Elucidating the impact of broiler litter and pinewood biochar on metal retention and leaching in undisturbed soil columns using simulated rainfall

Authors: BRAR, GURPARSHAD - Auburn University; MALHOTRA, KRITIKA - University Of Southern California; KUMAR, RAKESH - Auburn University; LAMBA, JASMEET - Auburn University; Way, Thomas; PRASAD, RISHI - Auburn University; ADHIKARI, SUSHIL - Auburn University

Submitted to: Journal of Hazardous Materials Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2025
Publication Date: 9/11/2025
Citation: Brar, G.S., Malhotra, K., Kumar, R., Lamba, J., Way, T.R., Prasad, R., Adhikari, S. 2025. Elucidating the impact of broiler litter and pinewood biochar on metal retention and leaching in undisturbed soil columns using simulated rainfall. Journal of Hazardous Materials Advances. 20:100860. https://doi.org/10.1016/j.hazadv.2025.100860.
DOI: https://doi.org/10.1016/j.hazadv.2025.100860

Interpretive Summary: Broiler litter is a mixture of manure from broiler chickens and a bedding material such as wood shavings. Broiler litter is a good source of nutrients for crops, and it also contains trace metals (e.g., aluminum) and heavy metals (e.g., zinc and copper). The objective of this study was to examine the effect of application method (surface broadcast vs. subsurface banding) of broiler litter and pine wood pristine biochar on the leaching of copper, zinc, aluminum, iron, nickel, and chromium via preferential flow in soil. Cylindrical soil cores, 15 cm diameter and 50 cm depth, were collected from the sandy loam soil of a pasture in northeastern Alabama. In the lab, we simulated rainfall by irrigating the soil surface of each core, and leachate water was collected after it flowed down through each soil core. The treatments we used on the soil cores in the lab were (1) surface-applied broiler litter, (2) subsurface-banded broiler litter, (3) surface-applied broiler litter + biochar, (4) subsurface-banded broiler litter + biochar, and (5) control (no biochar and no broiler litter). Extremely low amounts of nickel and chromium were collected in the leachate water. Treated cores leached more copper and zinc, while the amounts of aluminum and iron in leachate were similar in treated and control columns. Incorporation of pristine biochar along with broiler litter helped reduce metal leaching.

Technical Abstract: Repeated and long-term application of broiler litter to agricultural land can lead to metal leaching into subsurface soil and groundwater quality issues through preferential flow pathways. The objective of this study was to examine the effect of application method (surface broadcast vs. subsurface banding) of broiler litter and pine wood pristine biochar on the leaching of copper, zinc, aluminum, iron, nickel, and chromium via preferential flow in soil. Cylindrical soil cores, 15 cm diameter and 50 cm depth, were collected from the sandy loam soil of a pasture in northeastern Alabama, and used for a rainfall simulation experiment in the lab. Treatments were surface-applied broiler litter, subsurface-banded broiler litter, surface-applied broiler litter + biochar, subsurface-banded broiler litter + biochar, and control (no biochar and no broiler litter). For each treatment, three rainfall simulations were performed: simulation 1 (0th day), simulation 2 (5th day), and simulation 3 (10th day). Bromide breakthrough curves confirmed the presence of preferential flow down through the soil for all soil cores. Nickel and chromium were below the detection limits in leachate samples. Treated cores leached more copper and zinc as a result of soluble metals in broiler litter, and changes in soil pH and dissolved organic matter, enhancing metal mobility. However, the amounts of aluminum and iron in leachate were similar in treated and control columns, as most aluminum and iron were bound in immobile fractions in soil and litter. With successive simulations, leaching of copper, zinc, and aluminum decreased, while iron leaching from surface and subsurface applied broiler litter-treated columns increased over time, resulting from reducing conditions. Incorporation of pristine biochar along with broiler litter helped reduce metal leaching.