Soil carbon dynamics: The effects of nitrogen input, intake demand and off-take by animals

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 a...

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Bibliographic Details
Published in:The Science of the total environment 2013-11, Vol.465, p.205-215
Main Authors: Parsons, A.J., Thornley, J.H.M., Newton, P.C.D., Rasmussen, S., Rowarth, J.S.
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Biochemistry and biology
Biological and medical sciences
Chemical, physicochemical, biochemical and biological properties
Dry stock
Environment
Fundamental and applied biological sciences. Psychology
Hurley pasture model
Lactating stock
Longevity
Physics, chemistry, biochemistry and biology of agricultural and forest soils
Sequestration
Soil science
Zoology (interactions between soil fauna and agricultural or forest soils)
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Summary: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. ► We identify key drivers of soil C change in temperate managed grassland. ► Stocking rate has a major effect in reducing soil C sequestration potential. ► Soil C loss under lactating cows is a result of N, not C, being removed in milk. ► At the same intake demand, N loss under milk is less than under dry-stock. ► Food production, N loss and C sequestration cannot be maximised at the same time.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2013.02.019