Establishment of morphology simulation model for above-ground part of cotton plant

There are three reasons for the increasing demand of crop models that build plants on the basis of architectural principles and organogenetic processes. The first of these reasons is that realistic concepts of developing new crops need to be guided by such models. The second is that there is an increasing interest in crop phenotypic plasticity based on variable architecture and morphology. The third reason is that engineering of mechanized cropping systems requires information on crop architecture. Functional-structural plant models (FSPM) are the best bridge to connect the function and structure of plant growth and development, which are the tendency of future plant models. FSPM is a digital tool for crop growth regulation and variety design. With regard to studies on cotton cultivation in China, an explanatory model of cotton growth and development (COTGROW) was developed and modified based on the processes of the GOSSYM cotton model. The COTGROW model included meteorological, soil and other environmental conditions and management practices modules. The objective of this study was to construct a virtual growth model of cotton with eco-physiological processes. Field experiments with different densities of cotton cultivar "NuCoTN 33B" were conducted for 2008-2010 in Anyang (36°07?N, 114°22?E) of Henan Province, China. The experiment included five planting densities (plants·m^-2): 1.5, 3.3, 5.1, 6.9 and 8.7. Plants were sown on 18 April in 2008 (Exp. 2008), 26 April in 2009 (Exp. 2009) and 29 April (Exp. 2010). Each treatment had three replications in a randomized complete block design. Five plants were collected for each replication at the sampling dates. The soil was a sandy clay-loam, previously managed as meadow land. The plots were irrigated and fertilized to avoid nutrient and water limitations to plant growth. Weeds were removed by hand to avoid herbicide effects on the plant growth. No plant disease, pest or stress symptoms were observed. Detailed observations were made on the dimensions and biomass of above-ground plant organs for each phytomer throughout the seasons. Growth stage-specific target files (a description of plant part weight and dimension based on plant topological structure) were established from the measured data. The relationship between biomass and morphology of the above-ground cotton plant parts was analyzed and used to establish a cotton simulation model for above-ground parts. This algorithm improved the development and morphogenesis modules in COTGROW. A preliminary model calibration was carried out using the experimental data for 2008 and 2009, and the model was validated using independent experimental data for 2010. The results showed that the simulated values agreed well with the measured ones. Correlation coefficient (R) and root mean squared error (RMSE) between the measured and simulated values of morphological parameters were determined. The determined R for plant height, main stem node number, fruiting branch number, fruiting branch node number, internode length, internode diameter, leaf blade length, leaf blade width, petiole length, petiole diameter, boll length and boll diameter were 0.99, 0.99, 0.99, 0.92, 0.95, 0.93, 0.75, 0.71, 0.81, 0.62, 0.98 and 0.98, respectively. The corresponding determined RMSE for the above parameters were 3.85 cm, 0.64, 0.52, 0.66, 1.00 cm, 0.15 cm, 1.58 cm, 2.39 cm, 2.54 cm, 0.05 cm, 0.13 cm and 0.10 cm, respectively. The results indicated that the model achieved a good performance in simulating the growth processes of the above-ground parts of cotton plant. It was further possible to build a visual plant model from the above model.