Adoption of Conservation-till, No-till, and Intensified Cropping in Washington's Winter Wheat-Summer Fallow Region.

The tillage-based winter wheat (Triticum aestivum L.) – summer fallow (WW-SF) cropping system has dominated dryland farming in the low-precipitation (< 300 mm annual) region of the Inland Pacific Northwest for 120 years.  Traditional tillage practices used during fallow are intensive and often leave the soil vulnerable to wind erosion.  Numerous long-term cropping systems studies have been conducted to find profitable and environmentally sound alternatives to traditional practices.  The undercutter method of WW-SF farming uses non-inversion tillage with a wide-blade V-sweep plus fertilizer injection followed by one to three rodweeding operations.  This method generally results in 30% or more residue cover retained on the surface throughout the fallow period and has been successfully adopted by more than 50 growers.  No-till summer fallow has not been popular with growers because, compared to tilled fallow, late-August planting of winter wheat is generally not possible due to loss of water in the seed zone.  However, late-August planting is frequently not feasible even with tilled fallow in the driest portion of the region and there is a renewed research effort to identify conditions suitable for no-till fallow based on soil water content in April.  Recrop (i.e., no summer fallow) spring wheat and spring barley can be grown profitably with as little as 280 mm annual precipitation but timing of precipitation is critical.  A spring cropping decision model was recently developed to help growers determine the yield potential of spring wheat based on over-winter precipitation stored in the soil plus expected April, May, and June rainfall.