Reducing chemical leaching and run-off

AS Wilcox & Sons use a variety of techniques to minimise pesticide and fertiliser use when growing potatoes. Senior Crop Manager Bryan Hart explains some of them.

Jargon alert: Bryan talks about New Zealand GAP. GAP is an acronym for good agricultural practice. NZGAP certification provides assurance that fruit and vegetables grown in New Zealand are safe and sustainably produced.

Question for discussion:

• Why do you think European supermarket chains would be interested in water quality tests done in New Zealand?

Transcript

BRYAN HART

We start with the customer, and we’ve got some really discerning customers which demand our water be tested each year. So we have to do a series of tests as part of our New Zealand GAP accreditation. If we’re sending onions to Europe and that sort of thing, some of the big supermarket chains there want to see the results of those water tests.

We’re obviously testing our product rigorously for residues. We’re only using products that are registered for use on those crops. So as long as you’re working within those frameworks, then you’re maintaining a reasonably low level of chemical input. In terms of stopping them polluting, it’s applying them in the safe manner, ensuring that wind speeds and things like that are not strong so you’re not blowing over the fence, special technology on the nozzles of the sprayers to avoid things like spray drift, keeping the water in your farm.

The fertiliser programme that we work on is what we call a nutrient budget. And so that starts by accurate soil testing across the field, factoring in the return from the last crop and then designing a fertiliser strategy for that crop. With potatoes, we have special technology to place the fertiliser immediately at the seed piece in the mould. So it’s not broadcast over the soil, we place it at the plant at the time of planting. For example in our spring crop, we’re using slow-release fertiliser because obviously a lot of rainfall through the winter and the spring months, and so we actually want to just slowly release that nitrogen to the crop during that long growth phase, so that’s ensuring that the crop can meet its demand without sudden rushes of leaching.

A beneficial programme to us is an integrated pest management programme, or IPM, where you have a combination of the crop, the timing and the scheduling of the crop. And then you’re looking at the predator insects that attack the pest species that you’re concerned about. So we have entomologists that inspect our crops weekly and crop scouts that check to see what pests or diseases are present. And based on that, we then decide whether or not we have to apply a chemical or not.

The good thing about using the good beneficial programme is that they are working for you 24/7. If you look at the example of our oat strips, aphids, which are normally a pest, will move into the oats, and then lacewings and some of the other predators, they’ll move in and attack the aphids. And so once they’ve established themselves there with a food source, they can then move out of there into the potato crop and target the tuber moth and potato psyllid, which are more concerning for us as a major pest in our potato crops. And in some of our crops like our early spring potato crops, we can very often get through to Christmas without having to apply any insecticides on those crops at all

Acknowledgements

Bryan Hart
AS Wilcox & Sons Limited
Footage of men talking around potato bin, red onion harvesting, potato pack house and men in potato field, AS Wilcox & Sons Limited