Mitigation practices to enhance soil carbon and reduce nitrous oxide at the paddock scale

Nitrous oxide emissions and soil carbon stocks can both be strongly influenced by plant traits, management practices, soil properties and climate. NZAGRC research is looking at the impact of plantain and maize management practices on environmental outcomes.

Current projects

Project title Lead organisation/s
Mitigation practices to enhance soil carbon and reduce nitrous oxide at the paddock scale Waikato University

Overview

There is evidence that plantain reduces nitrous oxide emissions (see also the Low-emitting plants project page in the Nitrous Oxide part of this website). However, we do not yet know the implications for soil carbon stock changes during the establishment and maintenance phases. Moving to low-nitrogen feeds such as maize can reduce nitrous oxide emissions but cropping in general results in losses of soil carbon. The NZAGRC has set up a project dedicated to exploring these issues by addressing the following research questions:

  • Does the inclusion of plantain into a mixed species ryegrass/clover sward increase soil carbon and decrease nitrous oxide emissions? How do greenhouse gas emissions vary seasonally as the proportion of plants in swards vary?
  • What are the changes in soil carbon and nitrous oxide emissions through the establishment phase when converting conventional swards to include Plantain or other forage crops?
  • What are the impacts of different management scenarios (e.g. Plantain content, grazing timing etc) and climate on annual and seasonal nitrous oxide emissions and soil carbon stocks?
  • What is the rate of recovery of soil carbon stocks after pasture has been re-established on a maize production site and what is an appropriate return period for growing maize to maintain soil carbon stocks?

The project aims to test and validate management options that avoid trade-offs where the net reduction of one greenhouse gas results in increased emissions of another. Trade-offs with production and productivity will also be considered. Integration of measurements and modelling will be used to investigate the efficacy of feed production systems (grazed pasture and supplemental feed) based on plant traits to maintain or increase soil carbon stocks and reduce nitrous oxide emissions at the paddock scale. While the work focuses specifically on plantain and maize, the generalised measurement approach developed will be transferable to testing other species and management options within grazing/forage systems.

The project will take field measurements of carbon dioxide exchange, net carbon balances and nitrous oxide emissions from different pasture swards at Troughton Farm in the Waikato and Ashley Dene in Canterbury, using eddy-covariance approaches.