Simulation of individual leaf areas in grain sorghum

Most crop simulation models that incorporate environmental conditions estimate leaf area development. The grain sorghum growth simulation model, SORKAM, calculates individual leaf area based on leaf number and maturity class. The objective of this study was to generalize present leaf growth routines in SORKAM to be independent of maturity since there are no generally accepted maturing classes. Modified relationships between leaf number and leaf growth parameters were developed from existing studies and were tested against independent detailed leaf growth data sets. The revised relationships improved the r 2 between simulated and actual individual leaf areas from 0.80 to 0.88, reduced the bias from 32 cm2 to 9 cm 2 , and the RMSE from 80 cm 2 to 52 cm 2 . With the improved simulation, estimated leaf area index through the season was also improved from the original SORKAM estimate (RMSE decreased from 0.77 to 0.63; RMSE: root mean square error). Although simulation of individual leaf areas was improved, total leaf area produced over the season was not.