Location: Agricultural Water Efficiency and Salinity Research Unit
2024 Annual Report
Objectives
Drought, climate change, and competition for resources are reducing the availability of irrigation water and farmland in arid and semi-arid regions, including the western United States. 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. Sustainable use of impaired waters requires soil, water, and crop management practices that optimize crop production while minimizing the degradation of natural resources by salts and other contaminants. Advanced models and decision-support tools are needed to evaluate alternative management practices and to assist growers and water managers in satisfying increasingly stringent regulations.
Objective 1: Develop and deploy digital technologies, models, and best management practices for the management of saline and sodic soils and the safe use of alternative water resources for irrigation.
Sub-objective 1.A: Develop and evaluate an integrated system of sensors for site-specific irrigation management to control soil salinity and related adverse conditions when using degraded waters.
Sub-objective 1.B: Develop databases and machine learning models for rapid estimation of soil-hydraulic and related parameters needed in water quality models and decision support tools.
Sub-objective 1.C: Investigate wastewater reuse and water quality impacts on soil properties and contaminant loading to underlying and downstream water resources.
Sub-objective 1.D: Expand user-friendly, web-based informatics and modeling platform for the diagnosis and management of saline and sodic soils.
Objective 2: Develop comprehensive datasets for agricultural water use, crop productivity, and carbon balance in salt-affected, semi-arid regions for a range of crops using various management practices.
Sub-objective 2.A: Observe water use and crop productivity in contrasting mature citrus varietals to determine potential time periods for applying deficit irrigation for water conservation.
Sub-objective 2.B: Extend artificial intelligence tools for water, nutrient, and salinity management to perennial specialty crops in Southern California.
Objective 3: Determine the G x E x M interactions related to crop salt tolerance and drought resistance.
Sub-objective 3.A: Evaluate the impact of regenerative agricultural practices in wine grapes on productivity, water use, and resilience to abiotic stress.
Approach
This project uses a combination of field, plot, and modeling studies to develop knowledge and technologies needed to enable optimal use of fresh, degraded, and recycled waters for irrigation.
Under Objective 1, it is hypothesized that for saline soils a multi-sensor platform consisting of gamma-ray spectrometry and electromagnetic induction (EMI) instrumentation combined with Landsat 7 spectral imagery will improve the spatial delineation of salinity and matric and osmotic stress patterns at field scale. To test the hypothesis, the spatial distribution of salinity and texture using EMI alone, EMI and gamma-ray spectrometry in combination, and EMI and gamma-ray in combination with spectral imagery will be compared to ground-truth measurements. Three field sites in the southwestern U.S. containing a range of soil textures, salinities, and parent materials will be evaluated.
The robustness of the U.S. Salinity Laboratory (USSL) regional-scale salinity assessment model will be enhanced by: (i.) incorporating orchards and vineyards into the model; (ii.) modifying and validating ECa-directed soil sampling protocols for fields under drip irrigation; (iii.) evaluating the reliability and credibility of the USSL regional-scale model through validation with a separate data set; and (iv.) establishing the temporal stability of the USSL regional-scale salinity model.
Databases and machine learning models for rapid estimation of soil-hydraulic and related parameters will be developed. Soil hydraulic properties will be measured in the laboratory using evaporation and dew point methods. A new standardized database of training data for developing and testing pedotransfer functions will be produced. A web-based platform will be developed for disseminating information, tools, and recommendations for evaluating and managing saline irrigation waters.
Plot scale studies will be conducted at the USSL in Riverside, California. A vegetable crop will be grown in rows irrigated periodically with either synthetic or collected tertiary treated wastewater by surface drip lines. Waters will contain a baseline concentration of inorganic and prominent antibiotic contaminants adjusted to a range of salinity levels. A cross section of contaminant distribution and speciation across the wetting zone in relation to soil chemistry and mineralogy will be determined.
Under Objective 2, water use and crop productivity in contrasting mature citrus varietals will be monitored to determine possible time periods for applying deficit irrigation for water conservation. Uncertainties and variances between different monitoring techniques (eddy covariance, surface renewal, and simplified surface renewal) will be evaluated.
Under Objective 3, the Agricultural Input Management tool with Artificial Intelligence (AIM-AI) will be extended. AIM-AI is an artificial intelligence tool for water, nutrient, and salinity management currently being developed for Imperial, Coachella, San Jacinto, Salinas, and San Joaquin Valleys. The current project expands the reach of AIM-AI to specialty perennial crops in Central and Southern California, including citrus, dates, wine grapes, and avocados.
Progress Report
This report documents fiscal year (FY) 2024 progress for project 2036-61000-019-000D, titled, “Water Management for Crop Production in Arid and Semi-Arid Regions and the Safe Use of Alternative Water Resources”, which started in February 2022.
