Dairy farms and water quality

​Here are the key points from the Parliamentary Commissioner for the Environment's Update Report on water quality in New Zealand (published in June 2015).

Here's the full report: http://www.pce.parliament.nz/assets/Uploads/Update-report-Water-quality-in-New-Zealand-web.pdf

• Productivity (milk solids per hectare) continues to increase rapidly in the dairy sector, largely driven by the use of more inputs – water, fertiliser and supplementary feed.
  
  
• There has been a great deal of action to mitigate nutrient losses on dairy farms, especially on the management of shed effluent, bridging waterways and fencing waterways. As at May 2014 nearly 24,000 kilometres of waterways had been fenced.
  
  
• Keeping stock out of wetlands and the provision of nutrient management data has been much slower to occur.
  
  
• Standard mitigation techniques such as applying shed effluent as fertiliser on land, keeping stock out of waterways, and riparian planting all help reduce nitrogen losses, but are more effective at keeping phosphorous (and pathogens and sediment) out of waterways.
  
  
• The two nutrients – nitrogen and phosphorous – differ in a number of important ways, with nitrogen being the greater water quality challenge.
  
  
• Experiments on research farms have shown that it is possible to reduce nitrogen losses by as much as 50%, but the most effective techniques are generally expensive.
  
  
• On the Future farmlet in Waikato, nutrient losses were reduced by 40 to 50% by using less nitrogen fertiliser, a lower stocking rate, with cows that excrete less nitrogen in their urine and are taken off pasture for defined periods – however, profitability fell by 5%.
  
  
• The main source of nitrogen is animal urine. But it is not just how much urine animals produce that matters, but how they urinate. Sheep urinate in small amounts, so the grass is able to take up much of the nitrogen as fertiliser. Cows, on the other hand, gush litres of urine at a time, overwhelming the ability of the grass to absorb it. Because the nitrogen exists in highly soluble chemical forms, some of the surplus is washed off by rain, but most leaches through soil into groundwater.
  
  
• The intensification of dairy farming – more milk from each cow and more cows on each hectare – has been enabled by using more nitrogen fertiliser, irrigation in some regions of the country, and by supplementing grass with palm kernel extract and other stock food. The increase in nitrogen concentrations in waterways is sometimes attributed to the rapid increase in the amount of nitrogen fertiliser used. But it is not nitrogen fertiliser per se that has caused the problem. Rather, it is what it has enabled – a longer grass growing season, and thus, more cows and more urine.
  
  
• The volatility of milk prices is leading some to question the high input model that has become increasingly prevalent on New Zealand farms. DairyNZ principal scientist John Roche recently told a forum of farmers that the average dairy farmer is milking a hundred more cows than a decade ago, yet making no more money. Dr Roche believes that the greater use of supplementary feed is undermining the resilience of the system, and that changing the model would reduce nitrate leaching.
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• The report concludes that "high stocking rates that rely on importing feed not only lead to high nutrient losses, but also carry greater financial risk. It is encouraging to see the focus on ever-increasing production being questioned, and some win-win strategic thinking occurring."