Improved Management Practices in Grasslands Can Alter the Biogeochemical Processes and Carbon Storage in Spodosols.

A significant amount of native rangeland and woodland has been converted to improved pastures by adopting improved management practices (IMP). These alterations of land use can affect the quantity and quality of soil carbon (C). There is growing interest in understanding the mechanisms and pathways of microbial mediated decomposition of soil organic matter in grasslands as affected by IMP. Most of the previous studies analyzing the effects of IMP in grasslands on soil biogeochemical process have mostly concentrated on the top soil (0-30 cm) which also includes the microbially active soil depths. The sub-surface spodic horizon also stores a large amount of C but not much is known about how the IMP influence the microbial and biogeochemical processes in deeper soils. The objectives of this research were to i) evaluate the effects of IMP on soil biogeochemical processes ii) determine the potential of the spodic horizon to store C. The experimental site consisted of two management systems including improved pasture and native rangeland. The IMP consisted of improved grazing and the addition of inorganic fertilizer and non-woody perennial grass species. The data from this study indicated that IMP resulted in increased soil organic C (SOC) stocks from 31 Mg ha^-1 in native rangeland to 63 Mg ha^-1 in improved pastures with the majority (10 Mg ha^-1 in native rangeland and 24 Mg ha^-1 in improved pastures) of C being stored in the spodic horizon. Moreover, improved pastures increased the microbial biomass carbon (MBC) and activity of extracellular enzymes involved in C and N mineralization compared to native rangeland system. The increased activity of beta-glucosidase enzyme was found to be well correlated with the SOC concentration (r = 0.90), MBC (r = 0.79), TN ratio (r = 0.96), and hot water-extractable C (r = 0.85) suggesting that the quality and quantity of C substrate play an important role in microbial mediated decomposition of Soil organic matter. Therefore, improved management practices can be helpful in storing more C in soil along with supporting cattle industry.