Dynamics of spring wheat root system in active manifestations of drought and various secured plant nutrients
The frequency of extreme spring (SCC = 0,1) and a summer drought (SCC = 0,4) on the black soils is between one and two times in ten years, the last 30 years (1981-2010), a manifestation of severe early-spring drought mentioned twice. In extreme weather conditions, spring primary root system of spring wheat at the expense of winter moisture reserves are well developed in both crop rotations and reached a depth of 1 meter. Perennial legumes improve water physical and agrochemical properties of the soil, so the weight of roots per plant in the tillering stage reached in grain-fallow rotation 0,313 g, grain-grass 0,336 g. The secondary root system is fully developed only in the grain-grass crop rotation, where the negative effects of extreme spring and summer drought on the rate of increase and the mass of the root system was less pronounced. At the time of completion of tillering of roots in grain-fallow rotation was 73,8% and the grain-grass 60,8% of the total plant biomass. In earing their share declined to 38,0% and 34,4%, and in the phase of full maturity up to 21,3% and 19,4%. The bulk of the roots of grain-fallow rotation was placed in the soil layer 0-60cm (69%), and grain-grass in a layer of 30-80cm (70%). Mass of roots of spring wheat in grain-grass crop rotation was 28,5% and the yield is 2,2 times higher than in grain-fallow rotation. The formation of 1c grain of spring wheat in the grain-grass crop rotation took 7,1 mm of moisture in zernoparovyh 9,5 mm. In acute drought factors determining the development of the root system of spring wheat are ranked by decreasing order of grain-fallow rotation: the temperature of the soil, nitrates, moisture, pH, soil density, mobile phosphorus and potassium; grain-grass: soil temperature, pH, moisture the movable phosphorus and potassium, soil density, nitrates.