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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Water Management and Conservation Research » Research » Research Project #431759

Research Project: Quantitative Assessments of Water and Salt Balance for Cropping Systems in Lower Colorado River Irrigation Districts

Location: Water Management and Conservation Research

Project Number: 2020-13660-008-003-I
Project Type: Interagency Reimbursable Agreement

Start Date: Sep 15, 2016
End Date: Mar 31, 2022

This project aims to improve Yuma agricultural productivity and sustainability by quantifying and tracking water use and salt balance across typical Yuma crop production systems and rotations over multiple years. Measurements of germination, growth and yield will be collected and related to the water use and salt balance values. Current estimates of annual water and salt balance in space and time are limited and uncertain. These balances will be greatly improved by collecting water and salt measurements in the field, analyzing samples in the lab, and modeling irrigation practices.

The core activities of this water and salt tracking project will be conducted in the field. These studies will be initiated prior to the summer fallow irrigation. The data loggers and sensors monitoring soil salt and soil moisture will remain in the field compiling data until land preparation operations begin for fall produce planting. The ionic composition of the water will be tracked throughout the system. This will be accomplished by sampling the source water, water collected in the catch cans, and soil saturated paste extracts. Major cations (Ca, Mg, Na, K) and anions (Cl, SO4) will be measured. Charge balance will be calculated to evaluate if additional ion quantification will be necessary. Cation ratios (Ca:Na:Mg:K) will also be calculated for all samples to validate that dissolved salt are conserved through the system. Anions will be quantified using membrane suppression ion chromatography. Cations will be quantified using flame atomic absorption spectrophotometry. To assist with the development of a strategy for evaluating the performance of an on-farm irrigation system, surface irrigation data will be analyzed to determine infiltration and hydraulic resistance characteristics. Simulations of the irrigation system will be conducted using an unsteady flow model taking into account water and salt flow processes, and the impact of irrigation practices on salt distribution in the soil profile will be characterized.