Simulation Model of Cottonseed Protein and Oil Formation

Abstract

The simulation of cotton (Gossypium hirsutum L.) seed growth is an area of great uncertainty, especially in the process of cottonseed quality formation. To simulate the formation of cottonseed protein and oil under different environmental conditions, we developed a simple process-based model driven by the inputs of cultivar parameters, weather information, and crop manage- ment variable (precisely N supply). A set of field experiments were conducted with Kemian 1 and NuCOTN 33B in the lower reaches of Yangtze River Valley (Nanjing, Huai’an) and the Yellow River Valley (Xuzhou, Anyang) in 2005. Two sowing dates and three N rates were set in the trials. According to the data collected in Nanjing, the response functions of cottonseed protein and oil accumulation to weather conditions (temperature, solar radiation), crop management (variable N supply) and boll positions were all developed and involved in the model. The subtending leaf N concentration of cotton boll obtained from a semi-empirical equation was made as a direct indicator of the N nutrition affecting cottonseed quality formation. The model was based on the hypothesis that nitrogen accumulation and oil synthesis in cottonseed are mainly sink-determined, and was integrated with the cotton boll maturation period model and cottonseed biomass accumulation model. The parameters in the model were calibrated using the field data obtained in Nanjing. The model was tested using the field data obtained in Huai’an, Xuzhou and Anyang. The root mean square error (RMSE) of the simulated and measured cottonseed protein contents was 2.05% for Kemian 1 and 2.33% for NuCOTN 33B. The RMSE of the simulated and measured cottonseed oil content was 2.45% for Kemian 1 and 2.95% for Nu-COTN 33B. Driven by the inputs of data including weather conditions (daily maximum, minimum and average temperatures and daily solar radiation), management variable (precisely N supply), the present model accurately predicted cottonseed protein content and oil content under diverse environmental conditions. This model is a necessary component of cotton growth model, and provides a good platform for further study on modeling cottonseed protein and oil yield.