REMEDIATION TECHNIQUES FOR MANURE NUTRIENT LOADED SOILS Hailin Zhang 1 , Thanh H. Dao 2 , Nicholas T. Basta 1 , Elizabeth A. Dayton 1 , Tommy C. Daniel 3 SUMMARY Many soils in the United States contain excessive levels of nutrients, especially phosphorus (P), due to repeated heavy applications of animal manure. Also, soils with a history of long-term poultry litter or swine manure applications have elevated levels of copper (Cu), zinc (Zn), selenium (Se), and arsenic (As). Runoff and eroded soils carry dissolved and sediment-associated nutrients to wa- ter bodies and degrade their quality. Manure-treated fields can also impair air quality by emitting odorous compounds and dust. Several best management practices (BMPs) have the potential to re- duce nutrients in runoff water and loading to surface waters. The BMPs were grouped into two broad categories: (1) technologies to reduce excessive nutrient levels in the soil, and (2) technolo- gies to reduce edge of field discharges of nutrients via runoff or sediment loss from over- application of manure or other organic biosolids. Potential remedial approaches for nutrient-loaded soils include: • Phytoremediation (P, nitrate, metals) with plant species that preferentially bioaccumulate nu- trients or metals and use of deep-rooted crops in novel rotations for subsurface nitrate-N re- covery; • Soil and manure amendments with P immobilization chemicals and municipal or industrial by- products to reduce dissolved reactive P and metal bioavailability (water treatment residuals, aglime, coal combustion by-products); • Addition of soil aggregation promoters, coagulants or flocculants such as polyacrylamide polymers to reduce sediment and particulate nutrient offsite discharges (organic matter, N, P, metals); • Deep mechanical tillage to dilute near-surface zone elevated nutrient concentrations and re- duce odor emissions (P, metals, odor, trace greenhouse gases); and • Conservation buffer strips to remove dissolved reactive P from runoff and reduce edge-of-field losses of sediments and particulate nutrients and metals. Growing high biomass-yielding plants can remove large amounts of nutrients and may be a promising remedial strategy to export and reduce excess soil nutrients. Bermudagrass and certain warm-season annual grasses produce large dry matter yields, and thus take up large quantities of applied nutrients. Cool-season grasses and certain legumes have a higher uptake of certain nutri- ents, such as P, and may remove more specific nutrients than bermudagrass, although their yield potential is not as high. Various plant species, including Brassica, preferentially concentrate Cu, Se, and As from high metal soils. Using forage to extract P and specific metals in problem soils has been an effective approach, but is slow to lower soil levels. Grazed-only systems will not effec- tively remove nutrients from an over-application site since most of the applied nutrients, especially P and K, are redeposited on the land during grazing. Research using soil amendments has shown that land application of drinking water treatment re- siduals potentially reduces dissolved P in runoff water by up to 70% from land with excessive lev- els of soil test phosphorus. Other materials such as fly ash and flue-gas desulfurization products from coal combustion in electric power generation and aglime are readily available and also effec- 1 Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK. 2 USDA-ARS, Henry A. Wallace Beltsville Agricultural Research Center, Animal Manure and By-Products Laboratory, Beltsville, MD. 3 Department of Agronomy, University of Arkansas, Fayetteville, AR. Pp. 482-504 in Animal Agriculture and the Environment: National Center for Manure and Animal Waste Management White Papers. J. M. Rice, D. F. Caldwell, F. J. Humenik, eds. 2006. St. Joseph, Michigan: ASABE. Pub. Number 913C0306.