Key Production Stages: Plant Senescence to Harvest
The two facets of this stage are vine and tuber maturation. It begins with vines showing the first signs of dying, yellowing of leaf tissue, until harvest. In early-season varieties, this covers from 14 to 18 weeks after planting (11 to 15 weeks after emergence). For later varieties, this stage can come later and last longer.
Most Critical Actions = vine desiccation.
Key Biological Activities = vine death and tuber maturity.
Production Practices:
Little, if any, irrigation is needed during this stage; the soil moisture should be held between 60 and 65% field capacity, mostly to avoid clumping for easier harvest. No fertilization should be applied; it may delay vine maturation and make desiccation more difficult.
The main practice in this stage is the use of desiccation techniques to hasten vine death. These can be chemical, mechanical or a combination of the two. The main purposes of desiccation are to promote tuber maturity, ease harvesting and minimize tuber infection by blight spores on the vines.
Plant Development:
From senescence to death, the leaves and branches turn yellow to brown and the leaves fall off.
From senescence to death to harvest, the tubers mature; their growth ends. Dry matter, especially starch, reaches a peak and the reducing sugars, specifically glucose, fructose and sucrose, decrease to a low. The tuber skin hardens and thickens. These changes are promoted by vine death. Chemical vine desiccants are used to achieve complete and yet gradual (two to three weeks) death of vines. If death is too rapid either by desiccation methods or frost than the tubers do not mature as well and may develop internal defects.
Key Production Stages