ARS | Publication request: Estimation of CO2 diffusion coefficient at 0-10 cm depth in undisturbed and tilled soils

Submitted to: Archives of Agronomy and Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 22, 2010
Publication Date: January 1, 2012
Citation: Jabro, J.D., Sainju, U.M., Stevens, W.B., Evans, R.G. 2012. Estimation of CO2 diffusion coefficient at 0-10 cm depth in undisturbed and tilled soils. Archives of Agronomy and Soil Science . 58(1): 1-9.

Interpretive Summary: The CO2 diffusion coefficients (D) at 0 – 10 cm layer in no-till (NT), and conventional till (CT) malt barley and undisturbed soil grass-alfalfa (UGA) soils were estimated using Penman, Millington-Quirk, Ridgwell et al., Troeh et al., and Moldrup et al. models. Both soil air-filled porosity (') and estimated CO2 diffusivity (D) were significantly affected by tillage at the 0.05 probability level. The average diffusion coefficients of CO2 through the 0- 10 cm soil layer estimated by the five models were in the range of 0.003288 to 0.01093 for NT, 0.003974 to 0.01181 for CT, and 0.003283 to 0.01055 m2 h'1 for UGA. Soil ' in the 0 – 10 cm surface layer decreased from 0.2723 in the CT to 0.2536 in the NT and 0.2476 m3 m'3 in UGA, corresponding to 9.1 and 11.4 % decreases in the diffusion coefficients of CO2 through NT and UGA soils, respectively. The relationship between the ratio of the CO2 diffusion coefficient in the soil to free air, D/D0, and ' were well described by a power (R2=0.985) function. The model (Eq. 12) is useful for predicting CO2 gas diffusion coefficients in undisturbed and tilled soils at various air-filled porosities where gas diffusion coefficient measurements are not feasible. The advantage of using such a predictive model arises from the fact that actual measurements of CO2 gas diffusion coefficient in soils are time consuming, costly and difficult to conduct.

Technical Abstract: Diffusion coefficients (D) of CO2 at 0 – 10 cm layers in undisturbed and tilled soil conditions were estimated using Penman, Millington-Quirk, Ridgwell et al. (1999), Troeh et al., and Moldrup et al. models. Soil bulk density and volumetric soil water content ('v) at 0 – 10 cm were measured on April 14, June 2, and July 12, 2005 at 0 – 10 cm depth in no-till (NT) and conventional till (CT) malt barley and undisturbed soil grass-alfalfa (UGA) systems. Air-filled porosity (') was calculated from total soil porosity and 'v measurements. Both soil air porosity and estimated CO2 diffusivity at the 0 ' 10 cm depth were significantly affected by tillage. Results of CO2 diffusion coefficients in the soil followed trends similar to those of soil ' data. The CT tended to have significantly greater estimated soil CO2 diffusion coefficients than the NT and UGA treatments. The relationship between D/D0, and air-filled porosity was well described by a power (R2 = 0.985) function. The model is useful for predicting CO2 gas diffusion coefficients in undisturbed and tilled soils at various ranges of ' where actual gas D measurements are time consuming, costly, and infeasible.