Role of biological nitrogen in agriculture in Russia

The nitrogen balance used to form the crop yield and the proportion of biological nitrogen in it were evaluated. New data on the contribution of biological nitrogen to the agroecosystems of Russia have been obtained, which showed that in the total nitrogen intake (≈3 million tons of active substance) the share of biological nitrogen is 34.7%, which is 3 times more than nitrogen supplied with organic fertilizers (11.6%). In the composition of biological nitrogen, half of it (50.1%) belongs to nitrogen fixed in crops of perennial legumes. The amount of nitrogen fixed in soybean crops was 23.1%, and leguminous crops – 19.3%. Over the past 15 years, the amount of symbiotic nitrogen has increased from 544.3 to 1025.7 thousand tons, or 1.88 times due to an increase in the acreage of legumes and their yield. The intake of biological nitrogen from legumes increased by 2.55 times, soybeans – by 2.91, and perennial legumes – by 1.69 times with a decrease in the proportion of nitrogen fixed in crops of annual grasses. Agricultural plants consume 5.38 million tons of nitrogen to form a crop, and nitrogen removal from the alienated part of the crop reaches 3.24 million tons/year. In agriculture in Russia, on average, ≈3 million tons of nitrogen enters the soil per year together with mineral and organic fertilizers, as well as as part of biological nitrogen. When calculating the cost of nitrogen for the formation of the entire crop, the nitrogen balance is formed sharply negative (–2.44 t/ha/year). When calculating nitrogen costs for the commodity part, the average annual balance becomes close to optimal (–0.30 t/ha/year).