Modelling Cotton Growth Dynamics, Yield, and Water Use Efficiency in Xinjiang Agricultural Systems

ABSTRACT Cotton ( Gossypium hirsutum L.) yield ( Y ) generally depends on the plant height ( H ), leaf area index (LAI), dry matter accumulation ( D ), and water consumption ( W ) of the entire growing period. Growing degree days (GDD) is an important meteorological factor affecting these growth indicators. This paper establishes a relative logistic growth model of H , LAI and D based on relative growing degree days ( R GDD ) and analyses the spatial variability characteristics of the model parameters. The influence degree of model parameters on Y , W and harvest index (HI) are determined using the grey relational analysis. A series of cotton mathematical models are then proposed based on maximum LAI (LAI max ) and W . The results reveal that the growth rates of cotton H , LAI and D were maximised when the R GDD is 0.43, 0.56 and 0.67, respectively. The coefficient of variation of the model parameter ranges from 0.1 to 1.0, indicating medium variability. The cotton HI and Y reach maximum values of 0.343 and 7236.464 kg/ha for LAI max values of 5.046 and 5.949 cm 2 /cm 2 , respectively. The corresponding required water consumption ( W ) is determined as 489.606 mm and 497.978 mm, while the water use efficiency (WUE) is 14.686 kg/(ha·mm) and 14.532 kg/(ha·mm), respectively. Furthermore, the cotton LAI max and W range from 2.719 to 7.225 cm 2 /cm 2 and 455.957 to 642.688 mm, respectively. This study provides a scientific foundation for enhancing Y and WUE in the agricultural regions of Xinjiang. Furthermore, the proposed methods enable the prediction of Y and WUE with improved accuracy.