Native prairie and winter wheat pastures are among the primary resources used to graze cattle in central Oklahoma. These forage resources are subject to numerous stressors that affect land condition including grazing, climate, soil fertility, and farming operations. Understanding responses of soil characteristics to management is crucial to sustainable use of these resources. This study compared soil responses of an upland site in central Oklahoma to 26 y (1977-2003) of different forms of sustained management applied to 1.6 ha experimental paddocks situated along a common slope. Included were grazed, conventionally tilled winter wheat and three forms of management applied to paddocks of tallgrass prairie (light stocking rates over long grazing periods, high stocking rates over short grazing periods, and not grazed). Soil cores to 0.25 m depth were collected from paddocks under each form of management at 1.5 m intervals along 150 m transects (n=101 per paddock) situated between the ridge and toe slope, and divided into 3 segments (0-0.05 m, 0.05-0.10 m, and 0.10-0.25 m depths). Soil bulk density and organic matter (OM) concentrations were determined, variogram analyses defined distribution patterns, and distribution maps were developed.

Results/Conclusions

Soils of grazed wheat pasture were 13% denser and contained 21% less OM than soils in the native prairie paddocks. Management effects on native prairie were largely confined to the upper 0.05 m of soil, with 9% denser soils under intensive management, while OM concentrations were similar across type of management. Intensive forms of management also tended to produce more simplified distribution patterns. Responses indicated patch-scale organization of soil characteristics in wheat and native paddocks differed after 26 y, which may alter landscape function.