Irrigated dairying can increase soil carbon
Gabriel Moinet setting up equipment at the study site (John Hunt).
Almost half of New Zealand’s greenhouse gas emissions come from pastoral agriculture. Any intensification of agriculture could increase our greenhouse gas liability under international agreements.
Environmentally sustainable production systems are needed to control pollution and support New Zealand’s ‘clean and green’ brand. In a 3-year project on a commercial irrigated dairy farm in Canterbury, we measured the efficiency of water use and changes in soil carbon. Neighbouring irrigated and a dryland pastures were compared. On both pastures we measured CO2 exchange continuously in situ (also CH4 and N2O), dry matter production, water use, precipitation and evaporation, pasture consumption and all management activities to construct a complete carbon budget.
The first year’s carbon results indicate the irrigated, intensively-managed pasture system gained more carbon than was removed by grazing, producing twice as much biomass as the dryland pasture, and water use efficiency increased by over 30%. Results suggest farm management decisions (e.g. irrigation and grazing) can be tuned to enhance dry matter production, water use efficiency and soil carbon all at the same time.