cotton growth stages, Arizona
We are using a growing degree day (heat unit) model for estimating cotton growth stages worldwide and I am using NASS data (https://quickstats.nass.usda.gov/) to calibrate this model. I noticed that it takes much more time (and many more GDDs) between '50% Bolls Opening' and '50% Harvested' in Arizona than in other states such as Georgia, South Carolina, Louisiana, Tennessee, Kansas, California. What is different in Arizona compared to these other states? Thanks!
Arizona uses a different DD60 system due to higher diurnal fluctuations in temperatures in a desert environment http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1602.pdf
The one we and most of the other cotton growing sates use is in this book