Roots and Residues: Soil Organic C and Soil Food Web Dynamics In Both Perennial and Annual Production Systems In Kansas.

Systems capable of supporting high yields over long periods of time while receiving few external inputs and maintaining robust ecosystem services are a constant goal for sustainable agriculture.  In Kansas, researchers have identified a group of unfertilized, annually harvested tallgrass prairie meadows (PM) that have demonstrated the ability to sustain greater annual exports of biomass than adjacent wheat fields (AG) on similar soil types for approximately 80 years, without receiving fertilizer inputs.  These PMs also support soil organic C (SOC) pools and nematode food webs similar to natural ecosystems.  It is hypothesized that the extensive perennial root systems of the PMs may be a key factor in their ability to continually sustain both biomass harvests and the soil ecosystem.  This study seeks to: 1) Quantify the root systems present in both PM and AG sites, 2) Estimate SOC pools and turnover in both active and stable fractions in PM and AG sites, and 3) Elucidate the relationship of roots to both SOC pools and nematode food webs.  

Soil core samples were collected to a depth of 1m in May and June of 2008.  Soil samples were analyzed for SOC, total soil nitrogen (TSN), microbial biomass C (MBC), nematodes, and a particle size fractionation of SOC in coarse sand (>250μm), fine sand (250-53μm), silt (53-2μm), and clay (<2μm) sized fractions.  Root biomass, root length and root C were also analyzed to a depth of 1m.

PM sites contained five times more root biomass (5463 kg ha^-1 in PM and 907 kg ha^-1 in AG) in the soil surface layer (0-10cm) and significantly greater root biomass and length to 1m than AG sites.  PM sites also demonstrated significantly larger SOC pools in all fractions measured to a depth of 60cm.  Further, data analysis also suggests that roots are a key factor in both SOC fractions and nematode food webs at these sites.