Research Project: Innovative Manure Treatment Technologies and Enhanced Soil Health for Agricultural Systems of the Southeastern Coastal Plain

Location: Coastal Plain Soil, Water and Plant Conservation Research

2025 Annual Report

Objectives
1. Develop and test improved tillage, cover crops, and biomass management to enhance soil health and resiliency and improve long-term agricultural sustainability and productivity in the Southeastern Coastal Plain. 2. Develop manure treatment and handling systems that minimize the emissions of greenhouse gases, antimicrobial resistance genes, odors, nutrients, and pathogens to improve soil health and water quality outcomes. 2.A. Develop new, affordable treatment technologies for removal/recovery of manure nutrients from swine, poultry, and dairy operations and industrial/municipal wastes. 2.B. Conduct multiscale assessment of the impact of manure treatment and nutrient management systems on agricultural ecosystem services for soil conservation and water quality protection. 2.C. Increase the value of agricultural residuals using hydro- and thermal technologies. 2.D. Develop improved techniques for quantifying ammonia deposition near livestock production sites. 3. Develop biostimulants and other soil amendments and assess their ability to improve soil health, nutrient cycling, and soil fertility and resiliency. 3.A. Develop and assess microbial inoculants and other soil amendments for their ability to enhance revegetation and improve drought resistance in remediated and degraded soils. 3.B. Develop biochar and hydrochar applications to improve their use in agricultural and non-agricultural settings.

Approach
New management practices and treatment technologies are required to help crop and animal producers increase soil productivity and health; reduce unwanted atmospheric emissions, excessive nutrients, and pathogens; and improve affordability of animal waste treatment. To meet these needs, we aim to develop in this project: i) knowledge of the impact of crop systems and novel soil amendments on the soil ecosystem and nutrient and carbon cycling; ii) new manure treatment technologies; iii) model-based approaches to evaluate nutrient and gas emission reduction strategies; iv) management strategies to reclaim degraded soils; v) management practices to reduce pathogens and antimicrobial resistance genes in agricultural wastes; and vi) knowledge of and metrics for properties that make a soil more productive. The project has three objectives. Improved tillage, cover crops, and biomass management will be developed to enhance soil health and resiliency and improve long-term agricultural sustainability and productivity in the Southeastern Coastal Plain. Innovative manure treatment systems will be developed to minimize greenhouse gas emissions, and reduce antimicrobial resistance genes and pathogens, odors, and excess nutrients, to improve soil health and water quality outcomes. The manure treatment technologies include recovery of ammonia using gas-permeable membranes, enhanced deammonification treatment, and engineered biochar and hydrochar systems to valorize agricultural residuals. Manure management's beneficial impact will be assessed using multiscale models, and improved techniques will be used to assess ammonia emissions from manure, including deposition near livestock operations. Biostimulants and other soil amendments will be investigated for their ability to improve soil health, nutrient cycling, soil fertility, and resiliency. Research methods include laboratory, pilot-scale, and field-scale experiments using modern analytical equipment. Research products will advance the state-of-the-science for more effective conservation and management of soil resources, innovative animal waste treatment technologies as environmentally safe alternatives to traditional land application, and guidelines for beneficial byproduct utilization.

