KEY POINTS:
New Zealand scientists trialling "high sugar" ryegrasses bred in Britain say they can boost dairy production in autumn and reduce the amount of nitrogen leached from cow urine.
The grasses contain more water-soluble carbohydrates than standard perennial ryegrasses.
Phil Ulrich, Research agency Dairy Insight investment's manager, said high sugar grasses were expected to perform better in colder, southern regions than in warmer, northern regions.
The trials showed promising results in reducing the nitrogen excretion by cows, a huge problem for degradation of freshwater, and for greenhouse gas emissions of nitrous oxide.
"Initial blood and milk sample analyses indicate a lower level of surplus nitrogen that would ultimately be excreted by the cow as urinary-nitrogen, when compared with standard ryegrass," he said.
Nitrogen loss to waterways as nitrates and to the atmosphere as nitrous oxide are key environmental issues for the dairy industry.
Dairy farmer lobbyists have claimed there is little opportunity for mitigation of nitrous oxide emissions in the short term, though some environmentalists have said widespread uptake by dairy farmers of a "nitrification inhibitor" chemical being sold by fertiliser companies could slash the industry's loss of nitrous oxide to the atmosphere.
"With lower levels of excess nitrogen to be excreted by cows, high sugar grasses have the potential to contribute to that target" said Mr Urlich.
Further trials by Agresearch at Palmerston North will investigate the effect of including high sugar grasses in mixed pastures that contain white clover and why in the second autumn the high sugar grasses produced 10 per cent more milksolids.
- NZPA
