Cleaning up greenhouse waste

4 December 2006

A programme is under way to encourage greenhouse growers in northwest Auckland to correctly dispose of waste liquid fertilisers. This will see a specialist in greenhouse nutrient solution management visit around 150 growers in the region to encourage them to dispose of waste in an environmentally sound manner.

Glenys Kroon, the Auckland Regional Council’s (ARC) Manager Rural Compliance, says greenhouse growers who do not correctly dispose of nitrate-rich waste liquid fertilisers may put the environment at risk by polluting waterways, contaminating ground and drinking water, and causing excessive weed growth near their greenhouses.

“New Zealand is working hard to reduce the amount of nitrates in our waterways and ground water. Good inroads have been made by the pastoral farming industry. There are a lot of glasshouses in Auckland so attention is now being focussed on encouraging local greenhouse growers to better manage their waste disposal.”

The ARC has contracted Monica Xu, a final year Masters student whose specific research area is greenhouse nutrient solution disposal, to visit all greenhouse growers in west and north Auckland over the summer months to discuss their disposal methods. Where necessary, she will advise growers how to dispose of waste nutrient solution in a more environmentally friendly manner. Ms Xu is fluent in English, Mandarin and Cantonese, which maybe helpful in communicating with some members of this community.

Every grower’s situation is unique and there is a huge variation in greenhouse operations’ size and use of technology, which means that it is impossible to take a ‘one size fits all’ approach.

As a result, Ms Xu will work with growers individually and suggest options that best suit their situations.

“We are not telling growers how to run their operations. Rather, we want to ensure they know about the range of liquid fertiliser disposal options that are available and understand which one/s best suit their needs and the requirements of the Resource Management Act,” says Ms Kroon.

Advice given to growers includes:

- Recycling the nutrient solution will significantly reduce the solution discharge frequency and quantity.

- Using rain rather than other water sources supports the recycling of nutrient solution because rainwater is more pure and decreases the likelihood of excessive mineral and salt build-ups.

- Using high quality growing media will reduce run-off by enabling plants to more efficiently use water.

- Reduce run-off by better monitoring the amount of water being used and cutting back where possible.

- Maintaining good greenhouse system hygiene will reduce the rate and level of contaminant build-up.

- The best option for nutrient solution disposal is to reuse it as fertiliser to irrigate crops with high nitrogen uptake rates (e.g. silage or hay).

- Never discharge greenhouse nutrient solution into waterways.

ENDS

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