Soil-Biogeochemical Aspects of Arable Farming in the Russian Federation.

Soil-biogeochemical aspects of the current state of arable land in the Russian Federation are discussed. Considerable transformation of Russian agriculture has led to structural changes in the agricultural land use, including arable farming. About forty million hectares of former arable land have been abandoned and converted into the category of abandoned lands subjected to overgrowing with meadow and woody vegetation. The restoration of natural vegetation in postagrogenic ecosystems is accompanied by changes in the biological productivity and composition of vegetation on agricultural land in general. The reduction of plowlands and their transformation to abandoned lands have changed the carbon budget. In the early 1990s, arable farming was the net source of C-CO2. At present, the total arable land area in Russia is estimated at approximately 80 M ha. This area is a source of about 20 Mt C-CO2/yr. Forty million hectares of former arable land have turned into the sink of C-CO2 of about 40 Mt/yr in size. Thus, the entire agricultural land in Russia functions as the net sink for atmospheric CO2 at the rate of 20 Tg C/yr. This fact can be considered a contribution of Russian agriculture to the goals of the "soil 4 per mille" international program assuming carbon sequestration in agricultural soils. Changes in the agricultural land use patterns together with a sharp decrease in the application of all kinds of fertilizers have led to prevalent biogeochemical flux of nutrients (N, P, K) from arable soils to urbanized areas. The deficient nutrient budget implies that the soil-climatic potential and the potentials of other factors increasing farming productivity (new varieties, plant-protective chemicals, etc.) are not fully realized in agricultural production. In 25 years (1992–2016), the uptake of nutrients by crops from arable land comprised 91, 33, and 90 Mt for N, P2O5, and K2O, respectively. The amount of applied fertilizers in that period was only about 28 Mt for N, 10 Mt for P2O5, and 28 Mt for K2O. The highly deficient budget of phosphorus is of special concern. Under these conditions, it is necessary to significantly restrict the export of apatite concentrate and phosphate fertilizers as strategic (nonrenewable) resources necessary for ensuring the food security of Russia for decades ahead. [ABSTRACT FROM AUTHOR]