Sustainability of Soil Fertility in the Southern Steppe of Ukraine, Depending on Fertilizers and Irrigation

Farming in the Southern Steppe of Ukraine is mining humus and nutrients. There comes a point when soil degradation is irreversible: sustainability requires complying with the fundamental laws of agriculture-in particular, sound crop rotation and return of nutrients to balance removal by the crops. Short-and long-term field experiments on typical Kastanozen and Chernozem reveal that provision of adequate nutrients and water gives consistently high crop yields and these factors significantly change the main indicators of soil fertility: humus content, gross and moving content of NPK, and water-physical properties (as well as the content of arsenic and heavy metals). Combined use of organic and mineral fertilizers is the most effective way to stabilize crop yields and soil fertility; organic fertilizers stabilize soil structure which, in turn, enhances the infiltration of rainfall. Combined organic-mineral fertilizer in crop rotation increases the efficiency of water utilization on average by 20-30%, in very dry years by 30-40%.