Location: Soil and Water Management Research
Title: COSMOS soil water sensor compared with EM sensor network & weighing lysimeter Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 3, 2014
Publication Date: January 4, 2014
Citation: Evett, S.R., Schwartz, R.C. 2014. COSMOS soil water sensor compared with EM sensor network & weighing lysimeter.[abstract] W2188 Multi-State Soil Physics Committee Meeting, January 2-4, 2014, Las Vegas, Nevada. Technical Abstract: Soil water sensing methods are widely used to characterize the root zone and below, but only a few are capable of delivering water content data with accuracy for the entire soil profile such that evapotranspiration (ET) can be determined by soil water balance and irrigations can be scheduled with minimal error. Scientist with the USDA-ARS Conservation & Production Research Laboratory, Bushland, Texas, evaluated: a) the neutron probe (NP), which when field calibrated and appropriately used can resolve ET over weekly or longer intervals with acceptable accuracy for most uses; b) the Cosmic Ray Soil Moisture Observing System (COSMOS), which responds to surface soil water content changes in a circular area of radius up to several hundred yards; and c) electromagnetic (EM) soil water sensing methods. These were intercompared and compared as well with a large precision weighing lysimeter that measured soil water storage changes to within 0.04 mm (<0.01 inch). COSMOS was well correlated with 0-30 cm water content and storage as measured by the field-calibrated EM sensors. COSMOS responded to rainfall better than to subsurface drip irrigation at 30-cm depth. COSMOS was biased upward by green, living vegetation. The COSMOS "effective depth" algorithm did not work well in this case; but assuming that the effective depth was constant at 30 cm depth resulted in good correlation with EM measured soil water storage. The wireless EM sensors system worked very well, providing timely information that correlated well with weighing lysimeter soil water storage data. The wireless EM sensor system would be very useful for irrigation scheduling since the tall corn crop did not result in signal and data loss, and the data accurately represented soil water content as it changed over time due to irrigation and precipitation.