Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/19/1996
Publication Date: N/A
Technical Abstract: Zero tillage reduces soil exposure and disturbance and therefore, may improve soil aggregation and organic matter sequestration under some environments. We determined the mass, soil organic C (SOC), soil microbial biomass C (SMBC), and respiratory activity in five water-stable aggregate classes at depths of 0-50, 50-125, and 125-200 mm of four soils (loam, silt loam, clay loam, and clay) managed for 4 to 16 yr under conventional shallow tillage (CT) and zero tillage (ZT). Macroaggregation (>0.25 mm) and mean weight diameter were greater under ZT than under CT in coarse-textured soils at a depth of 0-125 mm. Carbon mineralized in 24 d and SMBC were an average of 9% greater under ZT than under CT in macroaggregates. However, C mineralized and SMBC in whole soil were 6% lower under ZT than under CT due to a redistribution into microaggregates. Macroaggregate-protected SOC to a depth of 200 mm was an average of 67 kg/ha under CT and 98 kg/ha under ZT, ranging from 0.1-7% of SOC. Our results suggest that implementation of ZT in this cold semiarid climate can quickly improve water-stable aggregation of coarse-textured soils and more slowly increase SOC sequestration and active soil C pools whenever macroaggregation is improved.