IRT-Based Irrigation Scheduling and Dry Bean Crop Water Productivity Under Different Irrigation Scenarios in the Nebraska High Plains

Authors

• Angie Gradiz, University of Nebraska-LincolnFollow

First Advisor

Xin Qiao

Second Advisor

Wei-zhen Liang

Date of this Version

5-2024

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Mechanized Systems Management

Under the supervision of Professors Xin Qiao and Wei-zhen Liang

Lincoln, Nebraska, May 2024

Comments

Copyright 2024, Angie Gradiz. Used by permission

Abstract

Irrigation plays a critical role for crop production in western Nebraska of the United States, where crop evapotranspiration often exceeds in-season precipitation. This study investigated the impacts of different irrigation treatments on yield and key physiological parameters of dry edible beans grown in semi-arid western Nebraska during the 2022-2023 growing seasons. Seven irrigation levels (0%, 25%, 50%, 75%, 100%, 125%, 150%) of the fully irrigated treatment (FIT), were applied using a Variable Rate Irrigation (VRI) Linear-Move Sprinkler System. Additionally, an eighth treatment was scheduled based on measurement from infrared radiometry thermometers (IRT) to evaluate the performance of the two-source energy balance (TSEB) model. The ET derived from TSEB (ET_TSEB) was compared to actual evapotranspiration (ET_a) and crop evapotranspiration (ET_c) calculated from FAO-56 single crop coefficient approach. Furthermore, irrigation water use efficiency (IWUE) and normalized water productivity (WP_b) were compared between treatments and across different production years. Results showed that applying 75% of the FIT did not significantly decrease yield across the three seasons. The 75% FIT also exhibited the highest IWUE with an average of 0.87 kg m^-3 and represented a 28% increase compared to IWUE of 100% FIT. Conversely, the 125% treatment showed the lowest IWUE at 0.43 kg m^-3. The ET_TSEB performed better on estimating ET compared to ET_a (RMSE: 2.1 mm day^-1) than to ET_c (RMSE: 2.5 mm day^-1). Pooled regression across the production seasons yielded a dry bean WP_b of 14 ± 0.47 g m^-2 with an R² of 0.76. A significant contrast in slope between the vegetative and reproductive stages was observed for dry beans. Specifically, during the vegetative stage, the slope was measured at 12.1 g m^-2 with an R² of 0.55. In contrast, during the reproductive stage, the slope decreased to 8.98 g m^-2 with an R² of 0.38.

Advisors: Xin Qiao and Wei-zhen Liang