Evaluation of some morphological characters of corn in respect to their use in forecasting yield

The inter-relationships between certain measurable morphological plant characters and also the relationship of these characters before maturity with final yield in bushels per acre were investigated. From a study of the inter-relationships of morphological characters at Ames, Iowa, in 1940, the following were shown to be highly correlated: Leaf height and ligule height; plant height increase and dry weight increase up to flowering; and actual leaf area and estimated leaf area. It was suggested that the distance from the soil surface to the ligule of the upper leaf was a sufficiently accurate measure of plant height. Using the formula developed for the purpose, leaf area measurement made on the upper, lower, and center leaves of the plant could possibly render measurement of the remaining leaves unnecessary. Among the characters used in predicting yield, plant height remained constant for a period shortly after flowering to maturity and ear size measurements, at time of maximum size, remained near the same magnitude for at least a week. The number of ears could be determined at the time the ears had reached their maximum size. Regression equations based on the 1940 data from Ames, Iowa; Lincoln, Nebr.; Urbana, Ill.; and Wooster, Ohio, were tested on data obtained in the following trials to determine the agreement between the actual and predicted yields: The 1938 and 1939 yields at Ames, the 1940 yields at Clarinda, and the 1941 yields from seven single cross tests in central and northern Iowa (Tables 7 and 8). Regression equations computed from the experimental tests of single crosses in 1941 were used in the prediction of the 1940 yields at the four experiment stations (Table 10). The general approach of using regression equations computed from various plant measurements appears to offer some promise as a method of forecasting yields of corn.