Horticulture Sector To Investigate Impact Of Tile Drains On Water Quality

A new project in the Hawke’s Bay is investigating the impacts of tile drains on horticultural land, to provide valuable information about their effect on freshwater quality.

Horticultural tile drains are used to divert excess moisture from the soil. This can help waterlogged land become more productive. This project seeks to understand whether this diversion of water contributes additional nutrients to our waterways that may impact water quality.

The Ministry for Primary Industries (MPI), several key players in the horticulture industry, and Hawke’s Bay Regional Council have kicked off a project to investigate this further. MPI is contributing $1.34 million towards the project through its Sustainable Food and Fibre Futures (SFF Futures) fund.

“It’s a big knowledge gap currently and a potential issue that the sector is keen to examine proactively,” says Leander Archer, Horticulture and Environment Consultant at AgFirst Consultants Ltd, which is leading the research.

“The horticulture sector wants to ensure that its nutrient use is efficient, and understand if the tile drains are in fact impacting our waterways. If there’s no impact then great, we’ll have the data to prove it, and if there’s an impact at certain times of year or when we face certain types of weather, we want to know about it so we can change our management strategies.”

The project will collect data over three years on 16 commercial properties in the Heretaunga Plains in Hawke’s Bay that are used for growing fruit and vegetables. It will set up two trial sites on each farm, enabling experimentation with new management strategies in year three on one site, while leaving the other as a control.

“The Heretaunga Plains has been selected because it has extensive tile drainage networks and a range of groundwater pressures and soil types, and much of the catchment is used for high-value horticulture. Plus, the Karamū catchment within this area has reported water quality issues,” says Ms Archer.

“Horticulturalists want to grow healthy food that contributes to healthy communities, in a way that cares for the soil and waterways that sustain us all. This research will help them to do that. If you don’t measure it, you can’t manage it.”

Steve Penno, MPI’s director of investment programmes, says the outcomes of this research have the potential to provide deeper insights into how the horticultural industry can become more sustainable.

“We all want clean waterways,” says Mr Penno. “The findings will be useful for other regions across the country as well. At the very least we’ll gain more information about whether this is a problem we need to address. And at the most we’ll identify the size of the issue and how to best measure nutrient losses to understand how to mitigate these.”

AgFirst Consultants HB Ltd is currently concluding the site selection process for the trial farms, for monitoring to begin in Spring. Interested growers are encouraged to follow the project through their industry body or can get in touch at hawkesbay@agfirst.co.nz.

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