Modeling phenological development in Cotton

Accurate prediction of crop phenology is important in crop simulation models. The objective of this work was to quantify the occurrence of phenological stages in cotton and to construct a simple phenology model. Required parameters of model were obtained from a serially sown field experiment (22 April, 5 May, 24 May, 13 June, 9 July, and 7 August in 2006). The results showed that none of developmental stages is sensitive to photoperiod (on based phonological stages reaction to GDD), so only temperature was taken into account. Also, there was no difference between hourly, 3-hourly and daily temperature data. Therefore, average daily temperature can be used in predicting developmental stages. For independent test of the model, data from different field experiments that were carried out at Hashem-Abad and Karkandeh stations were used. Root mean square errors (RMSE) between simulated and experimental data were 1.8 d for emergence, 7.2 d for squaring, 5.5 d for flowering, and 7.8 d for open boll. Therefore, this model can be used to predict development stages in cotton simulation model in non-stress conditions.