Long-term changes in soil carbon in pastures

sites_a4map_3In collaboration with Manaaki Whenua – Landcare Research we have been analysing re-sampled soil profiles from grazed pasture around New Zealand. We demonstrated large losses of total C and N from Allophanic and Gley Soils on flat land. Other soil orders had no detectable change in soil C or N. Conversely, pastures on hill country were gaining carbon.

Using this information, we contributed to designing a soil carbon monitoring system for New Zealand that will sample 500 statistically selected sites nationwide. Supported by Manaaki Whenua – Landcare Research and the Ministry of Primary Industries.

Schipper, L.A.; Parfitt, R.L.; Ross, C.; Baisden, W.T; Claydon J.J.; Fraser S. (2010) Gains and losses in C and N stocks of New Zealand pasture soils depend on land use. Agriculture Ecosystems and Environment. 139: 611–617.

Schipper, L.A.; Parfitt, R.L.; Fraser, S.; Littler R.A.; Baisden, T.W.; Ross, C. (2014) Soil order and grazing management effects on changes in soil C and N in New Zealand pastures.  Agriculture Ecosystems and Environment. 184: 67-75.

We are trying to determine why this carbon has changed with a number of hypothesis being tested – including the role of cow urine in solubilising soil organic matter:

Lambie, S.M.; Schipper, L.A.; Balks, M.R.; Baisden, W.T. (2012) Solubilisation of soil carbon following treatment with cow urine under laboratory conditions. Soil Research. 50: 50–57.

Gains on hill country may be due to recovery of topsoil following wide-spread erosion when land was cleared from native forests some ~100 years ago:

Parfitt, R.L.; Baisden, W.T.; Ross, C.; Rosser, B.J.; Schipper, L.A.; Barry B. (2013) Influence of erosion and deposition on carbon and nitrogen accumulation in resampled steepland soils under pasture in New Zealand. Geoderma. 192:154-159.