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Research Project: Management of Degraded Waters for Irrigation: Integrated Field-scale Systems using Multi-sensor Technology


2019 Annual Report

The overarching goal of this project is to integrate multi-sensor technology, knowledge of chemical and physical processes, and computer modeling of water, solute, and trace element transport into a water management system for optimal use of fresh, degraded, and recycled waters for irrigation with the following objectives. Objective 1: 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 2: 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 2a: 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 2b: 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.

Objective 1 Hypothesis: Portable near-infrared (NIR), mid-infrared (MIR) and x-ray fluorescence ( XRF) sensors can be calibrated in the lab to measure soil chemical properties, and used to observe changes in soil properties for management. Sensors will be tested under different soil conditions. Three portable sensors will be used: NIR, MIR, and XRF. Four experiments have been conceived. The 1st experiment evaluates in the lab the influence of texture, mineralogy, EC, pH, ESP, water content, and surface roughness on sensor measurements. Statistical relationships between properties and sensor will be quantified. The 2nd experiment looks at the sensors’ spectra and evaluates each sensor’s ability to identify soil properties of interest. The 3rd experiment evaluates the findings of experiments 1 and 2. The 4th experiment develops site-specific sensor calibrations for fields in Subobjective 2a. Objective 2a Hypothesis: A multi-sensor platform of y-ray and electromagnetic induction (EMI) combined with Landsat 7 multi-spectral imagery will improve the spatial delineation of salinity and texture to better identify field-scale matric and osmotic stress patterns. Spatial distribution of salinity and texture using EMI alone, EMI and y-ray in combination, and EMI and y-ray in combination with spectral imagery will be compared to ground-truth measurements. Sensor platform will be tested on 3 fields varying in texture, water content, salinity, sodicity, trace elements and parent material. An initial exploratory statistical analysis determines correlation coefficients between sensors and soil properties followed by a more extensive statistical analysis using spatial regression models. The goal is to enhance the robustness and credibility of the regional-scale salinity model developed at the US Salinity Lab by: (a) incorporation of orchards and vineyards into the model, (b) evaluation of a hybrid model that combines the annual integral approach with the multi-year approach, (c) validation of the model with an independent data set, and (d) establishment of the model’s temporal stability by comparing model prediction and measured data for the 1st & 5th years. Objective 2b Hypothesis: Long-term effects of irrigation and rainfall on the infiltration of water in soils at various SAR, pH, and EC will demonstrate a greater Na hazard than traditionally based short-term laboratory leaching studies. Experimental Design: Evaluate changes in infiltration over an 8-month period both under combined simulated rain and irrigation alone for a sandy loam soil, with irrigation treatments of 3 levels of pH and 5 levels of SAR (0, 2, 4, 6, 8, and 10). Soils will be prepared and irrigated or rain applied at a soil water potential of -50MPa. The calculated infiltration rates will be related to soil texture, and soil chemical conditions (EC, SAR, and pH).

