Natural seepage wetlands: can they reduce nitrogen losses?
They may be generally disliked by farmers and thought of as troublesome ‘bogs’,
but seepage wetlands have proven highly effective at preventing contaminants from
reaching waterways. These so-called ‘kidneys of the land’ could serve as one useful
tool in the dairy sector’s efforts to reduce nitrate leaching.
View Resourcebut seepage wetlands have proven highly effective at preventing contaminants from
reaching waterways. These so-called ‘kidneys of the land’ could serve as one useful
tool in the dairy sector’s efforts to reduce nitrate leaching.
Link provided with permission.
Characterisation and potential optimisation of seepage wetlands for nitrate mitigation in New Zealand hill country
A thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science, Massey University, School of Agriculture and Environment, Palmerston North, New Zealand
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Nitrate removal in riparian wetlands: interactions between surface flow and soils
A New Zealand study found that riparian wetlands with springs can still remove significant nitrate despite fast-flowing water. Tracer experiments showed that vertical mixing between surface water and saturated soils enhanced denitrification, with about a quarter of nitrate removed over just 1.5 metres. This suggests such wetlands have greater nitrate removal potential than previously assumed.
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Denitrification capacity of hill country wet and dry area soils as influenced by dissolved organic carbon concentration and chemistry
A New Zealand study found that seepage wetlands in hill-country farms have a far greater capacity to remove nitrate than surrounding dry soils. Wetland soils contained much higher levels of dissolved organic carbon, which supported stronger denitrification activity—up to 69 times higher than dry areas. These findings highlight the vital role of seepage wetlands in improving water quality across pastoral landscapes.
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Hill country wetland hydrological characterisation for nitrate attenuation
A study of a hill-country wetland near Palmerston North found that nitrate attenuation is strongly influenced by hydrology and rainfall patterns. The wetland was sometimes a net source of nitrate and sediment under high winter rainfall, but acted as a nitrate sink under evenly distributed rainfall. Shallow groundwater was mostly oxic and low in nitrate, with limited subsurface nitrate reduction. These results highlight that surface flow and the subsurface redox environment largely control nitrate removal, providing guidance for enhancing wetland nitrate mitigation in pastoral landscapes.
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