Abstract:
Pre-harvest foliar desiccation of Yellow Globe Danvers onions was
investigated as a means to improve harvest procedure and to reduce
storage losses. Foliar desiccation tended to increase storage disease
and sprouting incidence versus the untreated controls. Paraquat
approximately doubled storage disease in both years. Stoddard solvent
and ethephon increased disease in lesser amounts. Endothall at 1.1 kg
a.i./ha gave disease results equal to the control. Root sprouting increased
with most treatments but not to such a degree as to compromise
commercial value. Neck moisture was efficiently lowered by most desiccant
treatments but the final neck moistures achieved by the treatments
did not correlate with subsequent disease or sprouting. Phenolic concentration
in neck tissue was studied for several treatments and a weak
negative correlation was found with subsequent disease in storage. Bulb
size did not appear to be affected by the desiccant treatments. A study
of mineral redistribution in untreated bulbs during the top senescence
process in the month preceding harvest showed that nitrogen declined in
neck tissue by 50% and in leaf tissue by 25%. Phosporus and zinc also
declined in both tissues by 50% or more. Potassium declined in leaf
tissue by ca. 50% but showed a 25% accumulation in neck tissue. Calcium
and boron more than doubled in neck tissue and increased at a slightly
lower rate in leaf tissue. Copper increased ca. 50% in both organs.
Iron and aluminum showed a strongly correlated accumulation pattern
in both tissues, accumulating at rates in excess of 500%. Magnesium
and manganese showed no consistent change in concentration.
