15N as an indicator of N cycling

With AgResearch and GNS Science, we investigated whether 15N content of soils can be used as an indicator of previous N cycling in pastures. If correct we may be able to use 15N as a indicator of the future sensitively of pasture systems to nitrogen losses. This work was conducted by Paul Mudge as the focus of his PhD.

Flood irrigation at the long-term Winchmore trial.

Paul has sampled and analysed soil samples from several long-term fertiliser trials including archived samples from Winchmore irrigation and fertiliser trials and Ballantrae phosphorus and nitrogen trials.   He has also looked at samples from chronosequences of forest conversion to pastures.

This work was funded by MSI through a subcontract from GNS Science. Collaborators were Troy Baisden (GNS Science) and Anwar Ghani (formally AgResearch).

Mudge, P.L.; Schipper, L.A.; Baisden, W.T.; Ghani, A.; Lewis, R.W. (2014) Changes in soil C, N and δ15N along three forest-to-pasture chronosequences in New Zealand. Soil Research. 52: 27–37.

Mudge, P.L.; Schipper, L.A.; Ghani, A.; Upsdell, M.; Baisden, W.T. (2013) Changes in Natural 15N Abundance in Pastoral Soils Receiving Differing Amounts of Superphosphate Fertilizer and Irrigation for 50 Years. Soil Science Society of America Journal. 77, 830–841.