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Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling
Published on: January 16, 2014
Soil carbon dynamics: the effects of nitrogen input, intake demand and off-take by animals
A J Parsons1, J H M Thornley, P C D Newton
1Institute of Agriculture and Environment, Massey University, PB 11001, Palmerston North, 4021, New Zealand.
Abstract:
Elucidation of the drivers of soil carbon (C) change is required to enable decisions to be made on how to achieve soil C sequestration. Interactions between different components in the ecosystem in combination with feedback mechanisms mean that identifying drivers through conventional experimental approaches or by retro-fitting models to data are unlikely to result in the insights needed for the future. This paper explains soil C dynamics by using a process-based model. Drivers considered in the model include nitrogen (N) fertiliser inputs, intake demand, and off-take of animal products. The effect of the grazing animal in uncoupling the C and N cycles is explained, plus the implications of the farming system ('drystock' versus milk). The model enables depiction of the dynamic equilibrium achieved with time when a proposed change in the drivers is sustained. The results show that soil C loss under lactating cows is a result of N, rather than C, being removed in milk. Counter-intuitively, at the same intake demand, N loss under 'milk' is less than under 'dry-stock', as is C loss in animal respiration. Possibilities for changing the longevity of C in the soil are discussed, and the compromise between food production, N loss and C sequestration is considered.
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