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Shortterm temporal changes of soil carbon losses after tillage described by a firstorder decay model
 Author:
 La Scala, N., Lopes, A., Spokas, K., Bolonhezi, D., Archer, D.W., Reicosky, D.C.
 Source:
 Soil & tillage research 2008 v.99 no.1 pp. 108
 ISSN:
 01671987
 Subject:
 carbon dioxide, gas emissions, soil respiration, tillage, greenhouse gases, soilatmosphere interactions, carbon, losses from soil, prediction, models, soil organic matter, degradation, equations
 Abstract:
 Tillage stimulates soil carbon (C) losses by increasing aeration, changing temperature and moisture conditions, and thus favoring microbial decomposition. In addition, soil aggregate disruption by tillage exposes once protected organic matter to decomposition. We propose a model to explain carbon dioxide (CO₂) emission after tillage as a function of the notill emission plus a correction due to the tillage disturbance. The model assumes that C in the readily decomposable organic matter follows a firstorder reaction kinetics equation as: dC sail(t)/dt =kC soil(t) and that soil CCO₂ emission is proportional to the C decay rate in soil, where C soil(t) is the available labile soil C (gm⁻²) at any time (t). Emissions are modeled in terms soil C available to decomposition in the tilled and nontilled plots, and a relationship is derived between notill (F NT) and tilled (F T) fluxes, which is: F T = a 1 F NT e  a 2 t , where t is time after tillage. Predicted and observed fluxes showed good agreement based on determination coefficient (R ²), index of agreement and model efficiency, with R ² as high as 0.97. The two parameters included in the model are related to the difference between the decay constant (k factor) of tilled and notill plots (a ₂) and also to the amount of labile carbon added to the readily decomposable soil organic matter due to tillage (a ₁). These two parameters were estimated in the model ranging from 1.27 and 2.60 (a ₁) and 1.52x10⁻² and 2.2x10⁻² day⁻¹ (a ₂). The advantage is that temporal variability of tillageinduced emissions can be described by only one analytical function that includes the notill emission plus an exponential term modulated by tillage and environmentally dependent parameters.
 Agid:
 21947
 Handle:
 10113/21947

http://dx.doi.org/10.1016/j.still.2008.01.006