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Water quality impacts of crash grazing a hill country wetland
This research project allowed two crash grazing events to examine the effect on phosphorus, nitrogen and sediment loss from the seepage wetland.
Why is it important?
Wetlands often form in the bottoms of valleys, creating a green oasis for stock during dry periods. However treading damage and urine and dung deposits can increase the risk of sediment and nutrient loss.
If these areas are fenced from stock, crash grazing (high stocking rates over a short period of time) is a technique for limiting stock access to short, set periods to control weeds. However investigation of its impact on nutrient and sediment loss is limited.
How was it conducted?
To study the impact of crash grazing on phosphorus, nitrogen and sediment loss from a seepage wetland, two crash grazing events were conducted with sheep for a period of four hours each – in February and June 2014.
Crash grazing had no discernible effect on nitrate, ammonium or dissolved reactive phosphorus concentrations, with concentrations mostly below the limit of detection. However there was a noticeable difference in sustained sediment levels and total nitrogen concentrations leaving the wetland after a crash grazing event.
There was also a distinct difference between the longevity of sediment in summer and winter. Total nitrogen and phosphorus concentrations in winter become negligible quite quickly post the event, however in summer they remain elevated for at least two hours after a crash grazing event.
Page authorised by General Manager, Massey Farms
Last updated on Tuesday 16 August 2016
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