6 - Impact of sewage sludge application on microbial diversity and fertility of soil: A long-term study

Abstract

Sewage sludge application in agricultural soil is a remedial option for substituting expensive chemical fertilizers which plays an important function in improving the physiochemical and biological properties of soil in various ways. However, benefits of sludge on the biological properties of soil are based on organic carbon and metal concentration which directly affects the beneficial flora and fauna of the soil and plants. The physical characteristics of soil are improved by the application of sewage sludge. It includes soil porosity, water-holding potential, stability of soil, and formation of aggregate and bulk density of soil. However, an excessive use of SSA (sewage sludge application) in agricultural fields for longer period will increase bioavailability of heavy metals like arsenic, chromium, lead, nickel, and zinc. It causes bioaccumulation of such toxic metals in edible portions of field crops above the economic threshold level or safe limits and ultimately causes biomagnification in both plants and humans. Soil containing elevated amounts of metals decreases the microbial population, diversity, and activities. This chapter focuses on the long-term impact of sewage sludge, heavy metal accumulation on fertility of soil, and influencing soil microbial diversity. It will also cover bioavailability to plants and different methods for removing metals from the contaminated soil for its possible use in agriculture.