Like last week’s report, the USDA-NASS Crops & Weather report for the week ending Sept 15th shows our corn crop continues to lag behind normal and last year in particular. According to the USDA-NASS report as of Sunday, Sept 15th, 15 % of Iowa’s corn was “Safe from frost.” That means the crop is physiologically mature (R6) and thus beyond the damaging effects of a killing frost: 28⁰ F or colder for several hours.(1
Table 1 summarizes the crop development data from the USDA-NASS report but in a different way than originally published showing the percentage of the crop in the different developmental stages.
One quarter to one-third of the corn in Central, South Central, and Southeast Iowa Crop Reporting Districts – CRD – was mature (R6) and thus safe from frost. Development is furtherest behind in the state’s 3 northern CRD’s (6-10% mature in those CRD’s).
As mentioned above, statewide, only 15% of the crop has reached R6 contrasting with the 5-year average of 45% and last year’s 86%. In one sense, having numbers this close to ‘normal’ is remarkable considering our late planting dates. Stressful conditions have accelerated crop development and in the process likely reduced yields.
Dry matter accumulations and kernel dry matter accumulation at different development stagers as well as historical frost probabilities are included in an ICM News posted on August 19th.
1) Obtain the publication Corn Growth and Development for complete descriptions of development stages.