Abstract:
Studies addressed impacts of planting dates and variable N applications on numbers
and size of Russet Burbank stems and stolon nodal position in relation to tuber growth and levels of hollow heart (HH) and brown center (BC). Low preplant N regimes produced larger tubers and final yields, and less HH and BC than the high N regime. Reduced preplant N regimes also lowered tuber grade and specific gravity. Negative effects of the low preplant N regime were offset by delaying planting or beginning application of post-BC initiation N earlier. Stem size influenced plants season-long and affected tuber size and yield, early- and late-season HHBC development, and HHBC dissipation and severity. These responses were related more to stem and tuber growth than to weather. Levels of HHBC increased as similar-sized tubers grew. Tubers expressed less
HHBC, regardless of size or stolon nodal position, when growing at different rates or
times than most other tubers. HHBC development began, declined, and increased at
different times during the season. Tuber susceptibility to HHIBC increased throughout the season in association with increased stem size and/or reduced stems per plant. Plants with 3 or more stems produced higher tuber yields but less HHBC than plants with fewer than 3 stems. Large-stem tubers from 1- and 2-stem plants grew faster and were more susceptible to HHBC than large-stem tubers on plants with 3 or more stems.
Delayed plantings reduced HHBC and increased stem numbers per plant, thereby reducing the proportion of high yielding, HHBC susceptible stem-types. Delayed plantings did not affect the growth stage(s) during which tubers became susceptible. Preplant N regime did not affect stem numbers per plant, but HHBC was reduced by low regimes. Low preplant N plants exhibited equal or increased tuber growth rates, but reduced vine biomass compared to high preplant N plants; consequently, large stems, especially from single- and double-stem plants, showed more BC dissipation, resulting in less early-season HHBC compared to high preplant N plants. Late-season HFIBC was less affected by N treatment.
