SOIL ORGANIC C IN THE TALLGRASS PRAIRIE-DERIVED REGION OF THE CORN-BELT - EFFECTS OF LONG-TERM CROP MANAGEMENT

Concerns with rising atmospheric levels of CO2 have stimulated interes t in C flow in terrestrial ecosystems and the potential for increased soil C sequestration. Our objectives were to assess land management ef fects on soil organic carbon (SOC) dynamics and SOC sequestration for long-term studies in the tallgrass prairie region of the US. Major los ses of SOC following conversion of native prairie to arable agricultur e at Sanborn Field and the Merrow Plots were rapid (20 to 40 yr), occu rred in response to greatly reduced C inputs and accelerated C decay r ates, and had largely abated by the mid-1900s, Losses of SOC occurred mainly in easily decomposable, labile C fractions. At Sanborn Field, m odeled labile SOC was reduced to 4% of native prairie levels for treat ments with low C inputs. A large capacity for soil C sequestration lik ely exists in the tallgrass prairie region, if labile C pools can be r eplenished. This agroecosystem has a strong C decomposition regime and increased sequestration of labile C will rely on management practices that increase C inputs (i.e,, fertilization, returning crop residues) and stabilize labile C (i,e,, perennial cropping, reduced tillage). T he capacity for soil C sequestration, however, will vary considerably among sites and be dependent on initial levels of labile SOC and the a bility of management practices to stabilize greater inputs of labile C . (C) 1998 Published by Elsevier Science B,V, All rights reserved.