Effects of thermal shock and pre-sprouting on field performance of potato in Estonia

Pre-sprouting (PS), and to a lesser degree, pre-planting thermal shock (TS) had positive effects on tuber yield and other performance indicators. The experiment was carried out during the 2000, 2001 and 2002 growing seasons in the Department of Field Crop Husbandry of the Estonian University of Life Sciences. An untreated control (0) was compared with TS (2 days at 30 ο C, then 5 days at 12-15 ο C in a lighted room just prior to planting) and PS (35-38 days before planting in a humid (85-90%) and lighted room at 12-15 ο C). All treatments were applied to three varieties: 'Agrie Dzeltenie' (early), 'Piret' (medium early) and 'Ants' (medium late). In the present study, the TS accelerated the emergence of plants by 2-5 days and PS by 7-12 days. Averaged over 3 years and 3 varieties, maximum leaf area index (LAI, 3.9 units) was reached 74 days after planting (DAP) and on the 50 th day after emergence. Maximum LAI was 3.7 at 72 DAP for PS, 3.8 at 73 DAP for TS, and 4.1 at 76 DAP for the control. TS accelerated the beginning of tuber formation by about 5 days compared to the control, but the tuber yield of the control equalled TS from 65 days onward. Tuber formation began even slightly earlier in the PS treatment, and tuber yield exceeded PS throughout the season. All treatments reached maximum yield by 120 DAP.