The objective of this research is to study the pattern of soy root system growth and distribution in soil under drip irrigation. The research was conducted in 2011-2013 at light chestnut soils at the territory of experimental farm “Oroshayemoye” situated in the Sovetskiy district of Volgograd. The area of experimental field was 3 ha. Soil bulk density was determined by the technique of A. N. Kachinskiy taking soil samples in-situ layer-by-layer from 0 to 1.5 m in 5 to 6 replicates by means of soil drill BP-500 and BP-100. Soil bulk density was determined in every 0.1 m to a depth of 1.0 m, and deeper – in every 0.2 m. The density of soil solid phase was determined by pycnometry method in the same layers. The mass of roots was determined according to the technique of N. Z. Stankov. It is established that water and nutritional regimes of soil have a significant impact on formation of soy root system. The main mass of soy roots is situated in the soil layer 0-0.3 m. For cultivar VNIIOZ 86 the dry mass of roots in the layer of 0.1-0.2 m was 0.51 t/ha (35.7 %) under preirrigation threshold of 70 % FC in 0.6 m soil layer. For cultivar VNIIOZ 11 the dry mass of roots in the layer of 0-0.6 m was 1.83 t/ha (40.7 %) under preirrigation threshold of 80 % FC in 0.6 m soil layer. Applying fertilizers by the dose of N120P80Ê50 kg of active substance per hectare and maintaining soil moisture higher than 80 % FC provide increasing of root mass for cultivar VNIIOZ 86 up to 2.18 t/ha, or by 0.21 t/ha. The obtained data confirm that in arid zone of Volgograd region irrigation has more significant impact on soy root system development than the doses of applied fertilizers.
Keywords: soy, consumptive use, irrigation, soil moisture, irrigation regime, root system, depth of moisturizing.
