Hydraulic properties in a silt loam soil under natural prairie, conventional till, and no-till

Tillage in the Palouse region of Washington State over the past 100 yr has influenced the soil physical and biological properties. In particular, hydraulic properties are significantly affected by soil cultivation. The objectives of this study were to assess the temporal patterns of soil hydraulic properties under three management systems, natural prairie (NP), conventional till (CT), and no-till (NT), and to compare hydraulic properties between these three systems. Saturated and near-saturated hydraulic conductivities (up to -15 cm-H2O hydraulic head), and soil water retention curves were determined using intact soil cores taken from the top 10 cm of soil. Soils were sampled at six different times during a period of 1.5 yr from a NP, a longterm (>100 yr) CT, and a 27-yr-old NT system. The NP represented the original soil and natural vegetation of the area. Significant temporal variation in hydraulic conductivity was found. Temporal variation was most evident in the NP soil, where organic matter content was twice as large as under the CT and NT soils. Hydraulic conductivities in the NP were about one order of magnitude larger than in the cultivated soils. In NT, saturated hydraulic conductivities in the top 5 cm of soils were significantly larger than in CT. No-till and CT soils had similar near-saturated hydraulic conductivities, indicating that even 27 yr of continuous NT could not restore the original hydraulic properties of the soil. Restoration of original hydraulic properties in cultivated former prairie soils may take considerably longer.