SOIL PHYSICAL-PROPERTIES AS AFFECTED BY GRAIN CART TRAFFIC

Changes in soil physical properties resulting from multiple passes of an 18 m3 single-axle grain cart with a 15.2 t axle load were measured one year after the traffic occurred. Air permeability, air-filled poro sity, and dry density data were analyzed to determine how the soil res ponded to grain cart traffic and pre- and post-traffic tillage. Four r epeated passes of the cart decreased air-filled porosity and permeabil ity by as much as 50% in the 200- to 400-mm depth range when compared to the effect of a single wheel pass. With pre-traffic chisel plowing to a depth of 200 mm, most of the compaction in the 100- to 200-mm dep th occurred on the first pass. However, four repeated passes had a gre ater effect on soil properties in the plots that received no tillage c ompared to the plots that were chiseled before trafficking.