4.3 Effect of grass-legume mixture on soil CO2flux
The decomposition of grass-legume mulch over 5-years of revegetation, influence microbial respiration and increased CO2 flux of the reclaimed waste dump by 19%. Soil CO2 flux attributed by natural forest was 1.5 times greater than the 5-years old reclaimed waste dump (Figure 8). Variation in the rate of soil CO2 fluxes can be due to the difference in soil temperature, litter/biomass input, and plant root growth (Frouz, 2017). Higher N concentration of the legume shoot and root residues showed an efficacious effect on soil N pool whereas higher root C in grass residue built soil C pool and increases CO2 efflux and their addition as mulch available for microbes increases the soil microbial respiration throughout the stages of decomposition. An increase in labile C pool would increase soil respiration as the grass biomass residues reduce N leaching i. e. positive priming effect (Frouz, Novotna, Cermakova, & Pivokonsky, 2020; Wu et al., 2020). Root biomass-derived C compared to shoot biomass C have been reported to contribute greater and relatively stable soil C pools (Ghafoor, Poeplau, & Katterer, 2017). Apparently, these differences gradually declined during microbial decomposition because soil C:N ratio decreased after 1-5 years of revegetation (Table 3). Liu et al. (2020) reported the benefits of legume biomass (Caragana korshinskii ) on the Loess Plateau of China showed greater potential to sequester soil C. Similarly, 7-years of perennial legume M. sativa, Lespedeza davurica, and Astragalus adsurgens growth increased the soil C sequestration of arable land by 79, 68 and 74% (Guan et al., 2016). The rate of CO2 flux, unlike other soil parameters, respond more quickly under varying soil temperature and the quality of organic matter to assess soil fertility (Ahirwal, Maiti, & Singh, 2017b; Munoz-Rojas, Erickson, Dixon, & Merritt, 2016) indicating whether the soil conditions are favorable for decomposition process in long term revegetation.