The effect of green manure on the agrochemical properties of soil in winter wheat crops, yield and grain quality

The nitrogen and biological potential of the soil is largely determined by the amount of fresh plant material, its chemical composition and the nature of accumulation over time. Studies on the effect of sideration on the agrochemical properties of the soil, yield and grain quality of winter wheat were conducted during 2019–2023 in the link of crop rotation: sideral steam – winter wheat – corn for grain – barley. The territory of the experimental site is included in the foothill continental zone of a moderately warm climate with moderate humidification of the Kabardino-Balkarian Republic. The soil of the experimental site is ordinary medium–sized slightly washed clay chernozem on carbonate clays. The humus content is 4.6%. All the sideral crops (peas, spring vetch, white mustard, Sudanese grass) were plowed during the flowering phase. The object of research is the medium-ripened winter wheat variety Alekseich, zoned for the North Caucasus region. The results of a qualitative analysis of the plant mass of sideral crops with an assessment of the ratio C:N. It was revealed that the vegetable mass of white mustard is characterized by a narrower ratio of carbon to nitrogen in the experiment (11:1), which leads to an increase in the biological activity of the soil under the agrocenosis of winter wheat and the mineralization of organic substances. The Sudan grass is characterized by a wide C:N ratio in the experiment (19:1). An inverse correlation was found between the yield of winter wheat and the C:N ratio in the biomass of sideral crops (r = –0.91785), which means that the wider the C:N ratio in the plant mass of sideral crops entering the soil, the lower the level of nitrogen nutrition and yield in the first year of sideration. It is shown that the most favorable nitrogen regime of ordinary chernozem during the growing season of winter wheat Alekseich is characterized by variants of sideration with peas and white mustard: the excess nitrogen content of the control variant is 17%. According to the quantitative content of phosphorus and potassium in the soil of the agrocenosis of winter wheat during the growing season, the variants of sideration with peas and spring vetch are distinguished. In the pea sideration variant, the phosphorus content in the soil on average exceeded its content in the soil of the control variant by 54%, and in the spring vetch sideration variant by 42%. According to the potassium content in the pea and spring vetch cider variants, the excess potassium content in the control variant was 30.1 and 26.5%, respectively. White mustard sideration increased the phosphorus content in the soil by only 4.2% relative to the control variant, due to a lower intake of this element from the plant mass. On average, over three years, the yield of winter wheat of the Alekseich variety in the white mustard cider variant increased by 1.29 t/ha or 24%, with pea and spring vetch cider by 9 and 6%, respectively, relative to the control variant. The plowing of sideral crops increases the amount of nitrogen available to winter wheat plants, which is subsequently used by them in the reutilization of nitrogen from the leaves into the forming seeds, which improves grain quality. On average, over three years, the yield of winter wheat of the Alekseich variety in the white mustard cider variant increased by 1.29 t/ha or 24%, with pea and spring vetch cider by 9 and 6%, respectively, relative to the control variant. In the cider variants, the nitrogen content in the grain increased by 2–8%. The option of white mustard sideration provided the maximum yield of protein with a harvest in the experiment, exceeding the control values by 29%.