Nkongolo, Nsalambi (Lincoln Univ. Center of Excellence GIS Lab, 820 Chestnut Street, Jefferson City, MO, 65102; Phone: 573-681-5397; Fax: 573-681-5154; Email: nkongolo@lincolnu.edu)

Soil Thermal Properties and CO₂, CH₄ and N₂O Fluxes in a Corn Field

N. V. Nkongolo *, N. Nkongolo, K. Schmidt

Soil thermal properties can affect the production and escape of greenhouse gases from soils to the atmosphere. We studied the relationship between CO₂, CH₄and N₂O fluxes and soil thermal conductivity (K), resistivity (R) and diffusivity (D) in a corn field at Lincoln University Freeman Farm, from May to December 2004. The experimental field was divided into four plots of 0.25ha each. Each plot received the same rate of PK (60-80 lb.ha^-1)and either 0, 60, 120 or 180lb.ha^-1lb of N. Six chambers were installed in each plot. Soil samples were collected for analysis of chemical and physical properties. Soil air samples for determinations of CO₂, CH₄ and N₂O were collected from static and vented chambers of 0.30 m long and 0.20 m diameter installed in the field in May 2003 shortly after corn emergence. The sampling process consisted in closing the chamber two ventilation holes with rubber stoppers, putting the chamber greased circular top, vacuuming the chamber then allowing it to be filled with air from soil for 20 minutes, collecting an air sample 4 times with a 50 ml syringe and storing it in a 200ml Tedlar bag. The chamber top had a middle hole covered by a stopper and used for air vacuuming and sampling. Thermal properties were measured at 0.06 m depth inside each chamber using KD2 Thermal properties meter. Analysis of CO₂, CH₄ and N₂O from air samples was done within two hours of sampling at Dickinson Research Center with a Shimadzu Greenhouse Gas GC-14. Results obtained showed that for the entire field, CO₂ fluxes ranged from 5.56 to 395.61 mg C-CO₂ m^-2 h^-1, CH₄ uptake from 5.39 to 89.22 ug C-CH₄ m^-2 h^-1 and N₂O fluxes from 10.69 to 181.86 ug N-N₂O m^-2 h^-1. Except for CH₄ uptake which only correlated with K, CO₂ and N₂O fluxes were also linearly correlated with R and D with coefficient of correlation (r) ranging from 0.40 to 0.60. In addition, CO₂, N₂O and CH₄all correlated among themselves with (r) ranging from 0.40 to 0.90. However, when data for each plot was analyzed individually, the linear relationship between gas fluxes and thermal properties was significant only in the plot receiving 180 lb.ha^-1N. In this plot, K and R linearly correlated with CH₄ and N₂O with (r) ranging from 0.80 to 0.90. The correlation between CO₂, N₂O and CH₄ also persisted, but was restricted to only CO₂ and N₂O in other plots. The results suggest that soil thermal properties may be important controlling factors for greenhouse gas fluxes from soils.