8. Corn hybrids differ in harvestability.

In tests or harvestability with the mechanical picker, some hybrids were picked much cleaner and more nearly completely than others. Corn hybrids differed in

a. Time required to harvest

b. Ear droppage

c. Ears left on plants by harvester

d. Husks left on harvested ears

e. Shelled corn lost on ground.

In a series of comparable single crosses in 1947, 20 per cent of the ears of K180 crosses were left in the field by the mechanical harvester compared to only 5 per cent of the ears of C.I.7 and H7 crosses. Individual hybrids ranged from 0 to 31 per cent of the ears left in the field. On the average ears of K180 crosses had about 1 gram of husks compared to 6 grams of husks on ears of K148 crosses. Individual hybrids ranged from 0 to 10 grams of husks left on harvested ears. A correlation of +0.8 was obtained between percentage of ears left by the harvester and percentage of lodged plants at harvest. One hundred and fifty‑two double crosses ranged from 0 to 16 per cent of the ears left in the field by the mechanical harvester, and from 1 to 9 grams of husks left on harvested ears. These differences were statistically significant.

In 1948, 88 double crosses, and 45 single crosses, involving all possible combination of 10 inbred lines, were compared for differences in mechanical harvestability. Under conditions of little lodging, the differences in number of ears left in the field by the mechanical harvester usually were not significant. However, the double crosses ranged from 1 to 17 grams of husks left on each harvested ear and the single crosses from 0 to 18 grams. Differences of 3 grams or more were significant. U. S. 13 had an average of 1 gram of husk per harvested ear compared to 17 grams per ear for U. S. 537W. The inbred lines performed similarly to their average performance in single‑crosses.

Since more than 75 per cent, or nearly 7,000,000 acres, of the Illinois corn acreage is harvested with mechanical pickers, harvestability is an important characteristic.