The occurrence of legacy P soils and potential mitigation practices using activated biochar

Long-term application of manures in watersheds with dense animal production has increased soil phosphorus (P) concentration, exceeding plant and soil assimilative capacities. The P accumulated in soils heavily manured and containing excess extractable soil P concentrations is known as legacy P. Runoff and leaching can transport legacy P to ground water and surface water bodies contrib-uting to water quality impairment and environment pollution, such as eutrophication. This review article analyzes and discusses current and innovative management practices for soil legacy P. Specifically, we address using biochar as an emerging novel technology to reduce P movement and bioavailability reductions in legacy P soils. We illustrate that properties of biochar can be affected by pyrolysis temperature and by various activating chemical compounds and byproducts. Our approach consists of engineering biochars using activation process on poultry litter feedstock before pyrolysis to enhance binding or precipitation of legacy P. Finally, this review article will describe previous examples of biochar activation and will offer new approaches to produce bio-chars with enhanced P sorption capabilities.

Impact/Purpose

Long-term application of manures in watersheds with dense animal production has increased soil phosphorus (P) concentration, exceeding plant, and soil assimilative capacities, often leading to P movement into down gradient water bodies that can result in eutrophication. This review article considers and evaluates current literature on best management practices to reduce or eliminate offsite movement of P. It specifically focuses on using biochar production from animal wastes/manures to sorb and retain excess P to reduce offsite P movement and to reduce P bioavailability. Through a review of the literature we illustrate that biochar properties that affect P sorption and retention are influenced by biochar feedstock selection, biochar production temperature and pre- and post-pyrolysis activation. We conclude that by using engineered biochar made from poultry litter as a soil amendment in soils with excess P that soil P can be captured and effectively managed to reduce offsite movement of P thereby reducing the likelihood of water quality impairment and environment pollution, such as eutrophication. Using this innovative technology will be a valuable tool for land and environmental managers in areas with known issues with excess soil P.

Citation

Cerven, V., J. Novak, A. Szögi, K. Pantuck, D. Watts, AND M. Johnson. The occurrence of legacy P soils and potential mitigation practices using activated biochar. American Society of Agronomy, MADISON, WI, 11(7):1289, (2021). [DOI: 10.3390/agronomy11071289]

DOI: The occurrence of legacy P soils and potential mitigation practices using activated biochar