Abstract

ESPINOZA, Yusmary. Effect of tillage on organic matter and soil aggregates in a maize cropped tropical agroecosystem. Bioagro [online]. 2010, vol.22, n.3, pp.177-184. ISSN 1316-3361.

The effect of tillage systems were evaluated on different pools of C and N in soil and their distribution and turnover time in soil size fractions of a maize cropped field. Soil samples were incubated to determine mineralizable C and N. Previously, C and N microbial biomass, and total C and N were determined. Samples were also separated into different aggregate sizes by wet sieving, and δ¹³C analyzed. In general, cropping corn with conventional tillage (LC) and minimum tillage (ML) increased recalcitrant C and N of the soil, but decreased the labile fraction of C as microbial and nonmicrobial biomass, as compared with the no-tillage system (SD). After 8 years, the largest aggregate sizes (>250 μm) increased by 8 % under SD, decreased by 10 % under LC, and showed no changes under ML. The smallest amount of sequestered C was observed in the microaggregates (means of 2.94 kg·m^-2) compared to macroaggregates (4.2 kg·m^-2). The organic matter turnover time was higher for ML and LC as compared to SD. Under the conditions of this study, it was found that storage of C in tropical soils can be possible by the adoption of proper management techniques, such as a no-tillage system.

Keywords : Minimum tillage; microbial biomass; carbon sequestration; organic matter turnover.