Submitted to: Soil Science Society of America Journal
Publication Type: Book / Chapter
Publication Acceptance Date: June 17, 2000
Publication Date: N/A
Interpretive Summary: Prudent irrigation scheduling saves water and reduces the potential for non-point source pollution. Irrigation scheduling is typically based on soil/plant monitoring or evapotranspiration estimation, both of which have drawbacks. We developed a new model for estimating and forecasting the soil water and salinity status of soil underlain by shallow, saline groundwater. .The model was evaluated using data collected in an irrigated cotton field throughout the 1997 growing season. The model produced reasonable estimates of the average soil water content during the growing season, but the salinity estimates were less satisfactory. This work will be useful to researchers and others working on improved methods of irrigation scheduling that are based on forecasts of soil water and salinity conditions.
Technical Abstract: State space models based on mass balance principles and empirical flux laws can be used to estimate and forecast soil water and salinity regimes in the field. In this research, a state space model was developed that describes soil water and salinity dynamics and includes the effects of shallow, saline groundwater. The model was evaluated using daily time domain reflectometry (TDR) measurements of the soil water content and bulk soil electrical conductivity. Data were collected throughout the 1997 growing season in a field where cotton was being grown using an experimental shallow groundwater management technique. The model was tested by supposing that either weekly or biweekly profile-averaged measurements of water content and ECb were available, and then comparing the resulting filtered model forecasts with the full data set. The results show that the measured water content was within the predicted confidence intervals of one- or two- -week forecasts of the root zone average water content, soil water EC , and soil salinity. The predictions of the resident salt concentration (mass of salt per volume of soil) were less satisfactory.