Dependence of yield and quality of potato tubers on the time and the depth of seed material planting
In the forest steppes of Chelyabinsk region potato yield in 2014-2017 varied depending on the level of mineral nutrition (the factor contribution is 59%), variety (10.5%), density (20%) and planting time (7.5%); the depth of the seed material planting had a significant, but extremely less impact (0.5%). The optimal time for planting potatoes to provide the greatest yield and product quality is the 12-15 of May. The planting potatoes in the third decade of May causes a decrease in the content of dry matter in tubers (Rosara by 1.8%, Kuzovok by 1.3%) and starch (by 1.6 and 1.3%, respectively), increases the accumulation of nitrates by 1, 26-1.52 times higher as compared with planting in the second decade of May. The late planting reduced the yield of Rosara and Kuzovok varieties by an average of 3.5 and 5.2 t/ha, the dry matter content in tubers by 2.7 and 2.9%, starchiness by 1.9 and 2.1%, respectively, while the accumulation of nitrates increased 2.05 and 2.19 times as compared with the optimal planting time. When potatoes are planted early, a significant increase in yield is ensured by the fine planting of seed tubers (Rosara 1.3 t/ha, Kuzovok 1.4 t/ha), and when paptatoes are planted late, it is necessary to plant potatoes to the depth of 10-12 cm (Rosara 1.4 t/ha, Kuzovok 1.9 t/ha).