Nitrate leaching forecast to increase
Southland farmers are being told that nitrate leaching could significantly increase as a result of the changing climate.
A report, prepared by Manaaki Whenua Landcare Research for the Deep South National Science Challenge and released yesterday, says leaching in the region might be higher and more variable with climate change.
The report’s lead author, Anne-Gaelle Ausseil, said the researchers were surprised that extreme weather events were projected to have such a strong impact on nitrogen leaching.
‘‘Because these modelling results were unexpectedly high, and were only modelled in one location in Southland, this needs further investigation across the region and for different farm types,’’ Ausseil said.
Annual leaching in Southland was modelled to increase significantly because of ‘‘more spring rain and more frequent extreme rainfall events’’, the report says.
Nitrogen is a key nutrient used to grow grass on farms, but when there is more in the soil than plants can use it is at risk of leaching into groundwater or runs off into rivers and streams, where it degrades water quality.
Southland Federated Farmers president Geoffrey Young said there was nothing ‘‘too concerning’’ in the report. ‘‘Farmers are used to adapting,’’ he said.
‘‘There’s no doubt we need to consider more water storage in terms of dams.’’
Manaaki Whenua is a Crown research institute based in Lincoln, Canterbury. The report used case studies in Hawke’s Bay, Southland and Waikato.
Other implications for Southland primary industry operators included a more pronounced risk of severe heat stress for animals.
‘‘Heat stress will be an increased risk for animal health, with about two additional weeks of risk for moderate heat stress by the 2090s,’’ the report says.
Ausseil said the study looked at the impact of overall climate trends, but was not able to calculate the impact of all risks.
‘‘Extreme events like hailstorms and damage from insects are also likely to increase under climate change conditions, but it is difficult to quantify the additional measures needed to respond to these events.
‘‘We hope this research will further encourage long-term strategic adaptation such as diversifying cultivars, shifting sowing dates and planning additional shade and shelter.’’