The Willamette Valley is generally Z8 but surrounded by hills and mountains. This is what moderates the weather here. We seldom get snow, but travel just a few miles to the east towards the Cascade mountains and the story is quite different. The soil is slightly acidic, and depending on the crop, some farmers lime their fields.
The geology is quite interesting in that the soil is not an effect of the Willamette River flooding over time, but from massive floods originating in Montana and carrying silt all across Eastern Washington, down the Columbia River and up the Willamette Valley. There were many floods dating to the last ice age ("Bretz floods) and they occurred during warming periods when ice dams holding back Lake Missoula broke in cataclysmic events. To make a long story short, the soil here arrived from places quite far away!