Progress Report
Cotton and soybean biomass samples were collected in fall of 2024. Yield data for both crops have been summarized, and the samples are currently being analyzed for elemental composition to determine nutrient update and use efficiency. Cover crops were planted immediately after harvesting cotton and soybean in fall 2024. Cover crop biomass samples were collected in spring 2025 and are also being analyzed for nutrient content. (1a) The LiCOR LI-8100A Automated Soil CO2 Flux System is currently deployed at the site and taking hourly CO2 flux readings. This is the second consecutive year since modifications were made on the system deployment method. CO2 data will be retrieved and summarized periodically throughout the growing season to ensure proper functioning of the system. All CO2 data will be analyzed at the end of this cropping season. (1b) Soil samples were collected immediately following cotton and soybean harvest in Fall of 2024. All soil samples have been processed and awaiting analysis for soil chemical properties including pH and electrical conductivity, soil carbon and nitrogen pools, as well as other essential nutrients including soil P. (1c) Data on soil health indicators have been analyzed, and manuscript on the impacts of tillage, cover crops, and crop rotation on soil health is currently under preparation. (1d) Along with CRADA partner, Pancopia, tested an on-farm nitrification system for anaerobically digested swine wastewater, with recycling into barns in a closed loop, to measure the impacts to animal health. Results indicate significant improved animal health outcomes using this treatment system. (2a1) A novel electrochemistry methodology was developed for the simultaneous recovery of N and P that eliminates the need for alkali solutions required for N capture via gas-permeable membranes, and acidic solutions required for subsequent P solubilization. Over 85% of N, and 94% of P was recovered from liquid swine manure using this novel system, and a patent has been filed on the system. (2a2) Testing of P and protein extraction using lactose waste in dairy manure was completed. (2a3) Sludges have been collected from several municipal wastewater treatment plants and swine wastewater lagoons. Samples were characterized prior to further experimentation, and an initial round of P extractions were performed. (2a4) A learning-based algorithm was trained and tested for retrieving the geolocations and areas of swine waste treatment lagoons from high-resolution aerial RGB and NIR ortho-imageries. Results showed meaningful algorithm performance for lagoon-based swine farm detection (accuracy>98%, precision>81%) and lagoons area estimates (r2>0.88). The new algorithm is employed to generate watershed-wide lagoon-based swine CAFOs dataset which will be used in a SWAT modeling framework to quantify the water reuse potential from swine CAFOs given different scenarios of waste treatment systems. (2b) Greenhouse experiments were conducted at Louisiana State University to determine the effect of plastichar derived from cotton gin trash and waste plastic on tomato yields and the reduction of harmful gases. Conducted batch sorption experiments to evaluate cadmium sorption by plastichar derived from manure and plastic waste as a function of pH, ionic strength, biochar dosage, and time. (2c1) Hydrothermal carbonization was performed and products were evaluated for biogas potential. Data analysis has been analyzed and a manuscript is currently under preparation. (2c2) ARS researchers at Florence, North Carolina conducted trace gas release experiments with methane and ammonia gases known concentrations. The data are used to calibrate important parameters of the STAGE computer model for estimating ammonia deposition flux. (2d) Samples were collected from LEM restoration sites and analyzed. Manuscript was written on soil health analysis of experimental plots using compost as an organic amendment. (3a1) Microbial inoculant was applied for a fourth year, soil measurements were collected and analyzed. An additional study across the Cotton Belt was conducted, involved ARS researchers in Florence, SC performing microbial viability and community identification. Results demonstrated microbial inoculants were ineffective in boosting cotton yields, and were unable to significantly influence positive impacts to cotton plants or soil. A manuscript on this study is currently in preparation. (3a2) Performed laboratory incubation experiments evaluating the effect of nonactivated and iron-activated biochar on plant-available P from two high-P soils (Queponco and Pepperbox Series). For each soil, statistical correlations between plant-available P and biochar application rate, feedstock, and activation were analyzed. (3b1) Mine spoil from the Formosa Mine Superfund Site (Riddle, OR) was acquired and the material characterized. Laboratory incubation experiments were performed to determine the effect of biochar application on rainfall-leachable aluminum, copper, and zinc. (3b2)

Accomplishments
1. New system for recovering nitrogen and phosphorus from livestock wastewater using electrochemistry. Conservation and recovery of nitrogen (N) and phosphorus (P) from livestock, industrial, and municipal effluents are important because of economic and environmental reasons. Therefore, a need exists for improved systems and methods for N and P recovery from wastewater, especially in using fewer chemicals. ARS scientists at Florence, South Carolina developed a new method using electrochemistry to enhance the rate of ammonia capture by a gas-permeable membrane and the rate of phosphate capture using P-precipitating compounds. The process was tested using swine manure effluent that contained great amounts of N and P. The process recovered most of the ammonia and the phosphorus contained in the manure. The wastewater’s ammonia was removed from the anode chamber and recovered in the stripping acid solution with 86% recovery efficiency. For example, using P-precipitating compounds calcium and magnesium, the process recovered 93% to 95% of the total P in a P precipitate solid compared to only 4.6% to 6% in a control without electrochemical treatment. All these were accomplished without adding hydroxide or acid chemicals. The new system is expected to offer livestock producers a better way to manage the ammonia and phosphorus in their facilities, and to add a new income stream to the farm through the sale of concentrated fertilizers produced on-site from waste materials.

