Indicators of optimal soils conditions for crop growing and preserving soil fertility in Rostov region and North Caucasus under irrigation conditionsViktor Zhurba, Nadezhda Gordeeva, Irina Mehantseva, Alina Golubeva, Yana Kabanova, Kamila Shapovalenko and Milena DavydovaE3S Web Conf., 135 (2019) 01086DOI: https://doi.org/10.1051/e3sconf/201913501086