Modeling Cotton Fruiting Form Abscission1

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Abstract
Abscission of cotton (Gossypium hirsutum L.) fruit and flower buds occurs even in well managed crops and influences subsequent fruit growth and development. Relationships that describe the abscission of flowering buds (squares), flowers, and fruit (bolls) were developed and incorporated into a process‐based cotton crop simulation model. These relationships are essential components of yield simulation models useful for management decision making. The abscission model developed is based on established hormonal and nutritional theories. Younger squares and bolls are predicted to abscise more readily than older ones. Abscission of bolls and squares depends on organ age, boll load, and environmental stresses. External stresses and internal competition for carbohydrates modify the probability of abscission multiplicatively. The effects of insects are approximated through a factor representing a uniform level of shedding throughout the growing season. Detailed fruiting site plant maps of greenhouse grown plants were used for model calibration. Simulations were carried out using input data collected at California, Texas, and Arizona. Simulated fruit development was in agreement with observed fruiting form counts and the frequency distribution for fruiting form age at abscission agreed with field observations.