|Baumhardt, Roland - Louis|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2001
Publication Date: 4/1/2002
Interpretive Summary: Dryland winter wheat and grain sorghum are grown on the semiarid North American Great Plains using the wheat-sorghum-fallow crop rotation. In this rotation, stubble-mulch (SM) or no-till (NT) reduces evaporation and increases yield, but NT plots compact and increase runoff compared to SM. We tested paratill (PT), a residue saving chisel plow, effects on soil density (SD), penetration resistance (PR), and infiltration. About 8 month after PT (before planting wheat), we measured infiltration of simulated rain applied at 2 in/hr into NT or SM contour-farmed level-terraced watersheds. Infiltration increased from 1.5" for SM to 0.75" for NT. Paratill did not significantly increase infiltration amount, i.e., infiltration with PT was 1.05" compared to 1.1" without PT. Measured PR and SD showed that PT loosened the soil and reduced PR and SD with depth for NT, but sweep operations reconsolidated PT soil. We conclude that PT did not increase rain infiltration into the Pullman clay loam soil with either SM or NT residue management, because the formation of soil surface crusts rapidly regulated infiltration. Sweep tillage operations used with SM rapidly negated PT benefits to reduce SD and PR.
Technical Abstract: Dryland winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are grown on the semiarid North American Great Plains using the wheat-sorghum-fallow (WSF) crop sequence. No-tillage (NT) or stubble mulch tillage (SM) reduces evaporation when used with WSF and increases yields. However, soil consolidation with NT increases runoff compared to SM. We measured soil density (SD), penetration resistance (PR), and infiltration of rain about 8 months after paratill, PT, (before planting wheat) on either NT or SM managed Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll). Subplots in six contour- dryland farmed level-terraced watersheds cropped using a WSF rotation and NT or SM management were paratilled to a 0.35-m depth at 0.75-m intervals after sorghum harvest. Infiltration amount was 32.4 plus or minus 3.9 mm for SM compared with 21.9 plus or minus 2.5 mm for NT. Infiltration was not significantly increased by PT, i.e., infiltration with PT was 26.7 plu or minus 5.7 compared to 27.5 plus or minus 7.4 mm without PT. Paratill reduced PR with depth compared to NT, but the SM sweep operations consolidated PT soil. We conclude that PT did not increase infiltration into SM or NT managed clay loam because rain infiltration was regulated by the formation of a surface crust. Sweep tillage operations used with SM rapidly negated PT benefits to reduce SD and PR.