Percent probability of blooms receiving 750 DD60s by the defoliation dates of September 20, October 1, and October 10 in the last 10 years
The following graphs show the percent of years that cotton blooms would receive 750 heat units by three defoliation dates. Heat units are DD60s (Maximum Daily Temperature + Minimum daily Temperature divided by 2 or the average daily temperature. The remainder of the average daily temperature minus 60 is the number of DD60s or heat units for a given day). The approximate number of accumulated DD60s for a cotton boll to reach full maturity is 750. At each location (Tunica, Stoneville, Onward ) historical weather data was used to calculate daily DD60s. Missing data was used from the nearest weather station. Each year the DD60s were accumulated back in time from each defoliation date to the date in August that 750 was reached. This date was considered the bloom date for the last mature boll to be harvested. Then, for each date in August, the number of years that 750 DD60s were accumulated from each defoliation date by that date or before, was divided by 10 and multiplied by 100 to give the percent probability that the bloom on that date would receive 750 heat units.