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Tillage has been associated with soil organic matter (SOM) decline. A case study of two adjacent farms was conducted in eastern South Dakota. One farm used no-till (NT) and the other used chisel tillage (CT). We hypothesized that soil under NT, compared with tillage, would have both greater quantity and greater quality of SOM and that this improved SOM condition would result in increased water stable aggregation (WSA). A rotary sieve was used to sort dry field aggregates into six size groups: 19 ram. Water stable aggregation, soil organic C (SOC), N, glomalin, and basidiomycete fungi were measured. Fine particulate soil organic matter (fPOM, 0.5-0.053 mm) and coarse particulate organic matter (2.0-0.5 mm) were isolated by sieving. Quantitative solid-state [sup.13]C nuclear magnetic resonance was used to determine C type in humic acid, humin, and whole soil. The fPOM/SOM ratio was greatest in Abbreviations: AM, arbuscular mycorrhizal; cPOM, coarse particulate organic matter; CT, chisel tillage; DPMAS, direct-polarization magic-angle spinning; EC, electrical conductivity; fPOM, fine particulate organic matter; HA, humic acid; IRTG, immunoreactive total glomalin; NMR, nuclear magnetic resonance; NT, no-till; POM, particulate organic matter; SOC, soil organic carbon; SOM, soil organic matter; TPOM, total particulate organic matter; WSA, water stable aggregation.