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Tips on Potato Storage Management

Posted: September 5, 2012

Placing problem potatoes into storage can't make them better, but properly managed storage can help maintain quality and minimize deterioration of good quality potatoes.

Managing storage includes making sure your storage has proper ventilation and temperatures and no condensation problems. Other concerns are sprouting, pressure bruise potential, sugar development, and disease problems.

Unless there is a need to dry out wet or rotting potatoes, always humidify ventilating air. To help avoid condensation, make sure the ventilating air is slightly cooler than tubers at the bottom of the pile. Free water on potatoes will initiate or accelerate water rot problems in tubers.

Since uniform air distribution within the storage is needed for maintaining tuber quality, eliminate as much dirt and debris as possible as the potatoes are being placed in storage. Remember, however, that excess ventilating air can lead to tuber dehydration and increased shrinkage. This can result in lost tonnage and decreased tuber quality. To minimize tuber weight loss and reduce the chances of having pressure bruise in your potatoes, maintenance of proper ventilation, temperature and humidity are important. Humidity levels should be above 90 percent and preferably at 95 percent or more.

To determine if your storage will properly keep potatoes, check out this brief list of overall basics of storage management.

Facility Preparation

•    Repair all insulation materials to minimize the potential for condensation.
•    Clean plenum and duct ports thoroughly.
•    Replace worn humidity equipment and high-pressure nozzles.
•    Check for corrosion on all surfaces that may limit the life of the storage facility.
•    Service the air system and check all fans for proper balance.
•    Check the air delivery system by adjusting all ports or ducts for optimum and consistent airflow.
•    Repair or replace worn components on air louvers, both fresh air and exhaust.
•    Calibrate all computerized sensors that are used for control functions.
•    Service the relative humidity supply systems -- check for mineral deposits and eliminate clogged flow paths.
•    Operate your storage for conditioning before the potato crop is delivered.
•    Know the quality of the incoming potatoes and the potential problems that might arise in storage. Protecting the quality of the stored tubers is the goal of all storage management.

During Potato Delivery

•    Tape all duct seams to improve system performance -- open seams will reduce air delivery consistency.
•    Harvesting and handling operations should deliver a minimum of 75 percent bruise-free potatoes for both short- and long-term storage.
•    Check pulp temperatures of potatoes going into storage -- ideal temperature range is a minimum of 48oF to a maximum of 60o F. Suspend harvest operations, whenever possible, until pulp temperatures in the field are in this temperature range.
•    Limit potato pile height to 16 to 18 feet to minimize pressure bruise. Remember that pressure bruise can be variety dependent.
•    Operate fan and humidity systems as soon as the first ducts are covered. This early operation helps to remove pulp temperature differences between fields, truckloads and time of day. 
•    Clod and debris removal from the incoming loads is important to achieve optimum air circulation performance in the pile from the ventilation system.
•    Fill each storage facility with potatoes destined for similar end uses.
•    Close storages as soon as filled to rapidly achieve temperature equilibration of the pile.
•    Maintain pulp temperatures at 50 to 55o F for two to three weeks for proper wound healing. Relative humidity of 95 percent is always recommended for wound-healing period and for continued short- or long-term storage.
•    Reduce pile temperatures slowly, approximately 2 to 3oF per week, to a holding temperature of 45 to 48oF for processing, 42 to 45oF for fresh pack, 50 to 52oF for chipping stock.
•    Continue to monitor the storage daily for operational continuity and for any potato problem that might occur. Air circulation times should be set to maintain the pile temperature less than 2oF difference from bottom to top.  Continuous fan operation at reduced airflow or speed is capable of maintaining the desired temperature control of the pile while reducing energy costs of fan operation.
•    Sprout control should be done by certified applicators. The type of inhibitor or time of application may vary with different varieties.

During Unloading 

Maintain storage air supply during storage unloading to minimize quality losses. Remember that good storage management during the unloading operation includes adjustment of duct airflow to maintain consistent supply to all parts of the remaining pile.

Bill Lamont, Penn State Department of Plant Science, wlamont@psu.edu

(The article was taken from Bill Bohl, Extension Educator's newsletter, The Spudvine, and was written by Nora Olsen and Gale Kleinkopf from the University of Idaho.)