Nutrient Chemistry of Manure and Manure-Impacted Soils as Influenced by Application of Bauxite Residue

Abstract

Adequate management of animal manure and manure-affected soils is important for sustainable animal production as nutrient runoff from agricultural fields with long-term application of animal manure has caused great concerns over its impacts on the environment. This chapter demonstrates the effects of using bauxite residue, a by-product from the aluminum refinery industry, to modify nutrient characteristics of animal manure and manure-affected soils. The chapter begins with an introduction of bauxite residue properties followed with different aspects of treatment effects including pH, phosphorus (P) chemistry, mobility of nitrogen (N), organic carbon (OC), trace metals with focus on zinc (Zn), copper (Cu) and arsenic (As) as well as fecal coliforms in animal manure and manure-affected soils. Bauxite residue generally improves the nutrient characteristics of animal manure by suppressing the leaching potential of water-soluble P, NH4-N, OC, Zn, Cu and As. It also decreases populations of fecal coliform in manure. The high organic nature of animal manures appears to be able to buffer the alkalinity contributed from the bauxite residues, preventing a substantial increase in pH of the treated manures and manure-affected soils although the soil sodium adsorption ratio (SAR) is elevated. Sorption and transport of phosphate in soil amended with bauxite residue indicate that bauxite residue can be used as possible reactive permeable barriers. Seawater neutralized bauxite residues, in general, exhibit greater retention of P and trace metals than un-neutralized ones. Bauxite residue addition up to 10 % (w/w) had no effect on the growth of transplanted switchgrass seedlings. Overall, bauxite residues could be used as a potential amendment for reducing P and other contaminant leaching in animal manures and manure-affected soils, and manure-bauxite residue treatment improves the application of both wastes for beneficial use.