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Title: WATER-STABLE AGGREGATION AND ORGANIC MATTER IN FOUR SOILS UNDER CONVENTIONAL AND ZERO TILLAGE

Author
item Franzluebbers, Alan
item ARSHAD, M - AGRICULTURE & AGRI-FOOD

Submitted to: Canadian Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Aggregation is important in protecting soils from the destructive forces of water and wind erosion, which can deteriorate soil hydrologic and nutrient cycling properties leading to reduced production potential and environmental degradation. Successful development of land management strategies to improve soil quality requires physical and biochemical characterization of the processes of accumulation and compartmentalization of soil organic carbon in previously cultivated and degraded soils. Coarse-textured soils could be effectively managed with zero tillage to improve aggregation to a depth of 125 mm. Soil organic carbon sequestration with zero tillage compared with conventional tillage occurred only in water-stable macroaggregate fractions to a depth of 125 mm. Sequestration of soil organic carbon in macroaggregates with zero tillage was greater in coarse-textured soils than in fine-textured soils. Zero tillage in this cold semiarid climate on northern Alberta and British Columbia appears to have beneficial impacts on aggregation and soil water conservation, but little immediate impact on soil organic carbon.

Technical Abstract: Zero tillage management reduces soil exposure and disturbance and, therefore, may improve soil aggregation and organic matter sequestration under some environments. We determined the distribution and soil organic C (SOC) content of five water-stable aggregate (WSA) classes at depths of 0-50, 50-125, and 125-200 mm in a loam, silt loam, clay loam, and clay soil managed for 4-16 yr under conventional shallow tillage (CT) and zero tillage (ZT) in northern Alberta and British Columbia. Macroaggregation (>0.25 mm) and mean weight diameter (MWD) were greater under ZT than under CT in coarse-textured soils at a depth of 0-125 mm. Under CT, macroaggregation and MWD increased with increasing clay content, thereby reducing the potential of ZT to improve these properties in high clay-content soils. Concentration of SOC tended to be greatest in macroaggregates and lowest in microaggregates of coarse-textured soils, but was not different among WSA classes of fine-textured soils. Soil organic C content of macroaggregates under ZT was 0.34, 0.40, 0.62, and 0.16 kg/m2 greater than under CT at a depth of 0-200 mm in the loam, silt loam, clay loam, and clay soil, respectively.