In support of Sub-objective 1.A, apparent electrical conductivity (ECa)-directed soil sampling protocols specifically developed for drip-irrigated tree crops were used to survey and sample 39 orchards to provide a database to improve the robustness of the regional-scale San Joaquin Valley salinity model developed from the fusion of proximal and satellite sensor data. Four additional fields were surveyed in 2024 totaling 39 fields over the past three years. The 39 fields were surveyed and sampled in collaboration with University of California Cooperative Extension personnel.
Progress on laboratory characterization of soil hydraulic properties under Sub-objective 1.B was also limited due to the abolishment of a technical support position. A great many soil sample analyses (e.g., particle size distribution, bulk density, saturation percentage, salinity) have been completed, but full hydraulic property measurements have been limited. ARS researchers in Riverside, California, are exploring possible collaborations with university partners as they seek to continue work on this aspect of the sub-objective. Also, in support of Sub-objective 1.B, relationships among soil moisture at various depths were analyzed using data from 4,712 agricultural sites in the contiguous United States. A relatively strong association between 10 and 20 cm soil moisture was found, while the association was weaker at deeper depths. Climate, vegetation, and soil type all affected the observed relationships, particularly at deeper depths. The findings are being evaluated for their implications for extrapolating satellite-based surface soil moisture data to deeper depths. In support of Sub-objective 1.D, progress continued on the development of new software for assessing various soil, water, and plant processes, as well as providing information on the characterization and management of salt-affected soils.
For Sub-objective 1.C, ARS researchers in Riverside, California, continue to investigate the impact of treated municipal wastewater (TMW) on the nutritional and antioxidant capacity of fresh vegetables irrigated with alternative water source. This experiment is part of a larger project that investigates the potential dissemination of antibiotic-resistant bacterial genes through the soil-plant-earthworm continuum into food-production systems. One current experiment evaluated the nutritional and antioxidant value of spinach and radish plants irrigated with TMW in soil amended with 2% cow manure. TMW did not affect the nutritional value or antioxidant capacity of either crop. However, manure increased the concentrations of potassium and phosphorus in both crops. Manure significantly reduced the concentration of sodium absorbed by both crops. Also, the combination of TMW and manure significantly increased spinach shoot yield, and both shoot and tuber yield in radish, although not significantly. Results support the use of TMW as an alternative to freshwater.
In additional support of Sub-objective 1.C, ARS researchers in Riverside, California, have worked with a doctoral student from Brazil and a visiting scholar from Uzbekistan to evaluate the effect of saline waters ranging from half the salt composition of seawater to full seawater salinity on the growth and yield halophyte (salt-loving) quinoa genotypes. In the first experiment, quinoa plants of two genotypes were irrigated with saline waters of 2.0, 25, 40, and 55 deci-siemens per meter (dS/m). One of the genotypes grew better and produced more grains than the other under the same salinities but plants, in general, lost up to 60% of their yield under seawater salinity. In the second experiment, quinoa plants were irrigated with freshwater for different periods before switching the irrigation to saline water of half of salt-strength seawater (25 dS/m). Plants were irrigated with freshwater for 100% of their life cycle, 75%, 50%, 25%, and 0% (100% saline water). Plants grew better and produced more grains when the irrigation with saline water was delayed to the final 50% and 75% of their life cycle. However, quinoa plants still survived and produced grains when irrigated with 25 dS/m water 100% of their cycle. Deliverables: a manuscript is in preparation with the scholar from Uzbekistan and two manuscripts are currently in preparation with the results from the Brazilian doctoral student. The student has concluded her doctoral requirements from her Brazilian university and has received her doctoral degree in soil sciences.
Under Objective 1, a field study was set up and conducted at the United States Salinity Laboratory to probe the mitigation of antimicrobial resistance determinant (ARD) dissemination in drip irrigated spinach and radish systems with biochar amendments. The study was conducted to probe mitigation under both manure and wastewater-borne ARD inputs and with two distinct biochar amendments. While the study has not been fully analyzed yet, the results will serve to elucidate the impact of biochar in reducing plant uptake and microbial transformation by ARDs in the soil environment. Moreover, this study will help understand how biochar serves as a nutrient source and soil amendment in drip irrigated systems in comparison with other soil amendments (e.g., manure).
