Effects of long-term inputs of fertiliser and irrigation on soil carbon under grazed pasture

Abstract

Soils constitute the largest pool of terrestrial carbon, and the development and adoption of methods designed to increase storage of carbon is an effective means of reducing atmospheric carbon dioxide. The main objective of this research project was to assess the effects of long-term irrigation and fertiliser inputs on carbon in stony soils developed under intensively grazed pasture in New Zealand. Replicated field trials were established at Winchmore in 1949-1952 to assess the input requirements of pasture under flood irrigation, and are the longest running of their type in New Zealand. Results revealed that despite substantial increases in pasture production in response to inputs of fertiliser and irrigation over 60 years, there was no significant sequestration of organic carbon in the soil profile to 1m, and soil profile carbon actually decreased with increased irrigation.