The winter treatment of grapevines with zinc and its interaction with time of pruning

Abstract

Field experiments on dormant Sultana vines showed that yields were increased by applying zinc sulphate solutions immediately after pruning. Treatment by the swabbing of pruning cuts gave similar results to a cover spray. Increasing the concentration of zinc sulphate (up to the maximum tested-35 per cent) increased yield and no bud injury was seen. A delay of a day or more between pruning and treatment drastically reduced its effectiveness. Shorter intervals were tested but the results fluctuated ; a possible reason for this is discussed. The movement of zinc along Sultana canes was gauged by analysis of sections of cane cut up at varying times after swabbing the pruned end. In one year zinc moved at least 20 inches within two days, whereas, in another, it moved only 10 inches after one month. The yield of Grenache vines was increased when pruning was delayed from early winter until late winter and early spring. Zinc treatment increased yields in vines pruned in June, July, and August, but depressed yields when applied to vines pruned in September.