Increasing the Payback of Nitrogen Fertilizing of Winter Wheat with the Use of Original Methods for Calculating Their Optimal Doses

In the central zone of the Krasnodar Territory of the Russian Federation, on the pre-Caucasian low-leached heavy-duty chernozem on the basis of the P.P. Lukyanenko National Grain Center, for more than 15 years, new, more effective methods for calculating optimal doses of nitrogen fertilizing of winter wheat, characterized by high payback, have been studied. The methodological basis of the study was the assumption that when calculating optimal doses of nitrogen fertilizers, it is necessary to take into account the initial level of effective soil fertility, the state of agrophytocenosis and the planned yield. The solution of this problem is possible only with the help of a systematic analysis of the relationship of winter wheat yield with the above factors, the construction of a regression multiple nonlinear mathematical model and mathematical modeling of various situations in the search for optimal doses of top dressing. As initial information, the data obtained in long-term multifactorial field experiments were used, which resulted in the development of 2 new methods for determining the optimal doses of nitrogen fertilizing of winter crops (first and second) that meet the above requirements. The results of 3-year field experiments to study the effectiveness and payback of nitrogen fertilizing of winter wheat, depending on the methods of their calculation, are presented. The agro-climatic conditions at the time of the research, although they were different, but in general turned out to be relatively favorable for obtaining a good harvest of winter wheat. In 2015 and 2016, comparative tests of the effectiveness and payback of 2 new methods for calculating the optimal doses of the 1^st and 2^nd nitrogen fertilizing of winter wheat were carried out. For comparison, 2 well-known, widely used in practice, “tabular” methods were selected (prototypes 1 and 2). In 2015, the study was carried out with the Grom variety (predecessor - corn for grain), in 2016 - with the Yuca variety (predecessor - winter wheat). It is shown that the use of original methods for calculating optimal doses of 1^st and 2^nd nitrogen fertilizing of winter wheat significantly increased their efficiency and payback (both 1^st and 2^nd in total) compared with the prototypes (by 35-200%), at the same time, the payback of nitrogen top dressing, the doses of which were calculated from the prototypes, was ~12- 14 kg/kg (on average for 2 years), and the payback of top dressing calculated according to the original methods was 22-24 kg/kg in 2021 (forerunner - soy, Adel and Bagrat varieties) studied the effectiveness and payback of nitrogen fertilizing when calculating their doses only by original methods. It was shown that even with a high level of yield of winter wheat in the control (~60 c/ha on average for both varieties), the use of 2 nitrogen fertilizing, the doses of which are calculated according to the original methods, allowed to achieve a yield of winter wheat of 80-90 c/ha with a payback of ~22 kg grains/kg of N fertilizers.