Managing Cull Potatoes

Despite rain delays, harvest is nearly complete in the region, and it is a time of year when cull potatoes accumulate. If not properly managed, these waste potatoes can be a source of potato pathogens, insects, and weeds, as well as other undesirable consequences such as odors from decomposing piles.

In addition, some states require timely disposal of cull potatoes to avoid nuisance problems and to protect newly planted crops the following growing season. University of Idaho extension personnel have recently published an updated bulletin (available online at https://www.uidaho.edu/extension/publications/publication-detail?id=cis0814) to address how to effectively dispose of cull potatoes.

The bulletin details six options for managing cull potatoes, including winter field spreading, burial, use as livestock feed, compost, and chemical applications. Now is the time to consider and prepare for most of these options. If handled properly and spread over a field (no more than two layers of potatoes deep), winter freezing can render the tubers non-viable. Tubers spread across a field also serve as a source of nutrients for the following crop (Table 1).

If the window for field spreading is missed, burial is another option that can be implemented any time of year. A key tip is to alternate layers of potatoes with layers of soil to facilitate tuber breakdown.

Cull potatoes can also be used as livestock feed. Not only are potatoes rich in minerals (Table 1) but they are an excellent source of energy (Table 2). The advantages and potential risks of using potatoes for feed are further detailed in the bulletin. 

Cull potatoes can also make excellent compost, if done correctly. Guidance for successful composting of cull potatoes can also be found in the bulletin.

Chemical options to ensure cull potatoes do not produce foliage include herbicides labeled for non-crop uses (Table 3.). Although no herbicides are capable of completely killing a tuber, they may control sprouting. Desiccant products are also available, including those used for vine kill. More information on available products is available in the bulletin. As with any chemical application, read and follow label instructions when using herbicides to manage a cull pile.

Monitoring the cull pile in early spring may be needed to ensure it is nonviable. Generally, potatoes die after 24 hours at 28 degrees F or 12 hours at 25 degrees F. Naturally, the deeper and wider the cull pile, the greater the likelihood that some of the cull potatoes will still be able to sprout in the spring. For more detailed information on managing cull and waster potatoes, read the complete bulletin available online at https://www.uidaho.edu/extension/publications/publication-detail?id=cis0814