Whitehead D, Schipper LA, Pronger J, Moinet G, Mudge P, Calvelo Pereira R, Kirschbaum M, McNally S, Beare M, Camps Arbestain M, 2018. Management practices to reduce losses or increase soil carbon stocks in temperate grazed grasslands in New Zealand.  Presentation to the 2018 Agriculture Greenhouse Gas Inventory Conference, Wellington March 2018.

The presentation will summarise the findings from the manuscript that has been approved and submitted to a journal

The 4 per 1000 Initiative: Soils for Food Security and Climate was launched in December 2107 to promote voluntary action by countries to achieve the aspirational target of annually increasing soil carbon storage by 4‰ (0.4%). We undertook a review to identify opportunities for management practices that could be adopted to reduce losses or increase gains of soil carbon stocks on New Zealand’s temperate grasslands, where grasslands occupy 56% of the land area.

While labile carbon is the source of most of the heterotrophic respiration, the bulk of soil carbon stocks comprise stabilised carbon, protected from decomposition by the formation of organo-mineral complexes. For New Zealand grassland systems with moderate to high soil carbon stocks, the carbon saturation deficit in many of the soils may be low, making increases in soil carbon stocks difficult to achieve. Model simulations have shown that the goal of increasing both soil carbon and milk production could be achieved best by increasing carbon inputs from supplementary cattle feed. We review the limited findings from field studies for a range of management practices including the addition of fertilisers, feed imports, applications of manure and effluent, irrigation, sward renewal with minimum tillage, reduced grazing intensity, the addition of biochar, full inversion tillage and the introduction of earthworms and dung beetles. We conclude with a list of recommended criteria that could be adopted to assess the success and suitability of management options to increase soil carbon stocks. We identify priority research questions that need to be addressed using experimental approaches that require ongoing field measurements.
