Testing the performance of ORYZA1, an explanatory model for rice growth simulation, for Mediterranean conditions.

摘要

ORYZA1 was calibrated and validated with field data for a short-grain (cv. Tebre) and a long-grain rice cultivar (L-202) grown in 1994-96 in the Ebro Delta of Spain. Phenological development, daily dry matter production and leaf area development were calibrated. There were no significant differences between the cultivars for the total length of the growth period. However, the pre-heading period was longer and the post-heading period shorter in L-202 than in Tebre. This resulted in differences in translocation characteristics, spikelet number per unit area, weight of the grains and harvest index. The following crop characteristics were similar in the 2 cultivars: extinction coefficient, dynamics of nitrogen distribution, partitioning of assimilates, relative death rate of leaves, relative growth rate of leaf area during exponential growth, specific leaf area and specific stem green area. The simulated curve fitted the observations much better when leaf area index was considered as comprising the leaf blade area only, without a photosynthetic contribution by the stem green area. The model simulated rice growth very accurately until flowering. After flowering, however, divergences appeared and increased especially at the yellow ripe stage. From then on the crop did not grow much more, whereas it continued in the simulation. This reduction of growth rate was usually accompanied by an increase in the relative death rate of leaves and the drying of the grains. The main source of error may be a limited understanding of the ripening and sink limitation processes. A considerable yield gap between potential and observed yield remained. A climatic variability assessment over 10 years, from 1987 to 1996, showed a small but correlated variation in both simulated and measured rice yields.