Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2010
Publication Date: 6/17/2010
Citation: Jabro, J.D., Stevens, W.B., Evans, R.G., Iversen, W.M. 2010. Spatial Variability and Correlation of Selected Soil Properties in the AP Horizon of the CRP Grassland. Applied Engineering in Agriculture. 26(3):419-428.
Interpretive Summary: The spatial variation of water content (WC), total porosity (TP), penetration resistance (PR), saturated hydraulic conductivity (Ks), ECe, and pH at the 0 ' 25 cm depth of the A horizon of a sandy loam soil within a field of CRP grassland was explored and assessed using classical and geostatistical methods. Results from both statistical approaches indicated that small to moderate spatial variability existed across the field for soil properties considered in this study. Cross-semivariograms exhibited a strong negative spatial interdependence between soil PR and WC, TP, and Ks. Both the mean difference error (MDE) and the mean square error (MSE) showed that co-kriging did not improve predictions for PR with WC, TP, and Ks than kriging. Thus, kriging is considered to be an accurate and adequate method for spatial interpolation and evaluation of soil properties considered in this study. Spatial statistics indicated that WC, TP, PR, Ks, ECe, pH and clay content were spatially associated explaining some trends in soil variability within the field. The variations in soil properties in the A-horizon of CRP grassland may be affected by topographic position characteristics, erosion, vegetation history, weather conditions and previous farming practices.
Technical Abstract: Knowledge of the spatial variability of soil properties in agricultural fields is important for implementing various precision agricultural management practices. This paper examines spatial variation of selected soil physical and chemical properties and explores their spatial correlation in the A horizon of a Lihen sandy loam soil (sandy, mixed, frigid Entic Haplustoll) within a field of grass-alfalfa CRP land. Soil measurements were made on a 16 m * 36 m grid sampling pattern. Soil properties including penetration resistance (PR), bulk density ('b), and gravimetric water content ('m) were measured by collecting undisturbed soil cores from 5 - 10 cm and 20 - 25 cm depths. Additional disturbed soil samples were collected for particle size distribution, electrical conductivity (ECe) and pH analysis. The two depths were averaged for the assessment of spatial distribution, relationships and interpolation of soil properties. Soil saturated hydraulic conductivity (Ks) and total porosity ('T) for the 0 ' 25 cm depth were estimated from 'b, 'm, and volumetric water content at field capacity (FC) level. Soil properties were analyzed using both classical and geostatistical methods that included descriptive statistics, semivariograms, cross-semivariograms, spatial kriged and co-kriged prediction maps and interpolation. Results indicated that small to moderate spatial variability existed across the field for soil properties studied. Furthermore, cross-semivariograms exhibited a strong negative spatial interdependence between soil PR and 'm, 'T, and lnKs. Spatial variability of soil 'm, 'b, PR, ECe, pH and clay content and their spatial correlation in the A-horizon of the CRP grassland were attributed to a combination of previous farming practices, topographic characteristics, vegetation history, soil erosion, and weather conditions at this site.