Degree Type


Date of Award


Degree Name

Master of Science


Agricultural and Biosystems Engineering

First Advisor

Amy L. Kaleita


Soil moisture is an important component of numerous systems, influencing crop development, and runoff and infiltration partitioning, among other things. However, due to its spatial and temporal variability, it is difficult to estimate soil moisture consistently using conventional techniques such as gravimetric sampling, which is point-based and time-consuming. Therefore, to overcome this drawback in soil moisture estimation and mapping, and to facilitate its measurement spatially and temporarily, remote sensing in microwave, visible, near infrared and short wave infrared is being explored and is proving to be a promising technique. But to develop models using spectral data there is a need to validate these models using ground truth data collected using gravimetric measurements and various dielectric and capacitance probes. Theta probe is one such dielectric probe, which is widely used by the remote sensing community. Not only does soil surface conditions change the response of reflectance data in various spectral ranges but has been observed to influence the measurements from Theta probe. As a part of this study an attempt has been made to understand the influence of soil temperature, roughness and crusting on Theta probe measurements by analyzing moisture content as a function of time. A nonlinear relationship was observed between the actual moisture content and Theta probe soil moisture content. A t-test conducted on the estimate of temperature concluded that the effect of temperature on Theta probe measurements was insignificant, but there is a possibility that soil surface conditions involving soil roughness and crusting could be a reason for observed nonlinearity between actual and Theta probe measurements. Therefore, future work is suggested to test the feasibility of using Theta probe under different soil surface conditions.



Digital Repository @ Iowa State University,

Copyright Owner

Geetika Dilawari



Proquest ID


File Format


File Size

49 pages