Optimizing Foliar Potassium Use in Table Grape Vineyards
Commodity Protection and Quality
2013 Annual Report
1a.Objectives (from AD-416):
The primarily objective is to examine the interaction of vineyard treatments of foliar potassium, ethephon, abscisic acid and irrigation regimens on color development and quality of table grapes.
1b.Approach (from AD-416):
Three factorial split plot vineyard experiments examining the effect of plant growth regulator interactions with foliar potassium applications are proposed: ‘Flame Seedless’ in two experiments (Coachella Valley and San Joaquin Valley) and ‘Crimson Seedless’ in one experiment (San Joaquin Valley). The incidence of summer bunch rot disease and postharvest decay will be recorded, as will the quality of the fruit will be documented before harvest, the day of harvest, and after long storage.
This agreement supports Objective 1 of the parent project, Evaluate pre-harvest practices and treatments for table grapes using substances of minimal environmental and dietary risk. The interaction of vineyard treatments of foliar potassium, ethephon, abscisic acid and irrigation regimens on color development and quality of table grapes was examined in two experiments, one in the San Joaquin Valley and a second in the Coachella Valley near Indio, California. In both tests, foliar potassium applications enabled earlier harvest because it increased sugar content and accelerated berry color development. This treatment was additive in action with other irrigation deficit and ethephon applications, both of which increased berry color to facilitate early harvest, but potassium applications did not improve when combined with abscisic acid. A secondary benefit of early harvest is a reduced incidence of fungal decay before and after harvest, since the period that the berries remain in the vineyard, where they are vulnerable to diseases and insects, is shortened.