Building Of Greenhouse Cucumber Dry Matter Accumulation Model And Its Comparison With Mechanistic Model

Most of cucumber dry matter production model is explanatory models, which provide more thorough insight into the mechanisms but have large numbers of parameters. The objectives of this paper were to develop a empirical cucumber dry matter production model with a minimum number of parameters and compared it with the existing popular mechanistic cucumber dry matter production model. Cucumber were cultivated in Beijing Academy of Agriculture Forestry Sciences, Chinese Academy of Agricultural Science and China Agricultural University in 2004. Cucumber growth dada were collected every 10 days. Entironment data were collected every 10 minutes.1. A empirical model for cucumber dry matter production was developed. Based on Logistic curve, the time state variable in Logistic function was expressed as a function about effective accumulated temperatures (GDD) and effective accumulated light intensity (RDD, the sum of product in certain period was defined as the new concept and the product was that light intensity higher than light compensation point multiplied with time) in this model. The model have less state variable and describe the relationships between the cucumber dry matter accumulation per plant (Dr) and temperature, radiation and day length. Data from experiment Data from other 4 experiments in solar greenhouse were used to validate the model. The results showed that the R2 value was 0.99 and the value of RMSE was less than 6.2. Estimating three important parameters of a popular cucumber dry matter production mechanistic model at present and validating the model. The value of maximum photosynthesis when CO₂ concentration was 340 μ mol · mol^-1 (P_mc) is 21.4 μ molm^-2s^-1; the value of light use efficiency( Qe) is 0.045; the value of the efficiency of conversion of assimilates into structural dry weight(Cf) is 0.7. Simulated dry matter production agrees well with the measured in Exp.3 and under-estimate about 7-37% in Exp.2. The validation results showed that the R² value was 0.99 and the value of RMSE was less than 15.3. the model of single leaf area and leaf area index for cucumber were gained.4. The empirical model and mechanistic model of cucumber dry matter production was compared. The result showed that the empirical model is more accurate than mechanistic model and have small number of parameters. The empirical model have apparently advantage in greenhouse production system.