Influence of long-term tillage and crop rotations on soil hydraulic properties in the US Pacific Northwest

In the low precipitation zone (<0.3 m [11.8 in] annual precipitation) of the Inland Pacific Northwest, no-tillage continuous spring cereal and no-tillage spring cereal-chemical fallow rotations are being examined as alternatives to the traditional winter wheat-summer fallow rotation for soil conservation. There is limited information, however, regarding the long-term effects of no-tillage cropping systems on soil hydraulic properties in this semiarid region. The objective of this study was therefore to characterize infiltration, water retention, saturated hydraulic conductivity and bulk density of a silt loam that had been subject to various tillage and crop rotations in east-central Washington. Treatments examined included no-tillage spring barley-spring wheat (NTSB-SW), no-tillage spring wheat-chemical fallow (NTSW-ChF), and traditional winter wheat-summer fallow (WW-SF). Soil properties were measured in spring and late summer 2006 due to the vulnerability of the soil to rapidly dry and erode during these seasons. Saturated hydraulic conductivity was determined by the falling-head method, infiltration was measured using a double-ring infiltrometer, and water retention characteristics was assessed by examining the temporal variation of in situ soil water content. NTSB-SW resulted in higher infiltration and saturated hydraulic conductivity, lower bulk density, and larger and/or more continuous pores in the upper soil profile (<0.1 in [<3.9 in] depth) than WW-SF and NTSW-ChE Infiltration and saturated hydraulic conductivity were lower for chemical fallow than for traditional fallow in spring whereas hydraulic conductivity was lower for summer fallow than chemical fallow in late summer. Soil hydrologic properties appeared more favorable for no-tillage continuous spring cereal rotations. These results arc useful for soil and water management and conservation planning in the low precipitation zone of the Inland Pacific Northwest.