No abstract

Currently, in the Russian Federation there is a tendency towards a decrease in the content of organic substance in the soil and its acidification. It is impossible to stop these processes without applying organic fertilizers and calcium containing ameliorants. Their effect on the soil properties depends on the edaphoclimatic conditions. In order to study the effect of fertilizers and ameliorants on the fertility of leached chernozem in the forest-steppe zone of the Central Black Earth zone of the Voronezh region in 2018 – field experiments were conducted. The results showed that prolonged application of mineral fertilizers led to the acidification of the soil both against the background of exposure to organic substances and liming. Reliming calcification of the leached chernozem contributed to a noticeable decrease in soil acidity (pHKCl increased by 0.7-1.0, Hr decreased by 2.1-2.9 mg-Eq/100 g of soil, the content of exchange forms of calcium and magnesium increased to 26.2-26.9 mg-Eq/100 g of soil). Some optimization of the acidity of the soil was also observed even with the reapplication of manure. The calcification of the soil led to the optimization of its fractional-group composition of humus.

An objective assessment of the ability of the soil to supply plants with potassium is possible only when determining a set of indicators - the content of various forms of potassium in the soil and the degree of their mobility. In this regard, we conducted studies to study the effect of long-term fertilizer and ameliorant application on the content of various forms of potassium and potassium buffer capacity of the soil. The studies were carried out in a field experiment laid down in 1986. A six-field crop rotation was mastered in the experiment. We studied 7 options for experience. Soil samples were taken after the fifth rotation of the crop rotation. The results showed that long-term fertilizer application creates quite high reserves of various forms of potassium in the soil. The most intensive accumulation of forms available for plant nutrition (mobile and metabolic) was facilitated by the introduction of mineral fertilizers against the background of organic aftereffects. The use of ameliorant leads to the increase in non-exchange fixation of potassium. The study of the potential buffering capacity of leached chernozem with respect to potassium showed that even with a sufficiently high content of its mobile and metabolic forms, the soil can be characterized by a deterioration of the potash state.

The paper studies the processes of transformation of the molecular structure of humic (HA) and fulvic acids (FA) of leached chernozem under the influence of fertilizers and meliorant. The research was carried out under the conditions of many years of stationary experiment of the Department of Agrochemistry, Soil Science and Agroecology of the FSBEI HE Voronezh SAU. Samples of leached low-humus thin heavy-loamy chernozem were analyzed. The isolated and purified preparations of HA and FA were studied on a SM2203 spectrofluorimeter in the ultraviolet and visible ranges. The paper also presents the results of determining the most important physical and chemical properties of soil variants using various fertilizer and meliorant systems. Limed variants have optimal indicators. Based on the analysis, it can be assumed that the FA molecules of the variant with a double dose of mineral fertilizers on the background of manure differ in a developed aliphatic part, have many auxochromic substituents. HA of the same variant are characterized by a high condensation of nuclear structures. The HA and FA molecules of the variant with the joint application of fertilizers and meliorant have a more complex structure of the nuclear and peripheral parts. According to the results of calculations of extinction coefficients, it was found that liming contributes to the accumulation of more mature forms of humic acids.

There is no alternative to soil liming as an environmental protection measures. It is difficult to overestimate the role that the application of calcium ameliorants has on soil properties. But besides a positive effect on soil properties, liming leads to some deterioration in the conditions of potassium plants nutrition. For studying this circumstance, researches were carried out in a long-term stationary experiment on leached chernozem in sugar beet agrocoenosis in the Voronezh region. It is established that the application of mineral fertilizers in doses of NPK of 120 and 240 kg / ha has resulted in a decrease of exchangeable calcium content in comparison with the backing variant by 0.7–1.2 mg-eq. / 100 g of soil. At the same time, there was an increase in soil availability of exchangeable potassium by one class in contrast with no treatment. In the case of soil liming, this process was less revealed — soil availability with exchangeable potassium remained at the level of control. With the application of mineral fertilizers on the back of organic aftereffect, the content of fixed potassium increased. The use of N120P120K120 provided 26 mg / kg of soil for a higher content of fixed potassium than the application of N240P240K240. The highest content of fixed potassium was observed with a joint consequence of manure and defecation - 649 mg / kg of soil. An increase in the activity of calcium ions in the soil led to a decrease in the activity of potassium ions. The interinfluence of these indicators was intensified by applying calcium ameliorants into the soil. The correlation coefficient between the pCa value and the potassium potential of the non-liming soil was - (–0.675) before sowing sugar beet and (–0.684) before harvesting, and on the ameliorated variants (–0.814) and (–0.500), respectively. Applying mineral fertilizers on various grounds increased crop yield by 16.0–18.2 t / ha in comparison with no treatment.