Mitigation and best practice options
Here are some simple steps to minimise the effects of dairying on water quality and mahinga kai.
Reduce dairy effluent
Reduce the amount of wash down water used (e.g., pre-wetting the yard prior to milking is one technique used by farmers to speed up the wash down processes and reduce the amount of water needed). Also, the wash down process is more efficient if a high-flow, low pressure wash system is used.
Improve effluent storage and application
Oxidation ponds need to be the appropriate size to hold the quantities produced, and application to land must consider soil type, topography, and wet weather when the likelihood of runoff and leaching to groundwater increases. The weather, pasture growth, and application rate are critical factors in mitigating environmental effects.
Improve irrigation practices
Advice is available on management and maintenance of irrigation systems, including information about low application systems such as K-line. Farmers need to consider soil type, topography, and the risk of surface runoff leaching or flow into tile drains.
Fence waterways (including wetlands)
Fence off all areas adjacent to waterways to prevent stock access. Add fish friendly culverts and/or build bridges where stock are required to cross waterways.
Plant riparian vegetation
Many regional councils actively support farmers with planting guides and on-farm advice services and some provide plants at cost. For example, see Review of riparian buffer zone effectiveness (MAF technical paper, 2004).
Apply nutrient management
Employ a nutrient budget and use correct nutrient management practices to minimise losses to ground and surface water. Check out useful tools like 'OVERSEER' that disseminate information to farmers and promote correct nutrient management practices.
Improve stock and land management
Avoid overstocking to prevent soil pugging and compaction, even on well drained soils. Retire steep and eroded land. Provide either natural shade and/or shelter plantings for stock, which can reduce the pressure on vegetation situated closer to waterways. Divert road and track runoff away from streams to run overland instead of directly to streams, e.g., diverting runoff over rough areas of vegetation would improve infiltration of contaminants.
Best practice guidelines
Some specific recommended Best Management Practices (BMPs) for faecal pollution and nutrient management are listed below.
Faecal pollution management options could include:
- Fencing off all major waterways (i.e., stock exclusion from waterways and bridges for crossing).
- Diverting runoff from farm tracks entering streams to sediment traps or fields.
- Directing irrigation of dairy shed effluent to land (i.e., fewer pond discharges).
- Growing grass filtration strips in riparian strips.
- Avoiding grazing saturated soils in order to minimise runoff losses.
- Maximising soil infiltration by the use of standoff pads in wet conditions - which reduces overland flow.
Nutrient management options include:
- Irrigating dairy shed effluent to pasture (fewer pond discharges to waterways).
- Reducing soil phosphorous fertility to the economic optimum (adding enough fertiliser for productivity but not enough to create waste).
- Avoiding soil compaction caused by overstocking.
- Trapping particulate P with open-drain vegetation (grasses and riparian vegetation).
- Optimising farm nutrient inputs with nutrient budgeting.
- Applying nitrification inhibitors.
- Providing feed pad systems for wintering animals with effluent treated via oxidation ponds, thereby avoiding the deposition of urine and faecal matter (high in N) in paddocks during times when drainage is likely.
- Using natural and constructed wetlands for enhancing denitrification losses.
For more information about Best Management Practices
- Pathogen Pathways - Best management practices
- Best Management Practices for Feed Pad and Stand Off Pads
- Best Practice Dairy Catchment Study [PDF]
- Sustainable farming info from NZ Farm Environment Award Trust - Learning from Leaders Project
- McKergow, L.A.; Tanner, C.C.; Monaghan, R.M., Anderson, G. (2007). Stocktake of diffuse pollution attenuation tools for New Zealand pastoral farming systems.NIWA Client Report HAM2007-161 under subcontract to AgResearch for Pastoral 21 Research Consortium. 102 p.
- Tanner, C.C.; Sukias, J.P.S.; Yates, C. (2010). New Zealand guidelines for constructed wetland treatment of tile drainage. NIWA Information Series No. 75, Hamilton.
- Tanner, C.C.; Kloosterman, V.C. (1997). Guidelines for constructed wetland treatment of farm dairy wastewaters in New Zealand. NIWA Science and Technology Series No. 48, June 1997. 67 p.