Maturity measurements in corn and an indication that grain development continues after premature cutting

Percentages of dry matter in the grain and kernel weights were measured at 4-day intervals in several corn hybrids during the latter part of their development periods in 1939, 1940, and 1941. The appearances of the ears and ear husks were noted at the time of the later harvests. In order to determine whether the kernels continued to increase after being cut and shocked, 26 bundles were cut prematurely and the kernel weights were measured before and after drying in the shocks for 8 days. Partially cut fields of corn were sampled in 1940 and 1941 to determine the stages of development at which corn is generally cut and shocked in Ohio. The following conclusions are based on the data presented: 1. Corn is not mature until it has reached the maximum dry weight of grain which occurs at about 65% dry matter. Within individual ears maturity is reached at a slightly earlier point. 2. Percentage of dry matter in the grain is the best single criterion of relative and actual maturities in corn within the dry matter range covered by this investigation (30 to 80%). The number of days to mid-silking is the second best criterion, although it was found to be misleading in specific comparisons. A combination of these two criteria, with greater emphasis on the dry matter in the grain probably is most desirable for corn investigators. 3. The time at which the maximum weight per 100 kernels has been reached is not a practicable measure of relative maturity among strains since it involves a series of measurements, and also the endpoint in kernel development is difficult to establish from the curves. 4. Ear appearance is the best practical guide for farmers to cut and shock corn unless moisture testing equipment is readily available. Maximum grain yields are attained when one-third to one-half of the ears are in the ripe stage and the remainder are in the hard dough stage. 5. Plant appearance is not a reliable index of relative or actual maturity. 6. Appreciable development of grain apparently occurs after immature plants are cut and shocked. Additional research is needed to verify this conclusion. 7. Harvesting is started before maximum possible yields of grain are attained in more than 50% of the fields that are cut and shocked in the areas surveyed. Harvesting may profitably be delayed for at least a week in many Ohio fields.