Objective 1 was further addressed through production of a range of 24 biochars (four different types of feedstocks and six pyrolysis temperatures) and assessment for removal of antibiotics, antibiotic resistance genes and bacteria from solution. Results from these studies indicate excellent removal of all antibiotics studied, although with different biochars showing variable removal based on pyrolysis temperature and feedstock. Relationship between removal behavior and production condition-dependent biochar characteristics will be better established through these studies and are being used to inform the developments of larger-scale column filtration systems. Bench-scale filtration systems have been designed, constructed, and tested for their removal of antibiotics from treated wastewaters. These studies have shown that appropriate selection of biochar adsorbents can lead to highly effective removal of antibiotic compounds when treated wastewaters are pumped through the biochar materials. Larger (greenhouse) scale systems are currently being constructed and tested for their removal efficacy towards per- and poly-fluoroalkyl substances (PFAS). These systems will also be applied to antibiotics. Ultimately, such systems will lead to low-cost, environmentally friendly treatment options for producing treated wastewaters with low contaminant loadings for use in agricultural irrigation, thereby helping prevent risks to the human food chain.
Supporting Objective 2, ARS researchers in Riverside, California, continued operation of two eddy covariance towers in citrus orchards in collaboration with a researcher from Parlier, California. A third eddy covariance tower was installed in a novel trellised citrus orchard with different canopy architecture and irrigation strategy. A Research Associate at Riverside, California, continued work on evaluating satellite evapotranspiration estimates for these orchards, which resulted in a peer-reviewed article being submitted in FY24. Work in citrus has highlighted significant limitations in using the OpenET evapotranspiration algorithm and project for managing citrus irrigation. In support of Sub-objective 2.B, work by a Research Associate in Riverside, California, on an externally funded project (2036-61000-019-006-R), was evaluated for potential transferability to domains covered by this project plan. Ongoing work by a Research Associate in Riverside, California, on an externally funded project (2036-61000-019-006-R), contributed significantly to Objective 2 of this project through enhanced satellite remote sensing of crop water use in specialty crops and detection of early season irrigation using daily, commercial, multi-spectral imagery, which resulted in a peer-reviewed publication in FY24.
For Objective 3, ARS researchers in Riverside, California, continued a collaborative research effort on the impacts of regenerative agricultural practices on wine grape resilience to abiotic stresses. Farmer-directed treatment plans were continued in an experimental vineyard, ongoing soil and microbial samples were collected, and three monitoring stations (meteorology and soil moisture) were maintained in the vineyards. More experiments are being set up to assess biological soil activity (for example, soil respiration and specific enzyme activities) in conventional and regenerative plots for the first-year sampling. Additionally, preliminary results were generated looking at the time-resolved soil chemical changes, such as soil carbon and nitrogen contents, nutrient speciation and salinity, that may have occurred in the converted regenerative vineyard soils after one year of regenerative management. Soil sampling will be continued to follow soil properties in managed vineyard soils through time.
Accomplishments
1. New algorithm enables identification of early season irrigation events using daily satellite imagery. Knowing when early-season irrigation events occur is critical for accurately running crop water use models and determining likely total irrigation amounts for regional water management. However, accurately assessing when irrigation events occur is laborious and infeasible at regional scales. ARS researchers in Riverside, California, have leveraged the recent advent of daily, high-resolution commercial satellite imagery to identify irrigation events by capturing the spectral change in soil reflectance following wetting after an irrigation event. When tested against field records of irrigation, the approach accurately identifies irrigations when canopy cover is less than 30%. This tool will help improve regional scale modeling of crop water use and be useful for data providers who seek to automate irrigation calculations for farmers.
2. Improved understanding of dissemination of antimicrobial resistance in agricultural ecosystem. The increasing demand for food production and the expansion of irrigated agriculture have put significant pressure on water resources, particularly in arid and semi-arid regions. Identifying and developing effective methods for tracking the dissemination of antimicrobial resistance in the agricultural production environment is a recent goal of many International and National Organizations. ARS researchers in Riverside, California, working in collaboration with University of California at Riverside researchers, used high throughput quantitative polymerase chain reaction (PCR) to quantify the number of genes, mobile genetic elements, and antibiotic-resistant bacteria present in spinach and radish. Researchers found that the number of antibiotic resistance genes were significantly higher in spinach compared to radish, and there was a strong correlation between genes and microbial diversities in the spinach and radish production environment. Thus, changes in the abundance of antibiotic resistance genes may exert selective pressure on the microbial community, influencing its composition and diversity. This study provides new knowledge to assist farmers, researchers, and wastewater management professionals in reducing the dissemination of antimicrobial resistance in agricultural systems, ultimately protecting the public from the threat of antimicrobials.
