Stratification ratio as soil carbon sequestration indicator in macroaggregates of Oxisol under no-tillage/Relacao de estratificacao como indicador do sequestro de carbono em macroagregados de Latossolo sob plantio direto

The decrease in soil organic carbon (SOC) content in deeper layers indicates the occurrence of stratification between the surface layer and subsurface layer of soil due to continuous C addition by crop residues. The objective was to evaluate the change (delta) of stratification (RE) of carbon (C) as an indicator of C sequestration and soil total and particulate soil in macroaggregates of two soils (Typic Hapludox) with different textures, managed in no-tillage system. The tests were developed in completely randomized design twelve repetitions. Analyzed factors were: (a) two soils: Oxisol with medium texture and Oxisol with clay texture, (b) sampling depth: 0-5 and 5-20cm, (c) two sampling times (October 2007-[T.sub.1], September 2008-[T.sub.2]). The results were submitted to variance analysis by program SISVAR 5.3, using the Tukey test at 5% significance. There was a significant linear relationship between the Δ RE and carbon sequestration rate total macroaggregates Oxisol with medium texture ([R.sup.2]=0.78 **) and Oxisol with clay texture ([R.sup.2]=0.81 **) indicating that there was C sequestration confirming to be a sensitive indicator of the rate of C sequestration in soil macroaggregates.