Variability of nutrient regime characteristics in irrigated soil under different fertilization systems

Abstract

The article highlights the results of a research covering the influence of irrigation and different fertilization systems on the nutrient regime of typical heavy loam chernozem (Chernic Phaeozem) as an indicator of its quality. The research conducted in a long-term stationary field experiment of the Institute Of Vegetable And Melon NAAS (Kharkiv Region) under drip irrigation with suitable water. According to the analysis of meteorological conditions, during the growing season in the years of the study, the amount of precipitation was lower than the average long-term value, and the air temperature, on the contrary, was higher. The state of vegetation and soil on 8 variants with different fertilization systems under two crops of vegetable and fodder rotation was investigated. The content of nutrients, humus and pH in the soil at the end of the growing season of crops monitored. The dynamics of plant development analyzed using the NDVI and NDMI spectral indices for biomass and plant stand density indicators as indicators of soil nutrient and moisture availability. In 2022, for the cultivation of beets, the highest NDVI values (0.72–0.75) and, accordingly, the best state and density of vegetation recorded in August with the saturated green color of the growing plants. The maximum values of the moisture index (NDMI) (0.47) are in July, which characterizes the density of plants as high and no water stress. For the cultivation of barley with subsowing of perennial grasses in 2023, the highest plant density and formation of green phytomass recorded in June and at the end of August. NDMI values this year were lower than last year, indicating lower soil moisture due to lack of irrigation and dry conditions of the year. It found that during long-term irrigation with hydrocarbonate water, there was an increase in soil pH_H2O values compared to the initial data before the start of irrigation. However, the reaction of the soil environment in the 0–30 and 30–50 cm layers classified as neutral. On variants with different fertilization systems, the content of organic carbon in the soil was significantly higher than on the control, and ranged from 2.25 to 2.44 % (layer 0–30 cm). Under different fertilization systems, the content of mobile nutrient compounds was characterized by variability and higher values compared to the control. At the end of the growing season, the degree of saturation of the soil with mineral nitrogen in the variants of the experiment with organic, organo-mineral and biological fertilization systems was classified as low, with the exception of the variant with an intensive fertilization system (high). The content of mobile phosphorus compounds corresponded to a very high level, and the highest values were for the combined application of organic and mineral fertilizers in crop rotation; the potassium content mostly assessed as high and very high. The highest level of yield was fixated with organo-mineral fertilization system.