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  • Rights: The University of Waikato Te Whare Wānanga o Waikato and Waikato Regional Council
    Published 12 March 2020 Referencing Hub media

    Bryan Hart is Senior Crop Manager for AS Wilcox & Sons. Bryan explains the techniques his company uses to stop soil erosion and make the most efficient use of irrigated water.

    Question for discussion:

    • How do contour oat strips in the potato fields work like riparian strips next to streams and rivers?



    Our business is a fourth-generation family business. In order for us to be here for another four generations, we want to do the right thing, and our customers obviously expect it. It’s really a matter of using as many tools in the toolbox as you can get.

    So we start with our process for applying for a consent for water, and that’s based on how much water will the plants need each day. That governs the maximum we can take on a daily basis. And then we’re scheduling that. We do weekly soil/water measurements using a device called a neutron probe, and that tells us exactly how much water deficit we have in the soil. So we’re scheduling our water based on crop demand, the evapotranspiration and that daily limit for that particular consent.

    We have different delivery devices – either gun and reel or centre pivot – and in terms of the time when we put it on, evening is more efficient water use than during the day. If it’s really, really windy, we won’t irrigate because of course the delivery is not accurate. And trying to apply it to the crop at the growth stage that’s going to give us the most return for that particular crop.

    There’s a number of processes, which we do to ensure that we are actually stopping that soil and water leaving the farm. The way we try to manage this slope here is when we plant it, immediately after we come through with a ripper and do what we call wheel track ripping, and you can see here how the soil has been pulled off back in May when this crop was first planted. And it’s created a drain channel down through here at the bottom of the row, and the idea there is it’s actually allowing the water to infiltrate right where it lands when it rains. So it reduces any risk of the water accelerating, running off down the row.

    Waikato Regional Council and Auckland Regional Council co-funded research with the local growers looking at protection of the environment in the growing area and silt management and erosion controls. And some of that information is what we’ve developed today to include things like the oat strips.

    Behind us you’ll be able to see a contour strip of oats, which we do about every 30 to 50 metres depending on the slope. It’s closer when it’s steeper and further apart when it’s flatter. And the idea there is if any water does move down the row, it acts like a natural living barrier, if you like, dropping out any particles rather than carrying them to the end of the row into the drain beyond. In some rows, we actually have oats growing in the drain as well. So as those oats grow up, they suck up moisture whilst we wait for the potatoes to actually close the row over. We’re really trying to keep the soil, the water and the fertiliser – all the things that we need to grow these plants – where it originally was.

    Increasingly, you know we do see some fairly significant storms and weather events. And so whilst we’re trying to manage everything in field, we have to have quite large preventative mechanisms to avoid discharge into public roads or into streams or rivers, and so silt ponds, bunded traps in drains and things like that. Actually letting our drains grow very weedy is also another good mechanism that we’ve done.

    The ledger is positive, but certainly there are extra costs involved with contour oat strips and things like that. There is loss of crop area and it’s extra operational activities, but the benefits of course are protecting the soil and avoiding run-off and making a place for the beneficial species, so we hope that those sorts of things are positive overall in the balance.


    Bryan Hart
    Keith Watson
    AS Wilcox & Sons Limited
    Alice Trevelyan
    Waikato Regional Council
    Footage of potato and carrot harvesting, irrigator and potato pack house, AS Wilcox & Sons Limited.


    This video has been developed in partnership with the Waikato Regional Council as part of the Rivers and Us resource.

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