[Modeling of cotton boll maturation period and cottonseed biomass accumulation]

Field experiments with different maturity cotton cultivars and sowing dates were conducted at different sites to quantitatively study the effects of cultivar characteristics, weather conditions (air temperature and solar radiation), and crop management variable (N application rate) on the cotton boll maturation period and cottonseed biomass accumulation. The cotton boll maturation period was simulated by using the scale of physiological development time. Based on the hypothesis of sink-determined, the cottonseed biomass accumulation model was then developed. The subtending leaf N concentration of cotton boll was simulated with a semi-empirical equation, and used as the direct indicator of the N nutrition effect on cottonseed growth and development. The model was tested by independent field data obtained in the Yellow River Valley (Xuzhou and Anyang) and the lower reaches of Yangtze River Valley (Huaian) in 2005. The simulated values of boll maturation period showed reasonable agreement with observed values, with a root mean square error (RMSE) of 2.25 days for cultivar DSC-1, of 2.61 days for cultivar KC-1, and of 2.75 days for cultivar AC-33B. The RMSE of cottonseed dry mass prediction was 9.5 mg x seed(-1) for KC-1 and 8.2 mg x seed(-1) for AC-33B, indicating that the model had a good prediction precision.