Articles
ZINC DEFICIENCY AND CORRECTION IN CALIFORNIA PLUM ORCHARDS
Article number
985_23
Pages
189 – 192
Language
English
Abstract
Zinc deficiency is a common problem in California plum (Prunus salicina) orchards.
We have conducted extensive research to understand the situation and develop effective ways to correct the problem.
Using large sand tanks in the field, we have induced severe zinc deficiency on Fortune plum trees grafted to Nemaguard rootstock.
Yield and fruit quality were greatly reduced and mid-summer leaf samples had zinc levels as low as 4 to 6 ppm.
We have concluded that the currently recommended deficiency threshold of 18 ppm is too high and should be around 10 or 12 ppm, although there is a lot of variability between 12 and 18 ppm.
Leaves testing at 20 ppm and higher are definitely within the sufficiency range.
We have also developed a fall or dormant shoot sampling protocol that can supplement the standard summer leaf sampling procedure.
Fall foliar applications of zinc sulfate are the most cost effective method of supplying some zinc to the trees under Californian conditions.
However, this still only provides temporary correction and annual applications often seem to be needed.
Mixing an insoluble form of zinc (such as zinc oxide) into the soil of a planting hole prior to planting provides a substantial boost in leaf zinc concentrations that lasts for several years.
We have conducted extensive research to understand the situation and develop effective ways to correct the problem.
Using large sand tanks in the field, we have induced severe zinc deficiency on Fortune plum trees grafted to Nemaguard rootstock.
Yield and fruit quality were greatly reduced and mid-summer leaf samples had zinc levels as low as 4 to 6 ppm.
We have concluded that the currently recommended deficiency threshold of 18 ppm is too high and should be around 10 or 12 ppm, although there is a lot of variability between 12 and 18 ppm.
Leaves testing at 20 ppm and higher are definitely within the sufficiency range.
We have also developed a fall or dormant shoot sampling protocol that can supplement the standard summer leaf sampling procedure.
Fall foliar applications of zinc sulfate are the most cost effective method of supplying some zinc to the trees under Californian conditions.
However, this still only provides temporary correction and annual applications often seem to be needed.
Mixing an insoluble form of zinc (such as zinc oxide) into the soil of a planting hole prior to planting provides a substantial boost in leaf zinc concentrations that lasts for several years.
Authors
R.S. Johnson, K.R. Day
Keywords
Prunus salicina, zinc sampling, zinc formulations, foliar zinc applications, uptake efficiency, deficiency threshold
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