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Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

Abstract

1. Five types of injury were inflicted on oats, barley and winter wheat at weekly intervals from May 11 to July 6.

2. Complete destruction of above ground parts increased the percentage of injury from 10 percent for oats, 43 percent for barley and 70 percent for wheat on May 11 to total loss for oats on June 15, barley on June 8 and wheat on June 1.

3. Cutting off all leaves above the growing point reduced yields about in proportion to the percentage of leaf area removed at each weekly interval.

4. Whipping severely enough to break all plants resulted in increasing the percentage of injury for oats from 10 percent on May 11 to 69 percent on June 15, for barley from 22 percent on May 11 to 72 percent on June 15, and for wheat from 25 percent on May 11 to 77 percent on June 15.

5. Bruising the developing heads before they had emerged reduced the yield of oats 10 percent on June 8, 8 percent on June 15 and 10 percent on June 22. Barley yields were reduced 25 percent as a result of this injury when inflicted on June 8, 10 percent on June 15 and 51 percent on June 22. Wheat yields were reduced 9 percent for May 25, 10 percent for June 1, 13 percent for June 8 and 20 percent for June 15.

6. Bruising the heads apparently increased the amount of sterile spikelets but was not the only cause of this condition.

7. Breaking the stems about the middle, so that the heads hung straight down, reduced yields progressively less from early in June until the grain was mature. Yields of oats were reduced at succeeding weekly intervals from June 8 to July 6, 47 percent, 37 percent, 31 percent, 24 percent and 12 percent, respectively, and barley for the same periods, 50 percent, 28 percent, 28 percent. 12 percent and 11 percent. This injury to wheat at weekly intervals from June 1 to June 29 reduced yields 44 percent, 42 percent, 31 percent, 14 percent and 8 percent, respectively.

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