Project Number: 2036-61000-017-00-D
Project Type: In-House Appropriated
Start Date: Dec 8, 2016
End Date: Mar 3, 2018
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).