Chapter 6 - Fly ash application in reclamation of degraded land: opportunities and challenges

Abstract

Fly ash (FA)—a coal combustion residue of thermal power stations—has been recognized as a soil ameliorator throughout the world. Usually, FA contains essential plant micro- and macronutrients and unique physicochemical properties. Besides, several hazardous substances, such as metal(loid)s, organic pollutants, and radioactive elements, are present in FA. FA disposal on land leads to unwanted changes in soil systems, including contamination with hazardous pollutants. Practical value of FA application in land offers extensive chances in soil systems, mainly for nutrient supplementation, pH correction, and ameliorating the soil physical conditions. In general, nitrogen and organic carbon are absent in FA. Moreover, phosphorus is also present in unavailable form. Therefore the coapplication of FA and organic waste is better suited than FA alone. Extensive studies showed that the lower doses of FA application in soil system modify the soil physicochemical, biological, and nutritional quality, while the higher doses of FA application results in metal(loid) toxicity and inhibits the microbial activity. The FA doses for each type of soil can be established after repeated field trials to confirm particular soil quality and safety. Organic waste amendment (i.e., press mud, farmyard manure, sewage sludge, agricultural waste, etc.) with FA should be applied as a low-input tool for reducing the FA toxicity. The present chapter discusses that how the unique FA physicochemical properties can be purposefully employed to ameliorate the acidic soil, sodic soil, mine spoil, as well as physical and fertility problems of the degraded soils. The chapter also argues how selection and application of the FA can be implemented to avoid phytotoxicity and minimize risk to the quality of crop productivity and environment. Overall, numerous studies have revealed that lower doses of FA could be successfully used in the degraded soil amelioration.