Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2006
Publication Date: 8/1/2006
Citation: Boydston, R.A., Seymour, M.D., Brown, C.R., Alva, A.K. 2006. Freezing behavior of potato (solanum tuberosum), cultivar 'russet burbank' tubers in soil. American Journal of Potato Research. 83: 305-315. 2006. Interpretive Summary: Potatoes remaining in the ground after a typical commercial potato harvest can persist and become a weed problem in the next crop. Volunteer potatoes are a major weed problem in potato rotations in regions with mild winter soil temperatures. When winter soil temperatures at the depth of buried potato tubers are cold enough, tubers die. The critical soil temperatures needed to kill tubers has not been reported. Previous research on potato tuber freezing was conducted in a soil-less medium (air). However, tubers in soil may behave differently than those in air due to ice nucleation sites associated with soil and soil water. These studies identified the freezing behavior of potato tubers in dry and hydrated soil. Tubers were often able to supercool to –3 to -7 C in dry soil without undergoing injury. The freezing point of tubers in hydrated soil was – 1.9 C. Field experiments in the Columbia Basin of Washington indicated tubers buried at shallow depths were much more likely to experience lethal cold temperatures than tubers buried deeper. In general, when minimum soil temperature at tuber depth reached the critical range of -1.5 to -1.9 C or lower, tuber mortality occurred. Monitoring of winter soil temperatures by depth in potato growing regions could be used to predict severity of volunteer potato for the subsequent growing season and allow growers to make early decisions on control measures and rotational crops.
Technical Abstract: Volunteer potatoes are a major weed problem in potato rotations in regions with mild winter soil temperatures. Laboratory and field experiments were conducted to determine cold temperatures required to kill potato tubers in soil. Potato tubers in air dried soil columns exposed to decreasing temperatures typically supercooled to –3 to -7 C before exhibiting a distinct exotherm which stabilized at –1.4 to –1.5 C, representing the tuber freezing point. Tubers that were supercooled and removed from the cold environment before experiencing this exotherm were able to sprout and had no visual symptoms of freezing injury, whereas tubers that experienced the exotherm were unable to sprout. Tubers in soil columns hydrated to 7% SWC supercooled less than tubers in dry soil and exhibited an exotherm that stabilized near –1.9 C. Tubers exposed to temperatures near the tuber freezing point (-1.4 to –1.9 C) for periods of 1 min to 24 h, but not undergoing an exotherm, exhibited varying degrees of injury, which increased with time of exposure. Tubers held at –1.0 C for 4 to 24 h were unharmed and able to sprout similar to controls. In field trials conducted from 1993 to 1999 in the Columbia Basin of Washington, tubers buried at shallow depths (5 cm) were much more likely to experience lethal cold temperatures than tubers buried deeper. In general, when minimum soil temperature at tuber depth reached the critical range of -1.5 to -1.9 C or lower, tuber mortality occurred. Previous research reported freezing dynamics of potato tubers in air, whereas this is the first report of freezing behavior of potato tubers in soil. Monitoring of winter soil temperatures by depth in potato growing regions could be used to predict severity of volunteer potato for the subsequent growing season.