ASSESSMENT OF FREEZING INJURY TO RUSSET BURBANK TUBERS IN FIELD AND LABORATORY TRIALS

Authors: Seymour, Marcus; Boydston, Rick; Brown, Charles

Submitted to: 2000 Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2000
Publication Date: 3/1/2000
Citation: SEYMOUR, M.D., BOYDSTON, R.A., BROWN, C.R. ASSESSMENT OF FREEZING INJURY TO RUSSET BURBANK TUBERS IN FIELD AND LABORATORY TRIALS. PROCEEDINGS OF THE 50TH ANNUAL WASHINGTON STATE POTATO CONFERENCE. P 109-114. 2000.

Interpretive Summary: Numerous potato tubers are left in the field after potato harvest and can become a serious problem in the production of subsequent rotation crops. Post-harvest tuber leavings represent 9 to 11 times the normal planting rate. Tubers are susceptible to freezing injury, and cold winter soil temperatures can provide good volunteer potato control. In laboratory trials, Russet Burbank tubers were exposed for various times to a range of sub-zero soil temperatures to evaluate the effects on tuber and sprout viability. Field trials evaluated winterkill of potato tubers at various soil depths and contributed to an understanding of the critical temperatures required for tuber injury and death. Potato tubers were found to freeze between 28.6 to 29.5 deg F soil temperature depending on soil moisture and tuber to tuber variation. Tubers exposed for extended periods to temperatures just above the freezing point are damaged and subsequent sprout development is weakened. Monitoring soil temperature at various depths in soil during the winter makes forecasting the severity of volunteer potato populations possible. Estimates of volunteer potato populations can be made available to growers early in the growing season, and can help them to make informed management decisions about the need for control measures or their choice of rotation crops following potatoes.

Technical Abstract: Russet Burbank tubers in air-dried soils undercooled to about 24 deg F without injury. When tubers froze, an exotherm occurred and the release of the latent heat of freezing caused tuber temperature to rise rapidly. Tuber temperature then briefly stabilized at about 29.5 deg F, which we believe is the freezing point of the tuber. Tubers that were exposed to such exotherms were not viable. Subsequent trials indicated that tubers in hydrated soils undercool to only about 28 deg F before an exotherm occurred. The release of the latent heat of freezing caused tuber temperature to rise before briefly stabilizing at about 28.6 deg F. The freezing temperature of the tuber falls between the values recorded for dry soil at 29.5 deg F and moist soil at 28.6 deg F. Potato tubers held at 30.2 deg F for all times of exposure, and at 29.3 deg F for 2 hrs were able to develop normal sprouts. Increasing the time of exposure at 29.3 deg F significantly reduced sprout development. After 12 hours exposure to 29.3 deg F some tubers exhibited catastrophic injury characterized by leakage of cellular fluids and very rapid breakdown. Most tubers exposed to 28.5 deg F for less than 2 hours produced some weakened sprouts, but 30% of the tubers were dead. After 12 hours exposure to 28.5 deg F, all tubers leaked cellular fluids were not viable. Field trials indicate that soil temperatures in the range of 27.5 to 29.5 deg F cause substantial tuber injury. In field trials, no tubers survived exposure to 25.4 deg F, and tuber injury was minimal at temperatures above 31 deg F.