A Trend Toward a Longer Grain‐Filling Period for Corn: A Case Study in Indiana1

Abstract

AbstractIn assessing the effect of weather on crop growth and yield it is necessary to consider the stage of crop development. In most states since 1951 the USDA Statistical Reporting Service (SRS) has collected and summarized reports of crop progress during each season. For corn (Zea mays L.) and crop reporting districts (CRD) in Indiana, dates by which 50% of the corn acreage had been planted, silked, and matured were used to examine the trends in length of the corn vegetative and grain‐filling periods, measured in both days and thermal units from 1951 to 1980. It was found that there has been little change in the length of the period from planting to silking, but that the period from silking to maturity has increased from less than 50 days before 1961 to near 60 days in 1980. Although a climatic cooling trend may have contributed to this longer period of grain filling, the modified (10 to 30°C cutoff base) growing degree days required during the corn grain−filling period (silking to maturity) also increased, from less than 550 before 1961 to near 700 in 1980.