Submitted to: Western Nutrient Management Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/24/1997
Publication Date: N/A
Interpretive Summary: Wheat grown in the Pacific Northwest often needs additional plant nutrients to produce optimum yield. It is important to apply nutrients only when needed to avoid adverse environmental effects and unnecessary production costs. This study investigated the need for major nutritional elements such as nitrogen, phosphorus, and sulfur, micronutrients such as zinc and copper, fungicides to control root diseases, and methanol as a growth stimulant for winter wheat grown without irrigation. Studies were conducted for two years across four agronomic zones ranging from 10 to 19 inches of annual precipitation. Nitrogen increased yield by 12-95% when spring rainfall was above normal, but only 0-5% when spring rainfall was below-normal. None of the sites needed additional phosphorus, sulfur, or micronutrients to produce optimal yield. Wheat at one of eight sites responded to fungicides, and none responded to methanol. Because nitrogen had the greatest influence on yield, most emphasis should be given to selecting the nitrogen rate that best meets environmental conditions. Other nutrients need only be applied if a deficiency is documented by repeated field tests.
Technical Abstract: Fertilizer can increase wheat yield substantially in the Pacific Northwest, but any increase is affected by drought stress, cropping history, and past fertilizer practices. It is important to apply nutrients only when needed to avoid adverse environmental effects and unnecessary production costs. This experiment consisted of four nitrogen (N) rates along with comparisons to evaluate the need for phosphorus, sulfur, micronutrients, fungicides, and methanol to produce optimal dryland winter wheat yield. The experiment was conducted for two years in each of four agronomic zones ranging from 10 to 19 inches annual precipitation. Nitrogen response was strongly related to adequacy of spring precipitation. Little N response occurred when spring precipitation was low, but up to 120 pounds N per acre was required to maximize yield when spring precipitation was high. Winter wheat did not respond to phosphorus, sulfur, or micronutrients, indicating that supply from soil and past application practices was sufficient. One of eight sites responded to fungicide application, and none to methanol. Because N had the greatest influence on yield, most emphasis should be given to selecting the N rate that best meets environmental conditions. Other nutrients need only be applied if a need is documented by repeated field tests.