IMPACT OF DRIP IRRIGATION WITH DIFFERENT FERTILIZER SYSTEMS AND WATER QUALITY ON SOIL ECOLOGICAL FUNCTIONS

Management practices to improve irrigated soil ecological functions is important for landscapes supporting plant growth and establishment; however, the science-based knowledge on the impact of variable fertilization and water quality under drip irrigation to evaluate soil ecological functions is lacking in Ukraine. The goal of our research was to evaluate the impact of drip irrigation using diverse fertilization and water quality on the ecological functions of loamy textured Southern Chernozems for sustainable management of apple orchards at two different locations in Southern Ukraine. Field experiments were established in 2009 by applying diverse fertilizer sources – organo-mineral (at 9 dm3/ha), mineral (at N120 P30-90K75-120) and organic (at 7 dm3/ha) under drip irrigation with different water quality (suitable vs. partially suitable – I & II categories) to maintain 75-80% field moisture capacity to a 60 cm depth. Based on field, laboratory, statistical and calculation-comparative research methods, selected chemical, physical, and physicochemical soil properties in the wetting zone, at the boundary of the wetting zone, and in the irrigated rows were determined. Results have shown that fertilizer sources especially mineral fertilization exerted most pronounced effects on soil functions than that of the water quality. A higher amount nitrogen (N) was available from the mineral fertilizer, as compared to organic- and integrated sources, to by the growing apple trees. A significant decrease in easily hydrolyzed N content in the soil was observed during the spring-summer seasons, when the N uptake by roots was maximum to support for healthy apple orchard establishments. Moreover, post-applied mineral N was adequately utilized by the apple trees with a significant reduction in available N leaching into the deeper soils. The available potassium and phosphorus contents in the soil had increased gradually after three years of fertilization and the application of mineral fertilizers with partially suitable water (II category) using for drip irrigation had the highest synergistic impact. Stable acidification of the soil with variable water quality was highest under mineral fertilization than that of other fertilizing inputs. Soil absorption complex (with exchangeable cations) in the wetting zone significantly differed as compared to the irrigated rows due to significant changes in the absorbed calcium, sodium and magnesium concentrations. With soil structural heterogeneity in terms of agronomically important aggregates, the wetting zone soil aggregates were slightly dispersed within 10 cm depth but stable up to 50 cm depth. Based on our research, it is concluded that drip irrigation with diverse water quality significantly improved soil ecological functions under mineral fertilization to support for the growth and development of apple orchards