Submitted to: Pendleton Station Field Day
Publication Type: Experiment Station
Publication Acceptance Date: 4/12/1995
Publication Date: N/A
Technical Abstract: Well-run long-term experiments (LTEs) that utilize up-to-date technology allow us to track changes in crop yield over time. When conducted in the same location, many extraneous factors are removed and only those inherent to the original land selection or that develop internally remain as a deterrent to proper interpretation. Several LTEs have been conducted at Pendleton since the 1930's that include winter wheat grown in wheat/fallow (WF), wheat/pea (WP), or wheat/wheat (WW) rotation. Winter wheat yield has risen steadily since the 1930's in all rotations, with a greater rate of increase since semi-dwarf wheat was introduced in the mid 1960's. Average yield change for the above rotations from 1940 to 1990 has been 45 to 78, 30 to 63, and 20 to 55 bushels/acre, respectively. Yearly yield is affected by precipitation level, with growing-season (April 1-June 30) rainfall having much greater influence than overwinter (September 1 to March 31) precipitation. Annual-crop rotations (WP, WW) are much more affected by precipitation than is the WF rotation. Semi-dwarf wheat varieties grown since 1965 respond much more readily to precipitation than did the medium-tall varieties grown from 1931 to 1964. There is, however, still a wide scatter in yield after removing precipitation effects, indicating that many other factors such as disease, stand adequacy, etc. also contribute to yearly crop yield.