3. Use of biochar to mitigate the impacts of per- and polyfluoroalkyl substances (PFAS) in agriculture. Growing concern over the presence of per- and polyfluoroalkyl substances (PFAS) in agricultural compartments (e.g., soil, water, plants, soil fauna) has led to an increased interest in scalable and economically feasible remediation technologies. In this comprehensive review paper, ARS researchers in Riverside, California, framed biochar as a strategy for mitigating the detrimental impacts of PFAS in agricultural systems and discuss the benefits of this strategy within the framework of the needs and challenges of contaminant remediation in agriculture. To gauge the optimal physicochemical characteristics of biochar in terms of PFAS adsorption, principal component analysis using more than 100 data points from the available literature was performed. The main biochar-based PFAS treatment strategies (water filtration, soil application, mixing with biosolids) were also reviewed to highlight the benefits and complications of each. Life cycle analyses on the use of biochar for contaminant removal were summarized, and data from selected studies were used to calculate (for the first time) the global warming potential and net energy demand of various agriculturally important biochar classes (crop wastes, wood wastes, manures) in relation to their PFAS adsorption performance. The concepts introduced in this review may assist in developing large-scale biochar-based PFAS remediation strategies to help protect the agricultural food production environment.
Review Publications
Shveytser, V., Stoy, P.C., Butterworth, B., Wiesner, S., Skaggs, T.H., Murphy, B., Wutzler, T., El-Madany, T.S., Desai, A.R. 2024. Evaporation and transpiration from multiple proximal forests and wetlands. Water Resources Research. 60(1). Article e2022WR033757. https://doi.org/10.1029/2022WR033757.
Firmano, R.F., Peak, J.D., Schmidt, M.P., Alleoni, L.R. 2023. Phosphate and myo-Inositol hexakisphosphate adsorption onto hematite as affected by Ca2+, Mg2+, and pH. ACS Earth and Space Chemistry. 7(12):2420-2429. https://doi.org/10.1021/acsearthspacechem.3c00192.
Bhattacharjee, A.S., Phan, D., Zheng, C., Ashworth, D.J., Schmidt, M.P., Men, Y., Ferreira, J.F., Muir, G., Hasan, N.A., Ibekwe, A.M. 2023. Dissemination of antibiotic resistance through soil-plant-earthworm continuum in the food production environment. Environment International. 183. Article 108374. https://doi.org/10.1016/j.envint.2023.108374.
Bhattacharjee, A.S., Phan, D., Zheng, C., Ashworth, D.J., Schmidt, M.P., Men, Y., Ferreira, J.F., Muir, G., Hasan, N., Ibekwe, A.M. 2024. Dissemination of antibiotic resistance genes through soil-plant-earthworm continuum in the food production environment. Environmental International. 183. Article 108374. https://doi.org/10.1016/j.envint.2023.108374.
Dhungel, R., Anderson, R.G., French, A.N., Skaggs, T.H., Saber, M., Sanchez, C., Scudiero, E. 2023. Early season irrigation detection and evapotranspiration modeling of winter vegetables based on Planet satellite using water and energy balance algorithm in lower Colorado basin. Irrigation Science. 42(1):15-27. https://doi.org/10.1007/s00271-023-00874-7.
Zhang, Y., Xu, Y., Skaggs, T.H., Ferreira, J.F., Chen, X., Sandhu, D. 2023. An advanced protocol for profiling RNA-binding proteins in Arabidopsis using plant phase extraction. Biology Methods and Protocols. 8(1). Article bpad016. https://doi.org/10.1093/biomethods/bpad016.
Keremane, M.L., Singh, K., Ramadugu, C., Krueger, R., Skaggs, T.H. 2024. Next generation sequencing, and development of a pipeline as a tool for the detection and discovery of citrus pathogens to facilitate safer germplasm exchange. Plants. 13(3). Article 411. https://doi.org/10.3390/plants13030411.
Lazarovitch, N., Kisekka, I., Oker, T.E., Brunetti, G., Wöhling, T., Xianyue, L., Yong, L., Skaggs, T.H., Furman, A., Sasidharan, S., Raij-Hoffman, I., Šimunek, J. 2023. Modeling of irrigation and related processes with HYDRUS. Advances in Agronomy. 181:79-181. https://doi.org/10.1016/bs.agron.2023.05.002.
Scudiero, E., Corwin, D.L., Markley, P.T., Pourreza, A., Rounsaville, T., Bughici, T., Skaggs, T.H. 2024. A system for concurrent on-the-go soil apparent electrical conductivity and gamma-ray sensing in micro-irrigated orchards. Soil and Tillage Research. 235. Article 105899. https://doi.org/10.1016/j.still.2023.105899.
Schmidt, M.P., Ashworth, D.J., Ibekwe, A.M. 2024. Cephalexin interaction with biosolids-derived dissolved organic matter: Binding mechanism and implications for adsorption by biochar and clay. Environmental Science: Water Research & Technology. 10:949-959. https://doi.org/10.1039/D3EW00590A.
Ashworth, D.J., Schmidt, M.P., Ibekwe, A.M. 2023. Performance of acid- and base-modified biochars for the removal of antibiotics from water under dynamic conditions. Journal of Environmental Chemical Engineering. 11(6). Article 111616. https://doi.org/10.1016/j.jece.2023.111616.