Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/14/2006
Publication Date: 11/14/2006
Citation: Jiang, P., Anderson, S.H., Kitchen, N.R., Sudduth, K.A., Sadler, E.J. 2006. Estimates of plant-available water capacity for claypan landscapes using soil electrical conductivity. ASA-CSSA-SSSA Annual Meeting Abstracts.
Technical Abstract: Landscape variability of plant available water (PAW) capacity is useful information for site-specific management, but is expensive to assess using traditional measurements. In this study, we hypothesized that for claypan soils, profile PAW capacity can be approximated by assuming a two-layer soil body, i.e., a silt loam topsoil layer, and a silty clay sublayer. Thus, PAW capacity can be mapped making use of previously-established relationships between surveyed soil electrical conductivity (EC) and topsoil thickness. The objective was to test this hypothesis against field-measured PAW capacity. Two claypan soil fields near Centralia, MO were sampled with 19 points in Field 1 and 18 points in Field 2 in March 2006 to determine field capacity. Lower limits of available water were determined at -1500 kPa pressure. Topsoil thickness was calculated using the best relationship (i.e., least biased with smallest prediction error against measured topsoil thickness) selected from several previously-developed calibration equations. Calculations were on a 1.2-m profile basis. PAW prediction errors between measured and estimated topsoil thickness were 12 cm for Field 1, and 17 cm for Field 2. Regression R2 values of estimated PAW against measured PAW were about 0.40 for Field 1 and 0.84 for Field 2. Prediction errors were 5.5 cm and 7.2 cm for Field 1 and Field 2, respectively. These prediction errors were 24% of the mean measured PAW for Field 1 and 34% for Field 2. Besides errors from topsoil thickness, errors in PAW estimation were also contributed by deviations from the assumed soil textures. Of particular note was the inclusion of layers beneath the claypan horizon that are typically silty clay loam which has a higher PAW capacity value than the assumed silty clay. Results of this study will provide insights on distribution of PAW and crop-water relations for crop-growth modeling and site-specific decision making.