Biochar: Effects on Crop Productivity and Soil Properties

World food security is under challenge to a great extent due to effects of climate change, continued population growth and resource-depleting practices on agriculture (IAASTD, 2009). Presently poor farmers use either organic manure or inorganic fertilizers (Mando et al., 2005; Topoliantz et al., 2005) for maintaining soil fertility as they cannot afford to apply fertilizers as a nutrient source (Craswell and Lefroy, 2001). But the advantages of organic manure amendments are generally short-lived because of the rapid decomposition of soil organic matter under high temperature and aeration (Glaser et al., 2002). Therefore, organic amendments are applied every year to sustain soil productivity. An alternative to this practice could be the use of more stable compounds such as biochar (Glaser et al., 2002) instead of the easily degradable organic manures. The pyrolysis conversion of waste biomass into biochar is attracting international attention. Biochar is a solid carbon-rich organic material generated by heating biomass at 300–600oC under condition of limited or no oxygen (Lehmann and Joseph 2009). In the past few years, there has been growing interest in the use of synthetic biochar as an amendment worldwide for the following two reasons. Firstly, biochar can be used as a soil amendment for improving soil quality and secondly, storing biochar in soils is regarded as a means for permanently sequestering carbon (Hossain et al 2010) and enhancing agricultural productivity. Agronomic effects of biochar on crop yield and soil physico-chemical properties have been reported in many studies (Tryon, 1948; Kishimoto and Sugiura, 1985; Glaser et al., 2002; Lehmann et al., 2003; Chan et al., 2007; Rondon et al., 2007; Chan et al., 2008; Asai et al., 2009). The carbon-rich “Amazonian dark soils” (Arthrosols) are evidence, which host distinct microbial communities in comparison with adjacent carbon-poor soil, and have higher microbial biomass and diversity as well (O Neill et al 2009). The properties of biochars such as pH, nutrients, C-content, porosity, and surface area can significantly affect the biochemical and biophysical mechanisms of interaction between soil microfauna, mesofauna, and macrofauna in turn affecting soil ecosystem responses (Ameloot et al. 2013; Lehmann et al. 2011). Systematic evaluation of the use and function of various biochars in agricultural soils in terms of changes to physical-chemical and biological soil properties which are typically dictated by the type of amended biochar is a rapidly developing area of research (Jeffery et al. 2011; Barrow 2012; Meyer et al. 2011; Sohi et al. 2010; Biederman and Harpole 2013; Lehmann et al. 2011; Filiberto and Gaunt 2013). On the basis of recommendations from recent review studies (Jeffery et al. 2011; Verheijen et al.2014; Barrow 2012; Gurwick et al. 2013; Liu et al. 2013; Sohi et al. 2010; Atkinson et al. 2010; Huang et al. 2013; Biederman and Harpole 2013; Ameloot et al. 2013), it is becoming evident that the effects of biochar feedstock and production processes on the physical-chemical and biological indicators of soil quality must be better understood to devise effective management strategies. * Department of Soil Science, Punjab Agricultural University, Ludhiana 141004, Punjab, India PROPERTIES OF BIOCHAR The chemical properties of biochar depend on the composition of the feedstock and by the production conditions, including heating rates, final temperatures, and duration of heating (residence time). A number of studies have investigated the influence of the type of feedstock and conversion technology employed on biochar properties (Li and Zhang 2005; Novak et al. 2009; Lee et al. 2010; Cantrell et al. 2012; Fabbri et al. 2012; Ronsse et al. 2013). For example, increase in pyrolysis temperature from 400oC to 600oC decreased the volatile and N components of biochar, and increased ash and fixed carbon content. Thus, biochar