The influence of the aftereffect of long-term use of mineral fertilizers on sorghum grain productivity and quality on ordinary blackearth of the Central Pre-Caucasus

There have been presented the study results of the experiment of the Geographical Network of Experiments with fertilizers, established in 1975 on ordinary chernozem under conditions of unstable moisture in the Stavropol Territory. The purpose of the current study was to reveal the influence of the aftereffect of the long-term use of mineral fertilizers on the agrochemical properties of soil, productivity, and quality of sorghum grain, depending on the weather conditions of the year. There has been established that, after 30 years of action and 14 years of aftereffect of the use of phosphorus fertilizers in doses of 60–180 kg/ha of a.i. the content of residual phosphorus in the soil layer of 0–20 cm before sowing sorghum varied from 25 to 55 mg/kg. The crop productivity was closely dependent on weather conditions and the agrochemical condition of the soil. In arid conditions in 2020, the largest grain productivity (2.5–3.16 t/ha) was obtained in areas of phosphorus fertilizer’s aftereffect with a high content of P2O5 in soil (more than 30 mg/kg). In the wet year, the largest productivity (5.10–5.64 t/ha) were obtained in nitrogen fertilizers’ aftereffect against the background of low phosphates availability (12–16 mg/kg). In different weather conditions, the maximum level of sorghum productivity was obtained in the aftereffect of complete mineral fertilizer or with a balanced nutrient regime of the soil, in 2020 it was 3.81–4.96 t/ha and in 2022 it was 5.4–6.14 t/ha. Sorghum grain quality was also determined by the weather and soil properties. Grain with the highest crude protein percentage (9.9–13.6 %) was obtained in a dry year after the effect of nitrogen fertilizer. In both years of the study, the products obtained after the application of high doses of one phosphorus fertilizer (120–180 kg/ha a.i.) had the least nutritional value. The crude protein percentage in grain did not exceed 2.2–7.8 %. To stabilize productivity and increase the nutritional value of sorghum, it is necessary, first of all, to optimize the nitrogen nutrition of plants, especially in conditions of good moisture supply.