Location: Agricultural Water Efficiency and Salinity Research Unit
Project Number: 2036-61000-018-000-D
Project Type: In-House Appropriated
Start Date: Feb 6, 2017
End Date: Feb 5, 2022
Objective 1: Evaluate the effects of degraded irrigation waters on crop water use and yield at commercial production scales. Subobjective 1A: Evaluate the impact of salinity on crop water use and productivity by observing evapotranspiration and carbon fluxes in commercial almond and pistachio orchards exhibiting a range of salinities. Subobjective 1B: Develop quantitative relationships between remotely-sensed plant canopy observations and measured crop water use and productivity. Objective 2: Develop an innovative, open informatics platform for disseminating information, tools, and recommendations for the management of marginal quality irrigation and artificial recharge waters. Subobjective 2A: Develop a web-based platform for disseminating information, tools, and recommendations for evaluating and managing saline irrigation waters. Subobjective 2B: Develop improved models to support managed aquifer recharge (MAR) treatment of alternative water resources for irrigation. Objective 3: Develop a set of sensing technologies that measure soil and solution properties relevant to the use of low quality waters for irrigation, including salinity, sodicity, clay content, aluminum, iron oxides, organic matter, and soil solution boron concentration. Sensor technologies will include near-infrared (NIR), mid-infrared (MIR), and x-ray fluorescence (XRF) spectroscopy. Objective 4: Develop and evaluate an integrated system of tools for site-specific irrigation management to control soil salinity and related adverse conditions when using degraded waters. The integrated multiple-sensor system will combine the use of geospatial apparent soil electrical conductivity (ECa), y-ray spectrometry, and multi-spectral imagery. Subobjective 4A: Develop and evaluate an integrated multiple-sensor system (1) to delineate matric and osmotic stress patterns at field scale and (2) to enhance the robustness of regional-scale salinity assessment modeling. Subobjective 4B: Develop a set of integrated tools to diagnose and manage infiltration problems due to sodic conditions by modeling the chemical effects on infiltration reduction and quantifying soil sodicity.
Drought, climate change, and competition for resources are reducing the availability of irrigation water and farmland in arid and semi-arid regions. One strategy for maintaining or enhancing productivity in the face of diminished resource availability is to make greater use of marginal lands and alternative water sources, both for irrigation and for recharging depleted aquifers. Sustainable use of low-quality waters requires soil, water, and crop management practices that optimize crop production and aquifer recharge while minimizing the degradation of natural resources by salts and other contaminants. Advanced multi-sensor technologies, models, and decision-support tools are needed to evaluate alternative management practices and to assist growers and water managers in satisfying increasingly stringent regulations. In this project, we propose a combination of field studies and laboratory experiments designed to develop knowledge and technologies needed to enable optimal use of fresh, degraded, and recycled waters for irrigation and recharge. In the laboratory, we undertake a series of experiments to test the hypothesis that portable near-infrared (NIR), mid-infrared (MIR), and x-ray fluorescence (XRF) sensors can be calibrated to measure soil chemical properties, and ultimately can be used in the field to observe changes in soil properties and guide management. The influences of soil texture, mineralogy, EC, pH, ESP, water content, and surface roughness on sensor calibration and performance will be assessed. A second group of experiments will evaluate the effects of irrigation water quality (SAR, pH, EC) on the long-term impact of irrigation and rainfall on the infiltration capacity of soils of varying textures. Two major field campaigns are planned. In the first, we field-test a multi-sensor platform for delineating field-scale spatial variations in soil salinity and texture and identifying associated matric and osmotic stress patterns. The platform consists of gamma ray (y-ray) and electromagnetic induction (EMI) instrumentation in combination with Landsat 7 multi-spectral imagery. In the second campaign, we use micro-meteorological methods to evaluate field-scale crop productivity and water-use across a network of research sites in commercial orchards exhibiting a range of soil salinities and irrigation water qualities. Finally, we develop modeling tools focusing on two problems associated with alternative waters and managed aquifer recharge operations: (i.) decreasing infiltration due to soil clogging by colloids; and (ii.) infiltration depths and setback distances required to ensure microbial safety at groundwater extraction points. And lastly we develop an open, web-based informatics platform for disseminating information, models, and decision-support for the use of saline irrigation waters. The project should lead to improved recommendations for managing alternative water resources for irrigation and recharge, and produce new capabilities for predicting the effects of management decisions on crop yields and on soil and water quality.