Effect of tillage on productivity of crop rotation and nitrate contain in topsoil under unstable of atmospheric precipitation

Received 25.12.2018 Received in revised form 07.05.2019 Accepted 19.08.2019 Available online 01.09.2019 The aim of the work was to identify the presence of a relationship between the productivity of grain-row crop rotation and the content of nitrates in the topsoil with different ways of its main tillage. Eight-year monitoring was conducted within a long stationary field experiment on the territory of the experimental farm of NSC ISSAR in Donetsk region. The content of nitrate nitrogen in chernozem ordinary was determined on three soil treatment options moldboard ploughing, subsurface non-turning soil tillage and no-till. At the same time, the dynamics of weather conditions was observed and the hydrothermal coefficient of Selianinov (HTC) was calculated. Statistical data processing was performed by correlation, regression and ANOVA analysis in a sample of the results of 729 individual observations. It is shown that after a twoyear drought, an increase in yield occurs along with an increase in the content of nitrates in the soil on all variants of soil treatment. However, a year after the overmoistening, the yield decreases, despite the still high level of nitrate nutrition. In years with critically low humidity, the greatest yields are recorded on moldboard plowing. By comparing the treatment efficiency without soil turnover and the conventional moldboard plowing, we determined the conditions under which minimization of tillage is advisable. With an increase in the degree of minimization of tillage, the positive peak on the graph of the relative yields dynamics decreases and the negative one deepens. With no-till, the productivity of crops decreases in years with a HTC less than 0.6 at the same time as a decrease in the nitrate content in the soil. For no-till, a positive correlation was also determined between the level of nitrate content in the soil last year and the crop yield in the following. It was found that the non-use of plowing increases the risk of negative effects of excessive soil moisture if the nitrate content is high. It has been proven that a lack of nitrogen is not a factor in determining yields under subsurface non-turning tillage. However, with no-till, the decrease in yield is due to a decrease in the content of nitrate nitrogen in the soil, which has a long-term effect. Based on this, it is possible to predict the effectiveness of the direct sowing system. The regression analysis determined the dependence of the relative yield for no-till on the relative content of nitrates in the soil of the previous year (r = 0.950).