Getting the best out of hump-and-hollow farming
NIWA is working with the New Zealand Landcare Trust on a project looking at ways to minimise nutrient runoff from West Coast land conversions.
Farmers around Lake Brunner often create a series of long ridges and valleys (humps and hollows) across their fields to cope with high rainfall and improve drainage. There is, however, a public perception that intensification of farming and land conversion by humping and hollowing are increasing the nutrient runoff into the iconic lake.
The project aims to:
- assess the hydrological regime and nutrient load from land converted by humping and hollowing
- provide practical solutions for mitigating nutrient runoff
- work with farmers to assess the social and economic costs and benefits of humping and hollowing
Last month, we presented our first year results for hydrology and water quality at three sites on a humped-and-hollowed farm in Rotomanu, near Lake Brunner. The hydrology is dominated by frequent large floods due to the frequent and intense rainfall. The area received 3677 mm of rain for 8 March 2004 to 28 February 2005. Nutrient concentrations varied a lot over time, but we noticed significant peaks shortly after fertiliser was applied, even when it did not rain. We are now working to quantify how much fertiliser is lost, what the crucial timeframe is, and how these factors are affected by the presence and intensity of rainfall. So far, the study also suggests that hollows lined with wetland plants may reduce nutrient runoff.
Meanwhile, interviews with farmers, conducted in association with the NZ Landcare Trust, have also been analysed. These covered such questions as the benefits and costs of humping-and-hollowing, possible environmental effects, and solutions.
The study sites are generously provided by Dave and Aiga Marley. The project is funded by MAF’s Sustainable Farming Fund, with contributions from West Coast Regional Council, Westland Milk Products, Department of Conservation, NZ Landcare Trust, and NIWA. It is due to be completed by June next year.