Evaluation of Soil Recompaction by Transverse Wheeling of Tillage Slots

Narrow, gypsum‐enriched slots are a technique for ameliorating texture‐contrast soils (Natrixeralfs) in Australia. It is expected that undisturbed soil adjacent to the slots will protect loosened soil within the slot from recompaction by wheel traffic. Vertical stresses in slots were compared to those in troughs formed by ripping, and to the stresses between slots and ripping troughs. Stresses were smaller in slots than outside, unless increased by downward movement of the whole slot contents. Inside troughs the stresses were similar to those outside. Macrostructure after zero, one, or four wheelings was also measured. There was more increase of density and loss of macroporosity in ripping troughs than in slots. However, the macrostructure in the slots could be seriously damaged after four consecutive passes over soil at water contents near the lower plastic limit. Thus gypsum‐enriched slots provide only a limited amount of protection from compaction and the amelioration technique needs to be associated with suitable techniques for the management of subsequent traffic.