Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2010
Publication Date: 2/15/2011
Citation: Stone, L.R., Klocke, N.L., Schlegel, A.J., Lamm, F.R. 2011. Equations for drainage component of the field water balance. Applied Engineering in Agriculture. 27(3):345-350. Interpretive Summary:
Technical Abstract: Accurate estimates of the drainage component of the field water balance are needed to achieve improved management of drainage in irrigated crop production systems and obtain improved estimates of evapotranspiration (ET) from soil water measurements. Estimating drainage for numerous soil and field conditions necessitates the use of simple, yet accurate, drainage equations containing easily measured parameters. The Wilcox drainage model is a relatively simple mathematical equation with a high degree of accuracy and applicability to field conditions. Our objectives were to develop Wilcox-type drainage rate equations for three coarse-textured soils of the west-central Great Plains and assemble previously determined, but fragmented, Wilcox-type drainage equations and supporting information for three medium-textured soils of the region. Drainage plots for collection of data for development of Wilcox-type drainage equations were established on two coarse-textured soil profiles in 2008 near Garden City, Kansas. Total water content of the soil profiles was measured over time during approximately 48-day drainage events. Total water was plotted against drainage time on log-log scales, and the linear regression equation relating the two variables was determined. These linear equations of profile water (log10) vs. drainage time (log10) were used to develop Wilcox-type drainage equations in which drainage rate (dW/dT in mm/day) is expressed as a function of soil profile water content (in mm). Drainage rate equations in this article can be used to estimate the drainage component of the field water balance for improved irrigation water management and more accurate estimates of ET from soil water measurements.