Tuesday, November 14, 2006

Aggregate Stability: Influence of the Chemical, Physical, and Biological Mechanisms in three Different Soil Types.

Karina Fabrizzi1, Charles Rice2, Telmo Amado3, Jackson Fiorin4, Pedro Barbagelata5, and Ricardo Melchiori5. (1) Kansas State Univ., 2004 Throckmorton Plant Sciences Center, Manhattan, KS 66506-5501, (2) Kansas State University, Dep. of Agronomy, 2701 Throckmorton Hall, Manhattan, KS 66506-5501, (3) Soil Department, Federal Unversity of Santa Maria, Santa Maria, Rio Grande do Sul, 97119-900, Brazil, (4) FUNDACEP, RS 342 km 149, Cruz Alta, RS, 10-98100-970, Brazil, (5) INTA Parana, Ruta 11 km 12.5, Oro Verde, Entre Rios, 3100, Argentina

The objective of this research was to determine 1) the relative importance of the chemical, physical and biological mechanisms on aggregate stability in three different soil types and 2) the effect of management practices on these mechanisms of aggregate formation. Soil samples were taken from 0-5 cm from three soils: a Mollisol (Kansas, USA), an Oxisol (Brazil), and a Vertisol (Argentina). All three sites included native prairie, and no-till and tilled cropping systems. Soil samples were incubated at 25ºC. Evolved CO2-C was measured every 2 days during the first month, and weekly thereafter. Throughout the 120 d incubation period aggregate size distribution was determined by wet sieving and separated into >2000, 250-2000, 53-250, and 20-53 μm aggregate-size classes. Total C and N were determined by direct combustion using a Carlo Erba C/N Analyzer. Microbial community composition was determined by phospholipid fatty acids (PLFA) technique. The C and N concentration of the individual aggregate size classes were also determined.