Increasing efficiency of irrigation reclamation in potato and soybean agrocenoses using sludge

The purpose of the study was to assess effect of different doses of wastewater sludge on productivity of irrigation water use by agrocenoses of potatoes (Zhukovsky rannii) and soybeans (VNIIOZ 31), on their yield, as well as the index of soil contamination and seed production. Agrometeorological conditions of the periods of vegetation experiments are characterized as dry with hydrothermal coefficient value of no more than 0.39. Considering the current climatic conditions, regulations for watering potatoes and soybeans were drawn up. It was established that application of WWS in doses of 20, 40 and 60 t·ha-1 had different effects on crops total water consumption. In potato crops, irrigation rate varied from 2590 m3·ha-1 in the control to 1850 m3·ha-1 in WWS60 variant, and in soybean crops, it varied from 3700 in the control to 2960 m3·ha-1 in WWS60 variant. At the same time, amount of irrigation water to obtain a ton of potato and soybean yield in the control averaged 124.5 and 1298.2 m3·t-1, respectively, against 118.3…72.8 and 1213.1…886.2 m3·t-1 for variants WWS20, WWS40 and WWS60, which corresponded to increase in water use productivity from 5.0 to 41.5 % and from 6.6 to 31.7 %, respectively. Laboratory studies of soil samples of the arable layer showed that pollution index in relation to heavy metals Cd, Pb, Zn, Cu varies from 2.54 in variant WWS20 to 4.04 in variant WWS60, which indicates the absence of soil contamination. Evaluation of potato tubers for values of starch, dry matter, nitrates and heavy metals demonstrates sufficiently high quality and acceptable level of contamination of the seeds.