Roots are important organs that supply water, nutrients, hormones,
and mechanical support (anchorage) to crop plants and, consequently, affect
economic yields. In addition, roots improve soil organic matter (OM) by
contributing to soil pools of organic carbon (C), nitrogen (N), and microbial
biomass. Root-derived soil C is retained and forms more stable soil aggregates
than shoot-derived soil C. Although roots normally contribute only 10%–20% of
total plant weight, a well-developed root system is essential for healthy plant
growth and development (Fageria, 2013).
systems of crops play a vital role in improving soil health. Below-ground
biomass often referred to as ‘root biomass’ is considered as one of the most
relevant parameters of plant system on account of its significant role in
maintaining soil organic carbon in response to environmental changes (Hirte et
al., 2017). Below-ground biomass is an important carbon pool for many
vegetation types and land-use systems and accounts for about 20% (Santantonio
et al. 1977) to 26% (Cairns et al. 1997) of the total biomass. Below-ground
biomass accumulation is linked to the dynamics of above-ground biomass. The
greatest proportion of root biomass occurs in the top 30 cm of the soil surface
(Bohm 1979; Jackson et al. 1996).
biomass is defined as the entire biomass of all live roots, although fine roots
less than 2 mm in diameter are often excluded because these cannot easily be
distinguished empirically from soil organic matter (Anon., 2008). Live and dead
roots are generally not distinguished and hence root biomass is reported as
total of live and dead roots; and also the presence of extraneous organic
matter in soil including dead roots from previous crops, weed roots,
incorporated above ground plant residues and organic soil amendments, or
remnants of soil fauna (Hirte et al., 2017).
biomass accumulated below the ground acts like a store house of carbon. Generally
the amount of carbon stored in soil represents the balance between above ground
shoot dry matter and below ground root biomass production, root exudates and
their microbial decomposition. In this review an attempt has been made to
provide an overview on the contribution of root biomass in maintaining rhizosphere
soil carbon status and their association with microbial activity.