CHANGES IN SOIL AGROCHEMICAL PROPERTIES UNDER DIFFERENT TILLAGE METHODS DURING THE GROWING SEASON OF FIELD CROPS IN SOUTHERN UKRAINE

Abstract

Purpose. To investigate changes in the content of major nutrients and organic matter in the soil under adverse weather conditions as influenced by various tillage practices.
Methods. Mathematical, statistical, and laboratory- analytical methods were used in the study. Soil samples were collected twice a year from the 0–30 cm soil layer. The following parameters were determined in the collected samples: organic matter content, mineral nitrogen content, available phosphorus and potassium compounds, and water pH. CO2 emission from the field surface was determined using the absorption method. All analyses of the soil samples were conducted in accordance with current standards. Statistical and correlation analyses of the obtained data were performed using Microsoft Excel, Agrostat, XLStat, and Statistica software.
Results. The field experiment was conducted during years characterized by unfavorable weather conditions for the studied agricultural crops. The soil pH values across all treatments did not differ significantly at the beginning of the growing season, ranging from 7.31 to 7.47. After harvesting, the soil acidity was within the range of 7.36–7.51. A slight increase in soil pH during the growing season is typical under arid conditions. An expected decrease in the mineral nitrogen content was observed throughout the growing season. On average, this parameter decreased by 28.6–32.3 %. In spring barley crops under no-till practice, the available phosphorus content decreased by 15.8 %, while under minimum tillage, it decreased by 32.6 %. This parameter fluctuated widely but did not correlate with the tillage method. The dynamics of the exchangeable potassium content were more complex. While a decrease was observed in the conventional tillage treatments, the exchangeable potassium content increased by 16.8 % under no-till barley and by 6.3 % under minimum tillage sunflower. The soil organic matter content in barley crops significantly depended on the tillage practice. Under conventional tillage, the organic matter content decreased by 2.3 %, whereas under minimum tillage, it decreased by only 0.8 %. In the no-till treatment, a 1 % increase in the organic matter content was observed. Correlation analysis revealed a strong negative correlation between CO₂ emissions from the field surface and the soil organic matter content. These data make it possible to assess the impact of soil microbiota activity on soil organic carbon accumulation.
Findings. The conducted research provided quantitative data on changes in several soil agrochemical parameters during the growing season under the influence of adverse weather conditions. Across all experimental treatments, a consistent decrease in the mineral nitrogen content in the arable soil layer was observed, averaging 30.3 %. The available phosphorus content also decreased across all treatments. The dynamics of exchangeable potassium and organic matter significantly depended on the tillage practice. By the end of the growing season, the soil organic matter content in the spring barley crops under the no-till treatment increased by 1 % compared to its baseline value at the beginning of the growing season. Soil fertility, as well as the opportunity for regional agricultural enterprises to participate in the generation and trading of carbon credits, depends on the accumulation of soil organic matter. Given this, it is recommended to reduce mechanical soil disturbance, and particularly to implement no-till farming, for cultivating field crops in Southern Ukraine