The Effect of Time and Depth of Planting on Obtaining Planned Potato Yields

In 2014–2017 in the northern forest-steppe zone of Chelyabinsk oblast, the influence of planting dates and the depth of seed placement of potatoes on the size and quality of tubers was studied. During the study period, physical soil maturity in the first decade of May was observed twice in 2014 and 2017. The early planting of potatoes (May 5) was accompanied by an increase in the harmfulness of rhizoctoniosis (by 22.8% in the Rosara variety and by 63.7% in Kuzovok) and the Colorado potato beetle (by 26 and 43%, respectively) compared with the planting on May 12–15. The seedlings of the early variety of Rosara potato on May 30 in 2014 were damaged by frost (–1.0°C). From meteorological and phytosanitary positions, the optimum term for planting potatoes is the beginning of the second decade of May. Planting potatoes on May 12–15 with embedding of seed material to a depth of 5–6 cm ensured the formation of the planned yield of 40 t/ha with a planting scheme of 70 × 19 cm (41.4 t/ha Rosara, 44.6 t/ha Kuzovok) and additionally with the scheme 75 × 27 cm (38.3 t/ha) for the Kuzovok variety. The planting of potatoes on May 25–29 provided a predetermined level of productivity (40 t/ha) of the Kuzovok variety in all variants of the experiment, and the Rosara variety in the variant of thickened planting. However, the starch content in Rosara and Kuzovok tubers decreased by 1.60 and 1.26%, respectively, and starch collection from 1 ha decreased by 0.60 and 0.37 t/ha, respectively. The accumulation of nitrates in tubers increased by 25.8 and 52.5%, respectively, compared with the optimal planting period. Deep embedment of seed tubers had the advantage here: an increase in the yield of the Rosara variety averaged 0.88 t/ha, while that of Kuzovok was 1.23 t/ha. During the late planting period (June 5–12), there was a significant decrease in productivity (Rosara by 3.49 t/ha, Kuzovok by 5.18 t/ha) and the quality of potato tubers compared to planting of May 12–15. The starch content of tubers decreased by 1.87 and 2.11% and the collection of starch from 1 ha to 1.10 and 1.45 t/ha, respectively, while the accumulation of nitrates increased 2.05 and 2.19 times. The planned yield of 40 t/ha was achieved only in the Kuzovok variety in thickened planting variants. At the same time, deep seeding of seed material increased the yield of the Rosara and Kuzovok varieties by 1.39 t/ha and 1.90 t/ha on average. Early planting (May 5) in 2014 and 2017 did not lead to an increase in potato productivity compared to planting in the second decade of May. At the same time, the yield decrease of the Rosara and Kuzovok varieties was 5.82 t/ha and 2.75 t/ha. The planned yield of 40 t/ha was noted only in the variant of the thickened planting of the Kuzovok variety.