Year: 2000
Type: dissertation
Abstract: Soil C sequestration in agricultural ecosystems is an immediate and significant option to mitigate the increase in the atmospheric CO 2 concentration.The objectives of this study were to determine 1) the influence of crop and soil management practices applicable to Kansas (i.e., tillage, N fertilization, and crop rotations) on soil C and N, C sequestration rates, soil aggregation and aggregate-associated C and N; and 2) the influence of long-term tillage practices on SOC and total N, soil aggregation and aggregate-associated C and N in three soil types: an Oxisol (Brazil), a Vertisol (Argentina), and a Mollisol (Kansas, USA).The Kansas experiments included: tillage (conventional tillage (CT), reduced tillage (RT) and no-tillage (NT)) and native prairie; nitrogen (N) fertilization rates; and crop rotations comprising various combinations of winter wheat (Triticum aestivum L.), grain sorghum (Sorghum bicolor L. Moench), and soybean (Glycine max L. Merrill).The presence of a fallow period negatively affected C sequestration rates even under NT systems.Nitrogen fertilization generally increased C sequestration rates.Rotations that contained wheat or sorghum had the greatest C sequestration rates while continuous soybean had the lowest rates.Cultivation decreased the amount of macroaggregates with a concomitment increased in the amount of microaggregates.Wheat and sorghum increased total C in the macroaggregate fraction (>250 μm) under NT while soybean had the lowest C concentration.Cultivation reduced microbial biomass C and N and potentially mineralizable C and N. The combination of conservation tillage and rotations that produced a greater amount of residue had greater C sequestration rates.In the Oxisol, NT had greater amounts of large macroaggregates (>2000 μm) than CT, however no differences between tillage practices were detected in the Vertisol and Mollisol.Cultivation of native grassland reduced the amount of macroaggregates and the associated C and N concentration; however NT tended to be more similar to the native grassland.Overall, our results indicated that the use of conservation tillage could be an important strategy to sequester C in these agroecosystems.The adoption of management practices that enhance C sequestration would be important for reducing GHGs emissions and maintaining the sustainability of agricultural systems.
Author: Karina Paola Fabrizzi
Language: English
Subfield: Soil Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2265452078