Title: THE EFFECT OF PRECIPITATION VARIATION ON SOIL MOISTURE, SOIL NITROGEN, NITROGEN RESPONSE AND WINTER WHEAT YIELDS IN EASTERN OREGON

The semi-arid regions of the Pacific Northwest are characterized by a high degree of annual temperature and precipitation variation. As a result of this climatic variation, dryland nitrogen fertilizer trials on fallow-,wheat rotations typically demonstrate a variable response. Wheat growers in the area must not only cope with this climatic variation and its sundry effects upon their livelihood, they must also make decisions regarding the future level of anticipated climatic variation. The specific objectives were to: 1) develop a climati-cally responsive yield potential prediction model for soft white winter wheat from historical data at the Sherman Branch Experiment Station (Moro, OR); 2) modify this model for use on commercial fields; 3) field simulate five fallow-crop precipitation patterns characteristic of the variation found in the Sherman county area of eastern Oregon in orde