Abstract

Regulations that place a limit on the amount of nitrate-nitrogen leaching from agricultural land are currently being developed by Regional Councils throughout New Zealand. These regulations may require substantial reductions in nitrate leaching from current typical dairy farm levels. Notions of the pasture plant ‘ideotype’, which have previously emphasised pasture growth and the intake of digestible nutrients, should now also include characteristics which can reduce the nitrogen surplus in the animal, and, therefore, the amount of nitrogen (N) excreted in urine. Information on the critical external or internal N requirements of candidate pasture species could be used to develop hypotheses regarding future grazed forage systems; currently, there are few data available for this purpose. Recent empirical evidence indicates that diverse pastures incorporating forage herbs such as chicory and plantain can reduce total urinary N load while maintaining similar levels of herbage accumulation to ryegrass-white clover pasture. However, insufficient information is available to identify the mechanisms through which the urinary N reductions occur. This specific knowledge gap needs to be filled. In addition, more information is needed on the general nitrogen nutrition physiology of candidate pasture species for future forage systems.

DF, Chapman, GR Edwards, and JB Pinxterhuis

Proceedings of the New Zealand Society of Animal Production, Volume 74, Napier, 102-107, 2014