Abstract:
In a series of 30 winter wheat fertilizer experiments conducted in the
Willamette Valley between 1963 and 1969, optimum rates of nitrogen fertilization
varied from 75 to 150 pounds per acre. Fertilization with N, particularly
at the-higher rates, increased the protein content of the grain.
Spring-applied N gave greater yield increases than fall-applied N and, with
only one exception, no advantage was gained from applying a portion of the
N fertilizer in the fall. Split N applications in the spring gave no advantage
over a single spring application of N. Grain yield responses to phosphorus
fertilization were obtained at most sites where soil-test levels for P were
below 20 ppm. Potassium fertilization increased the yield of grain at one location
where the soil-test value for K was 55 ppm. Grain yield response to sulfur
fertilization was obtained at only one of the sixteen locations where the effect
of S fertilization was measured. Lime applications increased grain yields at
two sites located on strongly acid soils.
Three different wheat varieties were included in these experiments.
Nugaines outyielded Druchamp on the valley floor soils and Druchamp was
superior to Nugaines on the acid hill soils. Yamhill usually outyielded the
other two varieties on both hill soil and valley floor soil locations.
