Reconsolidation of a Torrertic Paleustoll after Tillage with a Paratill

Abstract

Paleustolls in the USA occur mainly in the central and southern Great Plains. Torrertic Paleustolls are extensive in the southern Great Plains, where Pullman (fine, mixed thermic Torrertic Paleustoll) is the dominant series. Pullman soils occur on ≈ 1.54 million ha. They have dense Bt1 and Bt2 horizons that are slowly permeable and restrict root penetration. Deep soil loosening can enhance water infiltration and root penetration, but surface residues should be retained for further water conservation purposes. These goals can be achieved by using one of several deep chisel, subsoiler, or Paratill implements. A Paratill is a slant-legged implement that loosens a soil without inverting it. Paratill (PT) treatments were imposed on different notillage areas of Pullman soil in 1987, 1988, 1989, and 1990 at shallow (0.15–0.20m) and deep (0.25–0.30m) depths. Sweep tillage to a 7− to 10 − cm depth and no-tillage were other treatments. A given area received the Paratill and sweep tillage treatments only once in the 4-yr period. After imposing the treatments, no-tillage was uniformly used on all areas. In May and December 1990, bulk density (Db) was determined to 0.60 − m depths in all plots. Penetration resistance (PR) and water content were determined in May 1991. Deep PT resulted in the lowest mean Db, but there was no definite trend indicating that time since performing PT had an effect on the results. The PR results were similar to the Db results, and there was not a close inverse relationship between soil water content and PR. Based on this study, the rate of return of Pullman soil to its original condition following PT cannot be predicted.