See more from this Session: General Soil Physics: II (Includes Graduate Student Competition)
Monday, October 17, 2011
Henry Gonzalez Convention Center, Hall C, Street Level
The influence of land use on soil structure should be quantified because land use has important influences on soil physical and soil hydraulic properties that are strongly related to soil structure. This work characterizes soil properties related to soil water and gas transport processes in two land use systems, pasture and cropland. In a research site (4125 m2) with cropland and pasture use, a total of 60 sampling points were laid out along four transects. Soil water content was measured using a capacitance probe for 10-cm vertical depth increments down to 1 m depth. Sixty undisturbed soil cores (356.5 cm3) from a depth of 4-10 cm were taken from both land use zones for gas diffusion, air filled porosity, and bulk density measurements. Oxygen diffusivity at -333 cm matric potential was measured using a gas chamber and a gas chromatograph. A photo acoustic environmental gas monitor (INNOVA Model 1412) was used to measure CO2 and N2O fluxes in the field. All soil measurements revealed different soil structural properties in the pasture site and the cropped site. Pasture soil had lower bulk density than cropped soil. Cropped soil had higher surface soil water content and higher profile water storage. Surface water content and water storage in the cropped site both revealed spatially structured variation. Relative oxygen diffusivity was higher in the pasture soil indicating that soil structure was more developed and with a more conducive pore system than the cropped site. Higher CO2 and N2O flux occurred in the pasture indicating that pasture soil is a more biologically active and permeable soil than cropped soil.