Location: Agricultural Water Efficiency and Salinity Research Unit
Project Number: 2036-61000-019-018-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Aug 1, 2024
End Date: Jul 31, 2026
Objective:
California and the other Colorado River Basin Compound members face stark challenges due to water scarcity with increasing pressure on agricultural water users. Efficient irrigation is mandatory to manage scarce water resources. To address this challenge, accurate estimates of crop water evapotranspiration (ETc) support growers in optimizing on-field water use and efficiency in sugarbeet and other key crops grown in Imperial Valley. Sugarbeets are primarily a winter crop, which reduces the potential water demand compared with a summer crop. Sugarbeets can also scavenge nitrogen from the soil and grow in higher soil salinity than other crops. This study proposes using the eddy covariance method, as ground truth, for estimating and comparing ETc data with open-source satellite models. We also aim to evaluate consumptive water use, efficiency, and crop productivity under multiple irrigation systems. The ultimate goal is inform the decision-making process of the California of Beet Growers Association with up to date information about the efficiency of differing irrigation methods.
Approach:
The proposed project will be conducted at the Imperial Valley in two cropping cycles. This methodology describes the first cropping cycle. This project aims to evaluate water use and efficiency and compare sugarbeet evapotranspiration under common irrigation systems. Crop water use and OpenET comparison will be performed using remote sensing, specifically eddy covariance methodology (Dhungel et al., 2023; French et al., 2020). A full eddy covariance tower measures carbon dioxide exchange between the plant canopy and the atmosphere, enabling assessing crop stress and productivity, unlike energy balance or surface renewal systems (Montazar et al., 2020). We will partition fluxes using Flux Variance Partitioning (Skaggs et al., 2018) to determine how photosynthesis and soil evaporation differ between the irrigation methods and to identify if there is a potential for irrigation savings. To assess crop water use, three full eddy covariance towers in sugarbeet fields with contrasting furrow and sprinkler irrigation systems (Anderson et al., 2017) will be installed in Fall 2023 and operated for two cropping cycles. Care will be taken to select three fields planted at similar times with similar soil types.
Eddy covariance observations in sugarbeets will also be used to better train the Agricultural Input Management with Artificial Intelligence (AIM-AI) algorithm sugarbeet. Extending AIM-AI sugarbeets will be funded as part of the base US Salinity Laboratory project for 2022-2027. Eddy covariance observations will provide highly valuable validation and calibration data.
Part of the funded technician time will be dedicated to running an intercomparison of the suite of OpenET models against measured eddy covariance ET. Season long OpenET accuracy and shorter scale deviations would be assessed. The goal is to evaluate whether OpenET models can effectively monitor sugarbeet ET in the Imperial Valley and if OpenET accuracy varies depending on the irrigation system.
We propose to conduct pre- and post- season surveys of all three fields with EM-38 (Scudiero et al., 2017) and gamma ray sampling (Scudiero et al, 2023 – under review). ESAP software will be used to direct soil sampling at each field to translate apparent electrical conducitivity into extract electrical conductivity useful for agronomic and irrigation management. Soil textures will be analyzed for samples and related to gamma ray surveys to map variations in textures across the field. Analysis of pre- and post-season electrical conductivity will be used to evaluate the impact of irrigation method on salinity control and to assess potential water savings though a reduction in leaching fraction.
