Management effects on soil carbon storage in New Zealand pastures

Abstract

The amount of soil carbon is the net effect of carbon inputs and decomposition and is influenced by many factors including the level of herbage utilisation, root production, litter quality, soil fertility and soil moisture status. Long term experiments at Winchmore, in mid- Canterbury, show soil carbon levels increased after initial development, but after 50 years fertiliser input has had no net effect on soil carbon, while increasing the frequency of irrigation has actually resulted in lower soil carbon levels. Pasture development at Ballantrae , in the southern Hawke's Bay, has been associated with a decline in soil C levels, with the high fertility treatment having only slightly higher soil C than the treatment receiving a lower rate of fertiliser. At Tara Hills, in South Island semi-arid high country, increased stocking rate is associated with a decrease in soil C. Contrary to common perceptions increases in pasture and farm productivity do not necessarily result in increased soil carbon storage. Keywords: carbon, fer tiliser, grazing management, irrigation, soil organic matter