Tuesday, November 14, 2006 - 10:05 AM

Soil Carbon Dioxide Fluxes in Relation to Physical Properties as Influenced by Management Practices.

Jay Jabro1, Upendra Sainju2, Bart Stevens2, and Robert Evans2. (1) NPARL ARS-USDA, 1500 N. Central Ave, Sidney, MT 59270, (2) NPARL USDA-ARS, 1500 N. Central Ave, Sidney, MT 59270

Carbon dioxide (CO2) flux from the soil surface can be influenced by soil physical properties due to changes in management practices. The CO2 flux, soil temperature (Ts), soil water content (θv), soil bulk density (ρb), and air-filled porosity (Ea) were measured every 1 to 2 wk in no-till (NT) and conventional till (CT) malt barely and undisturbed grass-alfalfa (UGA) systems in a Lihen sandy loam soil (sandy, mixed, frigid Entic Haplustoll) under irrigated and non-irrigated conditions in western North Dakota. Soil Ea was calculated from total soil porosity and qv measurements. Significant differences in CO2 fluxes between management systems were observed in some measurement dates. Higher CO2 fluxes were noted especially in till compared with no-till treatment immediately after a heavy rain or irrigation. A negative correlation between CO2 flux and Ea (r = – 0.24, P ≤ 0.01) indicated inverse relationship, while positive correlation was found between CO2 flux and Ts (r = 0.61, P ≤ 0.01). Using stepwise regression analysis, a significant relationship between CO2 flux and θv, Ts, Ea (CO2 flux = –1.47 +6.29θv+ 0.06Ts – 1.6 Ea; R2 = 0.50, P ≤ 0.01) was observed. Soil CO2 flux could be a function of soil temperature, water content, and air-filled porosity due to changes in soil and crop management practices.