EVELYN.THORN@cluthaleader.co.nz
Farmers were invited to discuss and understand the significance of contaminant losses and the effectiveness of good management practices for sheep winter grazing at a field day in Waitahuna recently.
The project and field day aimed to enable farmers to make evidence-based land management decisions for their own farms.
Now completed, the three-year research project on Ronald Alderton’s Waitahuna farm aimed to benchmark contaminant losses from sheep on winter crops and assess the impacts of retaining critical source areas in the grass in winter crop catchments.
The project’s research and findings were presented to nearly 30 farmers who attended the field day.
Two catchments were researched, where one year they were both sown in swede crop, the second year catchment A was sewn in grass and B sown in kale crop, then the third year the two catchments had vice versa.
Project managers said winter grazing was already known to make a significant contribution to total losses of contaminants transported from dairy farms to water.
However, very little information was available in losses when sheep were used to graze crops.
Project manager Craig Simpson said various evidence including nitrogen, phosphorus, suspected sediment and E.Coli were investigated and tested over the three years.
‘‘This project began in 2020, and we’re very pleased to be bringing the project full-circle now to farmers in the district,’’ Mr Simpson said.
AgResearch principal scientist Ross Monaghan, Chandra Ghimire, and Alison Rutherford, along with other key researchers, explained the findings in the research portrayed specific key take-home messages for farmers.
‘‘Grazing and treading pressures on the soil were low, allowing most of the rainfall to infiltrate. Contaminant losses reduced considerably compared to standard grazing practice, with phosphorus, sediment and E.colireductions of approximately 50%.
‘‘These combined effects meant that contaminant losses in surface runoff were low relative to those measured at other [cattle-grazed] sites.’’
Their main message was that protection of critical source areas (CSAs) from winter grazing could reduce fluxes of water contaminants and was proven to be very effective at reducing runoff of both sediment and other contaminants, and CSAs and ungrazed crop reduced the potential impacts of intensive winter grazing activities on water quality.
