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Oxygen Transport to Plant Roots
Author(s) -
Cook F. J.,
Knight J. H.
Publication year - 2003
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2003.2000
Subject(s) - radius , diffusion , porosity , flux (metallurgy) , microscale chemistry , aeration , oxygen , analytical chemistry (journal) , chemistry , thermodynamics , physics , mathematics , environmental chemistry , mathematics education , computer security , organic chemistry , computer science
A model that couples the diffusion of O 2 to plant roots at the microscale to diffusion of O 2 through the soil at the macroscale is derived. The solution is complex, but if the length scales ( Z r and Z m ; see APPENDIX for list of symbols) are equated a simple analytical expression can be obtained. This model is used to investigate relationship between a critical air‐filled porosity (θ m ) and the other parameters; viz temperature ( T ), O 2 concentration in the bulk soil ( C *), O 2 concentration at the root surface ( C r ), root length density ( L ), the ratio of root radius ( a ) to the water film radius ( R ), microbial respiration ( M o ), and length scales ( Z m and Z r ) related to the depth to which microbial and plant respiration are active in the model using sensitivity analysis. The model shows that θ m is not very sensitive to the O 2 concentration at the root surface ( C r ), or the ratio of root radius ( a )/water film radius ( R ), but is sensitive to all the other parameters in some part of their range. The results indicate that indices used to define soil aeration; O 2 diffusion rate (ODR) or O 2 flux, O 2 concentration, or air‐filled porosity, which have been previously used, are related and a single critical value for these is unlikely. If a constant critical value exists for one of these indexes it cannot exist for the other two. It is also shown that it is highly unlikely that a universal critical parameter related to soil aeration exists for any of these parameters. It is concluded that more parameters than ODR, O 2 concentration, or air‐filled porosity need to be measured if progress in soil aeration research is to be made.