Date of Graduation

12-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Biological and Agricultural Engineering

Advisor

Benjamin R. Runkle

Committee Member

Michele L. Reba

Second Committee Member

Brian E. Haggard

Third Committee Member

Kusum J. Naithani

Keywords

alternate wetting and drying, ecohydrology, eddy covariance, evapotranspiration, rice

Abstract

Rice provides much needed sustenance to a large portion of the global population, particularly in the developing world. With stress placed on food production systems under the reality of climate change and an increasing global population, rice production systems require solutions to a number of issues, including a limited water supply. As producers explore new strategies for conserving local water resources to continue to maintain yields, new irrigation strategies and technologies are being developed and validated for use at commercial production scales. Alternate wetting and drying (AWD) is an irrigation practice that provides water savings through the capture of rainfall during periodic drying events during the growing season. The AWD practice also has relevance as a climate change mitigation measure as the periodic drying disrupts and reduces methane production commonly associated with continuously flooded rice. With drying introduced during the growing season, there is potential for AWD to cause drought stress that is harmful to the plant and may reduce yields. To validate AWD as a safe practice, the following work is focused on estimating and characterizing canopy water use as evapotranspiration (ET). In each chapter, ET is presented as a means to understand how drying may affect canopy water use. Furthermore, ET also has operational value in that accurate estimates of ET can be used to better inform irrigation management decisions for producers. To that end, we also explore ET estimation methods of varying complexity that can be used to assess the impacts of drying while also providing accurate estimates of ET throughout the growing season. Ultimately, our work provided validation for AWD as a safe irrigation practice that can be applied at the commercial scale.

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