Simulated Hail Damage in Cotton in Arizona.

Accurate estimations of crop yield loss due to hail damage are important for taking management actions and adjusting hail insurance claims.  Current data on the yield loss estimation was developed from field experiments in southern states and is not applicable to southwestern states such as Arizona and California with much longer growing seasons. We estimated cotton yield loss by different levels of fruiting branch removal at different growth stages in Arizona. After each removal, the cotton canopy was scanned at different times using a reflectance sensor to measure plant growth after removal.  Seed cotton weight from different plant parts was also measured by plant mapping.  Cotton plants responded to fruiting branch removals by increasing growth and boll setting in other parts of the plant.  Yield reduction was related to percentage of fruiting branch removal but not to growth stage at which removal occurred.  If the main growth point is undamaged during hail storm during 8 to 16 fruiting branch stage, growers could recover 80% to 100% of their cotton yield under growing conditions in Arizona.  However, management practices might need to be adjusted after hail damage to increase cotton boll setting on top branches. There are potential benefits in implementing sensor technology in the form of canopy reflectance radiometers to make accurate assessment of the damage induced by hail. Moreover, these sensors can provide valuable information on the rate of recovery from such events.