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Does the Minister agree with the statement made in a Facebook post by Environment Canterbury Councillor Ian Mackenzie that the reason for the Laghmor School drinking water supply exceeding the nitrate drinking water limit was the result of "excessive nitrogen fertiliser use on cropping farms back in the 80's and 90's", and that a high nitrate "plume" was identified "above and below Tinwald... over 20 years ago"?

Answered Question 36524 (2026)
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Asked by

Lan Pham

List MP · Green Party

Question

  • Does the Minister agree with the statement made in a Facebook post by Environment Canterbury Councillor Ian Mackenzie that the reason for the Laghmor School drinking water supply exceeding the nitrate drinking water limit was the result of "excessive nitrogen fertiliser use on cropping farms back in the 80's and 90's", and that a high nitrate "plume" was identified "above and below Tinwald... over 20 years ago"?

Answered by

Hon Nicola Grigg

Member for Selwyn · National Party · Minister for the Environment

Answer

I cannot say either way, because I have not received analysis on this matter. The causes of elevated nitrate concentrations in a particular groundwater supply depend on a range of factors, including land use history, hydrogeology, groundwater age and lag times. I have not received advice attributing the Laghmor School result to any specific activity or period. I expect nitrate pollution to reduce over time due to improved management practices, innovation, and clearer environmental limits.