Management and Markets
Pages in tuber aging section:
In storage, the major factor that progresses tubers through the stages of aging is temperature which can be manipulated to produce the desired age of tubers at planting (Schrage, 1999b). Planting older seed of cultivars that tend to oversize such as Yukon Gold may have advantages to improve uniformity increasing the number marketable sizes especially for early markets (Asiedu et al., 2003). This may also be true for seed production where a smaller tuber size profile might be preferred. Some cultivars are not benefitted by aging such as R Norkotah while others might such as Yukon Gold and Shepody. To age seed, store at 38F then before planting store for 2 to 6 weeks at 55-60F. To hold young seed, store at 38F and warm to 45F just before cutting and plant in soil about the same temperature as the tubers. Cutting tubers breaks apical dominance between eyes releasing eyes to sprout. De-sprouting may result in more stems and smaller tubers as this eliminates apical dominance.
Because young seed emerges slower, there is a greater chance of seed decay and cankers (stem and stolon). Planting young seed in warmer soil can hasten its sprout emergence and growth. Do not plant seed right out of cold storage into soil as this will promote condensation of the seed and increase decay. Warm seed to 50-60F for a few days and plant in soil slightly cooler. This will add some physiological age to the seed tuber or pieces. Seed planted in light sandy soil which warms rapidly tend to produce more stems, set more tubers and result is smaller harvested tubers. Extra N starter can partially overcome the effects associated with aging that is N can partially mimic young seed characteristics. Note that later planting tends to produce more stems per plant and have lower yield.
Sprouting of tubers under light produces short, tough, green sprouts. Green sprouting or chitting enhances emergence, tuber formation, vine size, and earlier maturation as much as two weeks. It is used for early harvested yields. Light requirement is low and stacking trays are often used. Chitted tubers are planted with cups not picks to avoid sprout damage.
When a longer growing season is possible and large tubers are marketable such as bakers and French fryers, young seed just about to produce a few sprouts may be desired. On the other hand, for an early fresh market, older seed at the multiple sprout stage may be more desirable to get a higher yield early and a quicker vine senescence. Older seed might be more desirable for seed production where a smaller tuber profile at harvest may be more desired than bulk yield. To decide what is the optimal physiological age to plant, one must take into consideration the cultivar’s characteristics, the market for the crop and the anticipated conditions during the growing season.
References:
Asiedu, S.K., Astatkie, T. and Yiridoe, E.K. 2003. The effect of seed-tuber physiological age and cultivar on early potato production. J Agron & Crop Sci 189:176-184.
Schrage, W. 1999. Keeping notes with respect to physiological age. In Seed Potato Management. Univ Minnesota. (www.mnseedpotato.org/extension/article).