Progress Report
During FY19, this project merged with project 2036-61000-018-00D. This is the final report for this project. In future years, see the 2036-61000-018-00D annual report for updates on these objectives. Considerable progress has been made in support of Objective 1, quantifying the effect of various soils parameters (e.g., salinity, sodium, pH, and boron) on mid infrared (MIR) and portable x-ray fluorescence (PXRF) measurements. Thirteen soils of varying texture and mineralogy previously analyzed for various soil chemical properties in the laboratory were used in the evaluation of hand-held sensors to be used in the field to predict chemical and physical information relevant to the mapping and management of saline soils. PXRF is used for the measurement of chemical elements. Using soils of known soil properties, the effect of water content and different soil textures, sodium adsorption ratio (SAR), and salinity on elemental composition without external calibration was evaluated for PXRF. The PXRF sensor was affected by water content, with increased water content attenuating the signal for all elements. The instrument was stable at low water contents, thus suitable for field application of surface soils. Chloride (Cl-) content could be semi-quantitatively determined to Cl- concentrations of 20 milli-equivalents per liter (Cl- concentration expressed in the standard format of saturation extract). Measurements of water content and clay content with handheld Fourier transform infrared spectroscopy (FTIR) using the MIR region were initiated. MIR spectra were collected for a set of 13 soil samples of varying clay content (7 to 43%). MIR spectra of soils in the lab were collected under various conditions in the range of 400 cm-1 to 4000 cm-1 for samples with particle size up to 2 cm diameter. The 1200 to 1700 cm-1 range was utilized for determination of clay content. A R2 of 0.81 was obtained for prediction of clay content based on peak area, indicating that the method is a viable tool for obtaining field clay content measurements. This technology will complement field electromagnetic conductivity measurements for field mapping and management of salinity. The information is of use to researchers working on remote sensing of salinity and is expected to improve field-scale diagnosis of salinity problems thus assisting growers and extension specialists. A critical physical science technician position vacancy that has existed for the past 30 months has had a major impact on the progress of field work crucial to Sub-objective 2A. Collaboration with the University of California, Davis, Cooperative Extension and the seasonal hiring of limited appointments have partially helped to offset the lack of qualified technical support. Under Sub-objective 2A, an integrated multiple-sensor system consisting of apparent soil electrical conductivity (ECa), gamma-ray spectrometry, and multi-spectral imagery sensors is needed to measure and manage the complex spatial patterns of water content and salinity created when using degraded irrigation waters and to improve the robustness of the U.S. Salinity Lab regional-scale salinity model, which is currently unable to predict salinity on drip-irrigated orchards and vineyards. Subsequently, an integrated system of ECa, gamma-ray spectrometry, and real-time kinematic global position system sensors has been designed on a single mobile platform. The platform was tested in a drip-irrigated citrus orchard with mixed results. Following rainfall events where the soil profile throughout the field was uniformly moist, ECa and gamma-ray spectrometry measurements were reliable in delineating texture, soil moisture, and soil salinity. However, when spatial measurements of ECa and gamma-ray spectrometry were taken under micro-irrigation systems, ECa measurements were no longer reliable. The fusion of ECa and gamma-ray data no longer provided reliable maps, suggesting that refinements in the protocols in directed soil sampling from the fusion of ECa and gamma-ray data were needed. Because of the complex 3-dimensional nature of soil moisture and soil salinity distributions under drip irrigation, previous ECa-directed soil protocols are no longer sufficient. A modified set of protocols to characterize the abrupt local-scale variations in soil moisture and salinity that occur under drip irrigation is needed. Further testing of the multiple-sensor platform on drip-irrigated fields is needed in the future using newly developed protocols. Additionally, under Sub-objective 2A, ground truth soil salinity data obtained from ECa field surveys with mobile electromagnetic induction (EMI) and soil sampling equipment is needed to improve the current U.S. Salinity Lab regional-scale model for mapping salinity in the root zone for the San Joaquin Valley (SJV) and to validate the model. From 2017 to 2019 twenty-one fields were identified in the SJV providing a wide range of soil salinities within drip-irrigated orchards. The 21 fields were surveyed for salinity following ECa-directed soil sampling protocols developed at the U.S. Salinity Lab over the past three decades. The intention was to use the 21 fields to improve the robustness of the U.S. Salinity Lab regional-scale model for mapping salinity in the SJV. Results from Sub-objective 2A and the ECa surveys of the 21 drip-irrigated orchards in the SJV indicated the need for modified ECa-directed soil sampling protocols that better address the abrupt changes in soil moisture and salinity that accompany micro-irrigation systems. Current ECa-directed soil sampling protocols fail to develop a robust ECa-salinity calibration for micro-irrigation systems due to inherent soil sampling design inadequacies. Since improving the robustness of the regional-scale salinity model for the SJV (Sub-objective 2A(2)) depends on the incorporation of orchards and vineyards, which are almost completely under drip irrigation, the development of revised ECa-directed soil sampling protocols specific to micro-irrigation is essential to Sub-objective 2A. An experimental design was developed to establish revisions of ECa-directed soil sampling protocols and guidelines specific to fields under micro-irrigation. The experimental design was conducted and completed on two fields. Two drip-irrigated pistachio fields on Flores Orchard Farm in the SJV were selected based on their range of soil salinity. Both ranged in salinity from moderate to high. Within each field, soil cores were taken at six within-field locations. At each of the six locations, six cores were taken to a depth of 1.5 meters (m) at 0.3-m increments. All soil samples were dried, ground, sieved, and analyzed for salinity (i.e., ECe), water content, and saturation percentage. The results indicated that the protocols to calibrate ECa to salinity (EC of the saturation extract, ECe) for a drip-irrigated field required a minimum of two soil cores at each within-field location with one taken at the drip line and the other taken 0.9-1.2 m perpendicular to the drip line. To validate the revised protocols a drip-irrigated pistachio field in the SJV near Coalinga, California, was used. An ECa survey was conducted to identify 12 locations within the field that reflected the range and spatial variation of the ECa measurements. Two soil cores were taken, one in the drip line and the other 1.2 m perpendicular to the drip line. Each core was taken to a depth of 1.5 m at 0.3-m increments. All soil samples were dried, ground, sieved, and analyzed for salinity (i.e., ECe), water content, and saturation percentage. Statistical analysis and linear regression modeling were used to calibrate ECa to salinity. Calibration models developed from the cores taken in the drip line and from combined cores from the drip line and 1.2 m from the drip line were statistically compared. A second drip-irrigated field was selected for further validation on a soil substantially different from the Coalinga field. The second field is a date palm grove in California’s Imperial Valley. The field has been surveyed for ECa, soil samples have been taken as described for the Coalinga field, and all soil samples are in the process of analysis for salinity (i.e., ECe), water content, and saturation percentage. Statistical analysis and linear regression modeling remain to be performed. Results indicated that all 21 SJV fields that were previously assessed for salinity from 2017-2018 to improve the U.S. Salinity Lab regional model will need to be resampled following modified ECa-directed soil sampling protocols specific to fields under micro-irrigation. This information is valuable to inventory soil salinity levels across the SJV, to monitor the impact of changes in climate patterns on salinity development, and to provide water resource managers and decision makers with information to assist in irrigation water allocations for salinity control. Under Sub-objective 2B, significant progress was made. Sustaining irrigated agriculture in arid and semi-arid regions will require the use of less fresh water and corresponding increases in alternative water supplies of lower quality. A manuscript was prepared and submitted for publication discussing the results of the experiment to evaluate the effect of rain on infiltration when irrigating with waters of varying of SAR (sodium adsorption ratio) and pH. As there were no statistically significant interactions among the variable effects, the rain, SAR and pH effects on infiltration were separately quantified. Results indicated that short-term experiments under-estimate the adverse effects of elevated SAR and pH and that there is no threshold in SAR, any increase in SAR reduces water infiltration. This information is of significant interest to growers in regions where there is measurable rainfall, suggesting that in order to maintain infiltration, amendments are recommended to be applied whenever SAR of the irrigation water is above three.


Review Publications
Marino, G., Zaccaria, D., Snyder, R., Lagos, O., Lampinen, B., Ferguson, L., Grattan, S., Little, C., Shapiro, K., Maskey, M.L., Corwin, D.L., Scudiero, E., Sanden, B. 2019. Actual evapotranspiration and tree performance of mature micro-irrigated pistachio orchards grown on saline-sodic soils in the San Joaquin Valley of California. Agriculture. 9(4):75.