On the Phenology of Field Corn, Silking to Maturity 1

R. H. SHAW AND H. C. S. TaoM SOFT corn results when field corn is killed by freezing before reaching maturity. Freezing temperatures kill the foliage of the immature plant and stop further development of the kernels. The two properties of soft corn of most interest from an economic standpoint are its reduced dry matter content and its high moisture percentage. The first property results in lowered test weight or feeding value and lowered value yield. The second creates a storage problem if the corn is picked too early and/or if weather conditions following freezing are unfavorable for drying. The seriousness of the soft corn problem in Iowa is sometimes underestimated. Since 1921 there have been 8 years in which more than 10% of the corn crop in Iowa was damaged by frost (13). During the period 1921-1945 the average amount of the corn crop damaged by frost was 12%. In 1924, 67% was damaged by an early freeze. The large loss in test weight in 1945, resulting from late corn not having reached maturity before a killing freeze occurred, brought renewed interest to the problem. In that year the average test weight of the Iowa corn crop was 5.6 pounds below the 10-year mean (1938-1947). In bushels this meant a loss of over 40 million bushels of corn in Iowa. It is apparent that both national agricultural planning and the individual farmer's planning demand early estimates of the contingence of soft corn, and prompt