could be dispersed to the atmosphere by wind. But given the presence of macro-, mezo- and microelements in it and the high price of mineral fertilizers, it is now considered as a good fertilizer and ameliorants, especially for alkaline soils. The goal of the research was to study the effectiveness of phosphogypsum application (from Sumykhimprom) and ammonium sulfate in increasing doses of nitrogen 50‒150 on the dynamics of nitrogen, phosphorus, potassium, calcium and hydrolytic acidity of typical middle loam black soil. An increase in nitrogen led to growing the content of hydrolyzed, nitrate and ammonium forms of nitrogen in the soil. The maximum availability of N-NO3 in the soil is characteristic for the first period of sampling, in the tillering stage. At this period, the maximum difference is observed between the control and fertilized variants of the experiment. The application of phosphogypsum with N150 almost threefold increased the content of nitrates in the soil. Variants with lower doses of nitrogen also affect the accumulation of nitrates in layers 0‒20 and 20‒40 cm. After harvesting, an insignificant difference was found between the control and fertilized variants (except for N150) with a general decrease in the level of nitrate availability to 0.1‒0.2 mg/100 gm of soil. The impact of fertilizers was less on the content of labile phosphorus and exchangeable potassium. A year after fertilization, a significant increase in the value of hydrolytic acidity is observed in the fertilized variants.
 It is especially noticeable at a dosage with nitrogen of 120‒125. In these variants, the hydrolytic acidity in both the arable and subsoil layers exceeds 4 mmol+/100 gm of soil. Changes in the content of water-soluble calcium are insignificant which can be explained by the fact that the solubility of calcium sulfate is not high enough and it takes more time for calcium to appear in an ionic form.