As nitrogen (N) management comes increasingly to the fore in New Zealand land use regulations, agricultural researchers have been investigating pasture and forage options that may help farmers mitigate N leaching.

 

As nitrogen (N) management comes increasingly to the fore in New Zealand land use regulations, agricultural researchers have been investigating pasture and forage options that may help farmers mitigate N leaching.
If these options do prove useful, says Agriseeds Pasture Systems Manager Graham Kerr, the plan is to build them into ‘Overseer’ software which models nutrient status on individual farms.
“The pastoral industry needs to measure and mitigate nitrogen leaching; this is what the NZ public is demanding, and we must have forage options for this. We don’t want to be forced into using barns or structures that may greatly reduce NZ’s competitive advantage of having animals graze pasture.”

 

Among options being studied are:

• Winter active pastures – “There is evidence that more winter active pastures take up more N through winter, which is the period of most N leaching on many farms. For example Italian ryegrass would be better than perennial ryegrass, which in turn is better than chicory or lucerne,” Graham says.
• Lower N crops – There is also evidence that winter crops with a lower protein content will be environmentally better. For example fodder beet could be better than kale.
• Deeper rooting pastures – “The view here is that plants with increased rooting depth will better take up soil N and lessen leaching. Different pasture species, or breeding for deeper rooting may be outcomes.”
• Different species – For example, some evidence has shown including chicory and plantain into a perennial ryegrass/white clover based pasture is decreasing N concentration in urine. Work on this is continuing, Graham says. Some plants
• produce condensed tannins (e.g. sulla and birdsfoot trefoil) which can potentially reduce N leaching. But there are limitations in adaptability of these plant species in farm systems.

 

Another area of research is ryegrasses with higher water soluble carbohydrate, which include all tetraploid ryegrasses, and a number of perennial ryegrasses including those marketed under ‘high sugar’ brand.
“To date there is little evidence they will have much effect in NZ pastoral systems. More data will be published this coming year.”
The next few years will bring significant change in N leaching and mitigation, Graham says. Regulation, through regional council management plans, is either in place or will exist shortly. Farmers will need to estimate losses on their farms. Caps on N leaching will become standard.
“Part of future farming systems will be how to operate profitably within these N caps, and tools that help mitigate N leaching will be an important part of NZ’s sustainable farming future.
“Significant research is going into pasture and plants, to look at how best to integrate them in farm systems to mitigate N leaching – watch this space. In the long term we are looking to breed new plants that better fit environmental objectives.”