Embedded Files
Exercise objective:
· Navigation continued; simple editing of input data files
· More contents of the experimental data file: EXPERIMENT mode
Suggested reading:
Chapter 7.2 of the book, ORYZA2000: modelling lowland rice.
In this exercise, we will learn to make changes in the input data files, and we will explore the experimental file a bit deeper. In the first set of exercises, we will study the differences between the start time of the simulation (STTIME) and the emergence time of the crop (EMD), and the differences between running ORYZA2000 in the exploration mode and in the experimental mode.
Exercise:
Ex-1.12. Open the file EXPLORE.DAT and search for the parameter EMD: day of emergence. Note that its value (4) is the same as that of the start time of the simulation (STTIME). Change the value of EMD to 150 (May 30). Run ORYZA2000 by clicking the green 4 button in the top bar of the screen. Use the information from output data files OP.DAT and RES.DAT to fill out column Sim2 in Table I.1 and compare with column Sim1.
Q: What is the difference and why?
A: Although we changed the emergence date, the simulation results are still the same. This is because in the mode RUNMODE = 'EXPLORATION', EMD is ignored as its value is overwritten by that of STTIME which was left unchanged.
Ex-I.13. In EXPLORE.DAT, reset the value for EMD to 4, and change the value of STTIME to 150. Don’t forget to put the dot (.) following the numerical value (i.e., 150.). Run ORYZA2000 by clicking the green 4 button in the top bar of the screen. Fill out column Sim3 in Table I.1 and compare with column Sim1.
Q: What is the difference and why?
A: Now the model starts simulation and crop emergence on day 150 and the crop grows under completely different weather conditions. The yield is lower, because with STTIME=150. the crop is grown in the wet season with less sunshine than when it is grown in the dry season (STTIME=4.) (see also the exercises of “Chapter II: Potential production”).
Ex-I.14. In EXPLORE.DAT, reset the value for STTIME to 4. Now go to the top of the file and change the run mode into RUNMODE = 'EXPERIMENT' by removing the * in front of this line and inserting it in front of the line: * RUNMODE = 'EXPLORATION'. In the experiment mode, ORYZA2000 is used to simulate a specific experiment and the value of EMD is not overwritten by that of STTIME. Everything else remains the same. Run ORYZA2000 and study the files OP.DAT and RES.DAT to verify that the output is the same as listed in column Sim1 of Table I.1 (both runs were executed with STTIME = 4. and EMD = 4).
Ex-I.15. In EXPLORE.DAT, set the value for EMD to 150, and run the model ORYZA2000. Fill out column Sim4 in Table I.1 and compare with Sim3. In RES.DAT, we notice that the model starts at TIME 4 (STTIME), but that no values for the crop variables are given until TIME 150, when the crop finally emerges (EMD). The results of the simulation are the same as that in Sim3 in the exploration run mode with STTIME = 150, except for the variable RAINCU. In RAINCU, the amount of accumulated rainfall is given since the start of simulation, and not since the start of emergence. After studying the output, reset the value for EMD to 4.
Now that we know the difference between running ORYZA2000 in the exploration or the experiment mode, we will study the experiment mode a bit further. For that purpose, we will use a new experimental data file called EXPERIMENT.DAT. The simulation environment and crop management are exactly the same as in EXPLORE.DAT. The only difference is that EXPERIMENT.DAT contains observed and measured crop data from an actual field experiment with cultivar IR72 that was conducted at IRRI in the dry season of 1992. In this experiment, one of the treatments was aimed at realizing potential yield by applying a very high dose of nitrogen fertilizer (225 kg N ha-1). At selected times during the experiment, crop cuts were taken to determine the leaf area index and the weights of different crop organs (stems, leaves and panicles). These measured values were included in the experimental data file for comparison with simulated values.
Ex-I.16. Open the CONTROL.DAT file and change the name of the experimental data file FILEIT from EXPLORE.DAT into EXPERIMENT.DAT. Open the file EXPERIMENT.DAT and study its contents. Verify that the simulation conditions are the same as in EXPLORE.DAT. Go to the bottom of the file and study Section 8 ‘Measured data’; compare with the same section in EXPLORE.DAT.
There are two types of observations on the crop in Section 8. The first are observed values of phenological development. The second are measured leaf area index and weights of crop organs as function of time: year and day of observation. The conversion of calendar dates (month and day of month) into daynumber (number of days counted since January 1) is given in Appendix 8.
Ex-I.17. Run ORYZA2000. Open OP.DAT and verify that the simulation results are the same as in column Sim1 in Table I.1. Open the graphics window by clicking on CHART.TXT. Make a graph with TIME on the X-axis, and simulated total weight (WAGT) and observed total weight (WAGT_OBS) of the above-ground crop on the Y-axis. Study the goodness-of-fit of the simulation. Go back to the selection of variables and add the simulated and observed weight of panicles (WSO and WSO_OBS) to the graph. Then remove WSO and WSO_OBS and add the simulated and observed weight of green leaves (WLVG and WLVG_OBS) or the simulated and observed weight of stems (WST and WST_OBS). Finally, plot the simulated and observed leaf area index (LAI, LAI_OBS) versus the development stage (DVS).
Figure I.2. Simulated and observed leaf area index (-) as function of development stage (DVS).
NOTE: Only the observed leaf area index and weights of crop organs can be plotted. The observations on phenology are not read by ORYZA2000, but can be used by the program DRATES for calibration of ORYZA2000 (see Chapter 8.2 of the book “ORYZA2000: modelling lowland rice” and the exercises in “Chapter VI: Model parameterization”).
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