Soil organic matter dynamics and land-use change on Oxisols in the Cerrado, Brazil

Land-use change (LUC) from native vegetation to feedstock production is the main responsible for the losses of carbon (C) from soil organic matter (SOM) to atmosphere. We evaluated different land-uses common in the Cerrado with potential to restore SOM levels. We sampled soil (0.0-0.1; 0.1-0.2; 0.2-0.3; 0.3-0.4 m) from sites located in the municipality of Uruçuí (Piauí State, Northeast region of Brazil). Land-uses evaluated were: i) native vegetation (NV); ii) no-tillage over six years (NT6); iii) no-tillage over nine years (NT9); iv) Urochloa brizantha pasture over two years (PA2); v) U. brizantha pasture over six years (PA6); vi) Eucalyptus urophylla afforestation over six years (EU6); and vii) E. urophylla afforestation over twelve years (EU12). We determined soil C stocks, chemical (fulvic and humic acids) and physical (particulate and organic-mineral complexes) SOM fractions. Pasture was land-use that presented better results in terms to maintain C pools (recalcitrant and labile), consequently could restore soil C stocks. The no-tillage, due to the high difference between the results for the adoption times, was difficult to have an accurate interpretation if is effectively increasing the C stocks. On the other hand, Eucalyptus afforestation does not seem to be an efficient land-use when it comes to the restoration of SOM levels, at least under the current management practices as well as the soil and climatic conditions in the Cerrado.