Copper Accumulation in Vineyard Soils in New Zealand

Abstract

The main purposes of this research are to establish the extent and character of copper spray use in the viticulture industry in New Zealand; and to determine the level of copper accumulation nationally and in the main viticultural regions. The research also included pilot investigations of the storage of copper on different soil fractions and changes in nutrient status of vineyard soils with high copper concentrations. A questionnaire survey was completed by 124 growers from throughout the country. Copper sprays are still used in the majority of cases, but have either never been used or are no longer used in almost 30% of vineyards covered in the survey. Where copper is used, the load being applied to the vines each year varies widely, but the impression is that most growers are moderate in their use of copper. There are geographical patterns in use, and there is some evidence that newer vineyards, often in drier areas, are applying lower rates of copper, and less frequently. The maximum soil copper concentration recorded was 304 mg kg−1, with several samples in the range 150–260 mg kg−1. However, most of the sample concentrations were less than 75 mg kg−1. Of the 43 vineyards sampled, 36 showed significant elevation of total soil copper compared to the respective control concentrations. The other seven vineyard were low, or nil, users of copper. Most of the vineyards in the sample had a mean total soil copper concentration below 50 mg kg−1, but two vineyards were over 100 mg kg−1, and two more higher than 70 mg kg−1. The results showed that total soil copper in a vineyards is related to the number of years such sprays have been used, but there was no evidence of a link to basic soil properties. Overall, copper contamination of vineyard soils in New Zealand appears to be lower than levels reported from vineyards in other countries. However, there are grounds for monitoring soil copper levels more closely in all vineyards established more than about 40 years ago, especially in the more humid regions, and especially if they were planted on sites previously used for orcharding. The current trend to use less copper is welcome from the point of view of soil management, but vigilance will still be required, even under low use regimes.