Surface dressings
Trace elements have restricted downward movement if applied to the surface of most soils. Therefore, they are best incorporated into the soil prior to planting, particularly in areas with a history of trace element deficiencies. Chelates are said to be more mobile in soil than sulphates.
Heavy applications of lime may restrict availability of trace elements if the soil pH is adjusted above pH 7 (CaCl2 extract). Soil pH testing is essential to assist in decisions on the need for, and rate of, lime prior to application.
Deep banding, or incorporation as close to the tree line as possible without major root damage occurring, may be the best approach where trace element deficiencies are detected in established trees. This should be kept to a depth of 10 to 15 centimetres for minimal root disruption.
Applications in late winter or early spring are recommended. Surface applications of zinc oxide, or zinc sulphate (through the irrigation), were not found to be effective in correcting zinc deficiency in mature apple trees. Both products, therefore, should be ripped into the rootzone to have any chance of supplying zinc to the trees. A combination of both soil and foliar applications should be applied at rates and times expressed in this publication, in an attempt to correct zinc deficiency.
Copper: Apply copper sulphate at rates from 250g per tree depending on tree size. The dressings should be spread out around the tree within a 1.5–2m radius from tree butts. Normally best applied in early August and incorporated into the soil where possible.
Magnesium: Apply magnesium sulphate (Epsom salts) at rates from 500g for young trees to 2kg for large trees, as for copper sulphate, or in a strip for hedgerow plantings.
Zinc and manganese: Apply pre-plant where possible at depth. Use superphosphate pre-plant blend below. Zinc and manganese may be applied separately, or in combination, at the rate of 3kg of manganese sulphate and 2kg of zinc oxide per 100m of tree row (half these amounts per 100m of band on each side of the trees).