The cotton simulation model, OZCOT, is an important component of a number of current and future projects. It is a key tool both for exploring cotton crop responses and as a means of extending the outcomes of science into the industry. In this project we aimed to ensure the ongoing maintenance of the model as well as the continued incorporation of new science to improve our capacity to deal with current industry issues.

The project covered three main research components: 1.) exploring varietal differences in determinacy, 2.) exploring the model’s capacity to simulate compensatory growth responses to insect damage, and 3.) implementing a new soil water balance in the model. These areas were identified as being of current high importance by a meeting of researchers associated with the project, including Drs Greg Constable, Lewis Wilson, Mike Bange and Brian Hearn. Ensuring the model’s capability to simulate compensation is important for specific applications but the issues of growth form and soil water extraction are important for the general performance of the model and hence its application to a range of issues.

A complete review and restructure of the model has been undertaken. In addition to meeting existing usage requirements, the restructure has allowed considerable advances to be made towards making the science included in the model readily available to a much wider audience through conforming the model components to CSIRO Plant Industry’s Common Modelling Protocol.

Modifications have been made to the model to allow it to respond to pest damage. Research is underway to refine these modifications with the aim of developing a version of OZCOT that can be linked with EntomoLOGIC to improve pest management decisions and reduce insecticide use.

Coding for the use of the Montieth-Passioura approach in the Ozcot model has been completed is a version of the model using this approach has been developed. Collection of data for validation and for the development of a database of parameters for different soil types has been impared by drought and the reduced plantings of dryland crops.

This is the first study of which we are aware to attempt to derive an objective, quantifiable measure associated with determinacy in cotton. Two indices were developed which were well correlated to the breeders’ field assessment of determinacy, suggesting that they might provide a suitable basis for an index of determinacy. The measure based on rate of decline in nodes above last flower is the simpler of the two for field use.