Methods of primary soil treatment in a crop rotation and productivity of sunflower

A purpose of the work was a search of ways to increase productivity of crops, including of sunflower, during minimization of the systems of the primary soil treatment in a crop rotation in the droughty environments of the south steppe of Ukraine. The researches were conducted in two-factor trial on unwatered plots of the experimental fields of the Institute of the irrigated agriculture of NAAS of Ukraine during 2011-2013. Soil of the experimental plot is dark-chestnut middle loamy with humus content in the arable layer 2.2% and the least moisture capacity in a meter soil layer up to 21.5%. Establishment and carrying out of trials, selection of soil samples, analyses and observations were conducted according to the generally accepted methodologies. In the droughty environments of the south steppe of Ukraine the system of soil treatment in a crop rotation influences significantly on formation of its water and nutritive regimes. Small subsoil treatments promotes the best accumulation of moisture in a 0-30 cm layer of soil and its average content for all the period of vegetation exceeded a variant with a deep subsoil treatment on 1.3 mm, and variant with ploughing - on 1.4 nun. A higher content of nitrates and mobile phosphorus in a variant with moldboard promoted the best formation of sunflower yield. The highest productivity of 2.37 t/ha was in a variant with mold- board in a depth 28-30 cm, and the least productivity was 1.96 t/ha in a variant with small subsoil treatments in a depth 12-14 cm. An increase of sunflower