Fixed nitrogen in agriculture and its role in agrocenoses

Received: February 23rd, 2021 ; Accepted: May 12th, 2021 ; Published: May 19th, 2021 ; Correspondence: [email protected] typical low-humus black soils in short crop rotations with legumes (25–33%) and without them, it was found that depending on the set of crops in crop rotation and application of fertilizer rates, nitrogen yield per crop is from 355 kg ha-1 to 682 kg ha-1 . The recommended fertilization system provided nitrogen compensation for crop yields by only 31–76%. Hence, in the plant-fertilizer system nitrogen deficiency varies from 161 to 370 kg ha-1 . The greatest nitrogen deficiency in the soil is observed in crop rotation without the use of fertilizers with the following crop rotation: peas-winter wheat-grain maize-spring barley. The main source of nitrogen for plants is soil nitrogen. In crop rotations with legumes, biological nitrogen is supplied from the air, which in quantitative terms per rotation in crop rotations with peas is 109–288 kg ha-1 , with soybeans 264–312, and with alfalfa 486 kg ha-1 . Biological nitrogen in crop rotations with peas and soybeans is reimbursed from 25 to 62%, in crop rotation without legumes - 9% (non-symbiotic nitrogen fixation), and in crop rotation with alfalfa - 89% of the total nitrogen removal with the crop

Synthesis of Acrylates From Methyl Propionate, Propionic Acid and Formaldehyde in the Gas Phase on Solid Catalysts

Development of active and selective catalysts for the process of obtaining methacrylic acid and methyl methacrylate from methyl propionate, propionic acid and formaldehyde is one of important stages to industrial implementation of this process. In order to solve this problem, we designed catalysts based on oxides of boron and phosphorus that were promoted by oxides of zirconium, tungsten and bismuth with varied content of oxides. The effect of temperature was examined on the conversion of reagents, the selectivity of formation and the yield of methyl methacrylate and methacrylic acid on the created catalysts. With increasing temperature, the conversion increases, the selectivity of formation of acrylates decreases and the total yield of acrylates has the maximum. It was found that without adding methanol, the optimal catalyst by acrylates yield is the one, in which the molar ratio of the ZrO2:WO3 promoters is 0.15:0.15. The total yield of the target products at optimum temperature of 593 K is 52.3 % with the total selectivity of their formation at 96.4 % and the conversion of reagents of 54.2 %. We determined the effect of adding methanol to the reagent mixture. Adding methanol increases the ratio of products MMA/MAA, and the optimal catalyst by the total selectivity of formation of the target products is the one promoted by bismuth oxide with the molar ratio of Bi2O3/Р2О5 – 0.3, which at a temperature of 593 K provides for the selectivity of formation of acrylates of 100 % with the yield of 33 %. The maximum total single­pass yield of MMA and MAA on this catalyst at a temperature of 623 K is 51.5 %, at the total selectivity of their formation of 91.6 %. However, the share of MMA in products is lower in comparison to the catalyst, promoted by the mixture of tungsten and zirconium oxides