2. Learning-based algorithm for recognizing and estimating physical proprieties of Swine Waste treatment using Aerial Ortho-Imagery. The Southeast US swine industry constitutes a major economic activity contributing to the national food security. However, the use of open-air lagoons for long-term storage of swine waste raises environmental concerns, but transforming the waste into worth is shown as a pathway to sustain investment in advanced waste treatment technologies. Yet, precise data on individual swine lagoon geolocation and area are needed to accurately scale up the potential benefits of alternative waste treatment technologies on nutrient recovery, wastewater reuse, or harmful gas emission curtailment. ARS researchers in Florence, South Carolina in collaboration with researchers at the University of Texas Arlington, developed a learning-based algorithm for detecting and retrieving the physical features of swine waste treatment lagoons from high-resolution aerial ortho-imageries. The algorithm was structured to mimic the human capacity to recognize swine lagoons in the agricultural landscape as farms’ design is very distinctive including concentrated feeding barns with open-air lagoons. Results showed that the trained algorithm was able to detect and geolocate lagoon-based swine farms with an accuracy above 98% and a precision above 81% while it also showed a high performance at estimating individual lagoon areas (r2>0.88). This algorithm can be used to generate detailed information on lagoon-based swine farms across the Southeast US. The new algorithm is an inexpensive alternative for in-situ surveying of swine farms and a pathway to accommodate the biosecurity constraints of farms. The algorithm outputs can be useful for the remote assessment of the potential implications of alternative waste treatment systems on individual farms and help extension specialists make recommendations to farmers based on the specificities of their farms in the agricultural landscape.

Review Publications
Sohoulande Djebou, D.C., Vanotti, M.B., Szogi, A.A. 2025. Evaluating IPCC methodologies for estimating methane emission from lagoon-based swine manure management systems. Environmental Quality. 34(4). Article e70079. https://doi.org/10.1002/tqem.70079.
Sohoulande Djebou, D.C., Ma, L., Qi, Z., Szogi, A., Stone, K.C., Harmel, R.D., Martin, J.H., Birru, G.A., Sima, M. 2024. Agronomic and environmental effects of forage-cutting schedule and nitrogen fertilization for bermudagrass (Cynodon Dactylon, L.). Agriculture, Ecosystems and Environment. 378. Article 109318. https://doi.org/10.1016/j.agee.2024.109318.
Sohoulande Djebou, D.C. 2025. Spatial analysis to retrieve SWAT model reservoir parameters for water quality and quantity assessment. Water. 17(6):834. https://doi.org/10.3390/w17060834.
Umeobi, E.C., Ducey, T.F., Johnson, M.G., Ippolito, J.A. 2025. Soil health alterations via compost additions to natural and remediated heavy metal-contaminated mineland soils. Environmental Science and Pollution Research. 32:14968-14979. https://doi.org/10.1007/s11356-025-36602-1.
Tian, W., Tang, Y., Ducey, T.F., Khan, E., Tsang, D. 2024. Novel roles of biochar for dark fermentation in strengthening links between hydrogen evolution and energy conservation by facilitating flavins-based transmembrane and extracellular electron transfer. Journal of Environmental Science and Technology. 58(40):17766-17776. https://doi.org/10.1021/acs.est.4c05994.
Paye, W.S., Herrero, R.M., Vanotti, M.B., Szogi, A.A., Read, Q.D. 2025. Agronomic effectiveness of nitrogen and phosphorus recovered from swine manure. Agrosystems, Geosciences & Environment. 8.Article e70153. https://doi.org/10.1002/agg2.70153.
Smith, S., Gaston, L., Beasley, J., Wang, J., Padilla, J.T., Wenguang, S. 2024. Ironstone and red mud barriers to reduce lateral movement of soil phosphorus. Journal of Environmental Quality. 53(5):758-766. https://doi.org/10.1002/jeq2.20601.
Calvo-De Diego, P., Garcia-Gonzalez, M., Riano, B., Vanotti, M.B., Sanchez-Bascones, M., Molinuevo-Salces, B. 2025. A biorefinery approach to recover nutrients, proteins, and methane from raw swine manure. Journal of Environmental Management. 389. https://doi.org/10.1016/j.jenvman.2025.126254.