The calculations come from herd improvement company CRV Ambreed, which has determined the daily numbers using existing information related to milk urea concentration in daily bulk milk reports.
CRV head of research and development Phil Beatson estimated the national dairy herd was excreting 1000 tonnes of nitrogen each day, of which 20% was leached through soils and ultimately ended up in ground water.
If too much nitrogen entered waterways it could cause aquatic weeds and algae to grow too fast, reducing oxygen and harming aquatic life.
``This is an issue we must address now to safeguard future generations of New Zealanders,'' he said.
He believed the most the effective way to deal with the nitrogen leaching issues was to reduce the amount of nitrogen hitting the ground - and that would mean changes in the way we breed and feed cows.
