Windblown dust affected by tillage intensity during summer fallow

Abstract

Abstract Winter wheat–summer fallow is the conventional crop rotation used on more than 1.5 million ha of agricultural land in the low precipitation zone of the Columbia Plateau in the Pacific Northwest United States. This land is very susceptible to wind erosion during summer fallow because multiple tillage operations during fallow degrade and expose the soil to high winds. We examined possible alternatives to conventional tillage for reducing the emission of windblown PM10 (particulate matter ⩽10 μm in aerodynamic diameter) during summer fallow. Soil was subject to seven (conventional), five (reduced), three (delayed-minimum), and zero (no) tillage operations between harvest in July 2004 and sowing in August 2005. Sediment catch and PM10 concentration and wind speed profiles were measured after each tillage operation and sowing under simulated high winds (using a portable wind tunnel) to estimate horizontal sediment and PM10 flux. Horizontal sediment and PM10 flux generally decreased with a decrease in number or intensity of tillage operations. No tillage resulted in the lowest sediment and PM10 flux after most tillage operations; no tillage, however, is not yet an economically viable management option for the region. Sediment and PM10 flux were typically lower for reduced and delayed-minimum tillage than for conventional tillage. Our study suggests that PM10 flux can be reduced from agricultural soils during the summer fallow phase of a wheat–fallow rotation by using reduced or delayed-minimum tillage practices. The reduction in PM10 flux from soils will improve air quality during high winds in the region.