Grapevine Response to Concentrate and to Dilute Application of Two Zinc Compounds

Abstract

Vineyard trials were conducted in 1975 and 1976 to compare the effectiveness of two zinc foliar spray compounds and two methods of application in correcting zinc deficiency. Zinc-EDTA chelate (14.2% Zn) and basic zinc sulfate (50% Zn) were compared with dilute (1169 liters/hectare) and concentrate (234 liters/ hectare) spray applications in two Thompson Seedless vineyards.

Grapevine foliar uptake of and response to zinc applications were measured by shoot-tip analysis and berry size and degrees Brix measurements. Dilute application was more effective than concentrate application, regardless of the zinc compound used. This was shown in higher shoot-tip zinc levels 10 and 14 days after application and in higher berry weights and lower degrees Brix at harvest. The zinc chelate was more effective in foliar zinc uptake (10-and 14-day shoot-tip zinc levels) than basic zinc sulfate when compared at an equal application rate of elemental zinc per hectare. However, on a commercial recommended rate basis, basic zinc sulfate at 2.24 kg zinc/ha was more effective than the zinc chelate at .56 kg zinc/ha. It is concluded that zinc deficiency can be corrected most effectively with dilute (full-wetting) application of basic zinc sulfate if foliar sprays are used.