Potato quality: V. Relation of time of planting, time of harvest, and fertilizer treatment to composition and cooking quality

Smooth Rural potatoes subjected to 10 different fertilizer treatments were planted at three different dates and potatoes of each of these treatments were harvested on three different dates. Thus, tubers were obtained which were of different degrees of maturity and which during the latter portion of their growing period had been subjected to different light and temperature conditions. Tubers were used for specific gravity measurements, dry weight determinations, and cooking tests for determination of color and texture differences. Tubers at the first harvest from the first planting were consistently higher in specific gravity and dry weight than those from the second and third plantings. The time of planting had no consistent effects on the occurrence of blackening. The more mature tubers were of a more mealy texture than those planted later and less mature. The specific gravity of tubers of the second and third plantings at the first harvest is consistently lower than those of the same dates of planting at the second and third harvests. Similar differences appear in dry weight of tubers of the three harvests. The time of harvest had a marked effect on color and texture of boiled tubers. The later harvested tubers blackened to a greater extent and had a higher texture rating than those harvested early. Relatively small differences exist in specific gravity and dry weight of tubers grown with the various fertilizer treatments. Differences in degree and extent of darkening which occurred were related to the effect of the fertilizer on hastening or retarding maturity. The average weight per tuber as well as the number of tubers in each specific gravity group increased steadily from the low range to a maximum at the medium range and then declined at the high specific gravity range. A relationship exists between temperature and light conditions during the latter part of the growing season and the specific gravity, dry weight, color, and texture of boiled tubers grown under those conditions.