Macroaggregates Carbon Storage Potential in Brazilian Oxisol Under Long-Term No-till.

In long-term no-till associate with cropping systems to keep the soil permanent covered leads to stimulate the macroaggregation and increase carbon (C) storage. However, the potential of C storage in macroaggretes has a lack of knowledge in terms of the relationship between texture and soil organic carbon fractions. The aims of this study was to assess the potential of C storage in the labile and mineral associated organic C (MAOC) in response to no-till systems under an Oxisol with two texture classes. The experimental design was a 2x2x2 factorial with 12 replicates. The factors analyzed were: 1) An Oxisol with two textural class such as: sandy-clay and clay; 2) two sample time: T1 - October of 2007; T2 - September 2008; 3) two sampling depths: 0-5 and 5-20 cm layer. The aggregates were obtained by wet sieving and obtaining six classes: 19-8, 8-4, 4-2, 2-1, 1-0.5 and 0.5-0.25 mm. The C content in all samples was determined by dry combustion using an elemental CN analyser (TruSpec LECO). The soil mass of aggregates size of 8-19 mm represented 86.0 and 84.9 % of all classes in the sandy-clay and clay texture respectively. A close linear relationship was obtained between C sequestration rate and the soil C stratification ratio such as Rē=0,78** and Rē=0,81**e for sandy-clay and clay, respectively. Our results support that the stimulation of macroaggregation is the main way to sequester C.