An online soil moisture based irrigation scheduling tool (SMIST)

There is one common problem associated with water balance calculation methods for determining soil moisture for scheduling irrigation, i.e., the errors in the estimated soil moisture are cumulative and a regular recalibration is needed. Pan (2012) developed a simple and robust approach to estimate daily soil moisture using a daily diagnostic soil moisture equation. The estimated soil moisture is a function of the time-weighted summation of the ratio of historical precipitation rate to the soil moisture loss coefficient. To capture the seasonal variation of soil moisture loss coefficient, a sinusoidal wave function of the Day of Year (DOY) is used to represent the seasonal variation of the loss coefficient. A three-year continuous dataset of daily soil moisture and daily precipitation collected at each of four Soil Climate Analysis Network (SCAN) sites, i.e., AR2091 in Arkansas, GA2013 in Georgia, NM2107 in New Mexico, and PR2052 in Puerto Rico, is applied to test the proposed method. The land cover and land use of these four sites are agricultural/crop fields, grasslands, or desert. The root mean square errors of the estimated volumetric soil moisture are less than 5%(V/V) and the correlation coefficients R2 are all greater than 0.78. The results indicate that there are three advantages associated with the suggested approach: 1) non-cumulative errors in the estimated soil moisture, and thus 2) no regular recalibration requirement, and 3) no numerical iteration and initial moisture information needed. The long-term goal of this project is to increase agricultural irrigation efficiency in arid and semi-arid regions by providing farmers with an easy-to-use, robust soil moisture driven irrigation-scheduling tool (SMIST).



• Pan F. and Nieswiadomy M., Estimating daily root-zone soil moisture in snow-dominated regions using an empirical soil moisture diagnostic equation. Journal of Hydrology, 542, 938-952, 2016. (Link)


• Pan F., Nieswiadomy M., and Qian S., Application of a soil moisture diagnostic equation for estimating root-zone soil moisture in arid and semi-arid regions. Journal of Hydrology, 524, 296-310, 2015. (Link)


• Pan F., Estimating daily surface soil moisture using a daily diagnostic soil moisture equation. Journal of Irrigation and Drainage Engineering, 138(7), 625-631, 2012. (Link)


• Pan F., Peters-Lidard C.D., and Sale M.J., An analytical method for predicting surface soil moisture from rainfall observations. Water Resources Research, 39(11), Art. No. 1314, 2003. (Link)