undergo this dramatic cyclic change in soil structure; although seasonal variations in hydraulic conductivities Tillage in the Palouse region of Washington State over the past occur through root development, earthworm activity, 100 yr has influenced the soil physical and biological properties. In particular, hydraulic properties are significantly affected by soil culti-and other natural processes such as freezing and thawvation. The objectives of this study were to assess the temporal pat-ing, or shrinking and swelling. terns of soil hydraulic properties under three management systems, Soil compaction can also alter hydraulic conductivity. natural prairie (NP), conventional till (CT), and no-till (NT), and to Soil compaction, mostly caused by wheel traffic, decompare hydraulic properties between these three systems. Saturated stroys large pores, thereby reduces saturated and nearand near-saturated hydraulic conductivities (up to Ϫ15 cm-H 2 O hysaturated hydraulic conductivities (Ankeny et al., 1990; draulic head), and soil water retention curves were determined using Heddadj and Gascuel-Odoux, 1999). The effects of soil intact soil cores taken from the top 10 cm of soil. Soils were sampled compaction vary with soil type and management. Under at six different times during a period of 1.5 yr from a NP, a longno-till systems, wheel traffic may cause compaction of term (Ͼ100 yr) CT, and a 27-yr-old NT system. The NP represented the soil matrix and results in reduction of saturated and the original soil and natural vegetation of the area. Significant temporal variation in hydraulic conductivity was found. Temporal variation near-saturated hydraulic conductivities, but biological was most evident in the NP soil, where organic matter content was effects, such as root channels and earthworm burrows twice as large as under the CT and NT soils. Hydraulic conductivities may counteract the compaction-induced reduction of in the NP were about one order of magnitude larger than in the the conductivities (Gantzer and Blake, 1978; Ankeny cultivated soils. In NT, saturated hydraulic conductivities in the top et al., 1990). 5 cm of soils were significantly larger than in CT. No-till and CT soils Because of the many factors affecting the hydraulic had similar near-saturated hydraulic conductivities, indicating that conductivity, a temporal pattern may be difficult to obeven 27 yr of continuous NT could not restore the original hydraulic serve (Logsdon, 1993). Sometimes, certain factors are properties of the soil. Restoration of original hydraulic properties in more dominant than others, allowing us to discern temcultivated former prairie soils may take considerably longer. poral patterns. For instance, saturated and near-saturated hydraulic conductivities can increase from a wet to dry season due to the formation of cracks, particularly
