File editing

Exercise objective:

·   Output data control (PRDEL and PRSEL).

·   Editing of data files continued (experimental data file); effect of crop establishment on growth and yield.

Suggested reading:

Chapters 7.1 and 7.2 of the book, ORYZA2000: modelling lowland rice.

In this exercise, we will practice more with the editing of data files, especially the experimental data file and the control file. In the control file, we will learn to control the format of the output produced by ORYZA2000. In the experimental data file, the exercises focus on the establishment practices of crop management (transplanting versus direct seeding, and plant density parameters).

Firstly, some options are given for formatting and selecting variables for the output data file RES.DAT.

Exercise:

Ex-1.18. In CONTROL.DAT, change the name of the experimental data file FILEIT from EXPERIMENT.DAT back to EXPLORE.DAT (verify in EXPLORE.DAT that STTIME = 4. and EMD = 4). Note the parameter PRDEL in CONTROL.DAT and its value 1. Run ORYZA2000 and have a brief look at RES.DAT (the Run_0 file) and make a simple graph (e.g. LAI vs. TIME). Now change the value of PRDEL from 1. to 10., run ORYZA2000, study RES.DAT again and make the same graph.

PRDEL defines the interval at which output variables are written in the file RES.DAT and in the file used for graphical output. With a value of 10., output is only written every 10 days. This option is convenient to limit the length of the files, to allow a quick overview of the results.

Ex-I.19. Reset the value for PRDEL from 10. to 1. Scroll down and remove the * in front of the line: PRSEL = 'TIME', 'DVS', 'WAGT', 'WSO', 'LAI'. Run ORYZA2000, study the file RES.DAT and make some graphs.

PRSEL (PRint SELect) allows you to include only a small selection of the output variables produced by ORYZA2000 in the output file RES.DAT. This is a convenient option for a quick scan of a small number of key variables you are interested in. Note that still all variables are available for plotting in the graphics mode.

Ex-I.20. Change some of the selected variables in PRSEL to others of your own choice, run ORYZA2000, and study the file RES.DAT. After you have finished, reset the * in front of the PRSEL line.

We will now exercise some more with file editing by changing crop management parameters in the experimental data file EXPLORE.DAT. This will also give particular insight into the effects of crop establishment on rice growth as simulated with ORYZA2000. In Table I.2, we have summarized in the column Sim1 some key variables simulated by ORYZA2000 in the ‘standard’ run using “RUNMODE=EXPLORATION”.

Ex-I.21. Run ORYZA2000, and use OP.DAT to verify the values in column Sim1 of Table I.2. If the values are not identical, check that STTIME and EMD are 4. Next, change the value of the seedbed duration (SBDUR) to 28 days, run ORYZA2000 and fill out column Sim2. Explain the differences with Sim1 (why is the yield higher?). A: The total crop duration (DAE) is longer, which means more sun light is (cumulatively) intercepted, which means that there is more photosynthesis, which means there is more biomass production.

Ex-I.22. Reset the duration in seedbed to 12 days, and change the number of plants per hill (NPLH) from 5 to 1. Run ORYZA2000 and fill out column Sim3 of Table I.2. Explain the differences with Sim1 (why is the yield lower?). A: The crop stand is less dense, which means less sun light is intercepted, which means less photosynthesis and less biomass accumulation.

Ex-I.23. Reset the number of plants per hill to 5, and change the number of hills per square meter (NH) from 25 to 10. Run ORYZA2000, and fill out column Sim4 of Table I.2. Explain the differences with Sim1 (why is the yield lower?). A: The crop stand is less dense (same as Ex I.22).

Ex-I.24. Reset the number of hills per square meter to 25, and change the number of plants direct-seeded in the main field (NPLDS) from 200 to 100. Run ORYZA2000, and fill out column Sim5 of Table I.2. Explain the differences with Sim1 (why is the yield the same?). A: No effect since we are still simulating transplanted rice!

Ex-I.25. Reset the number of plants direct-seeded in the main field to 200, and change the establishment mode ESTAB from transplanted to direct-seeded (ESTAB='DIRECT-SEED'). Run ORYZA2000, and fill out column Sim6 of Table I.2. Explain the differences with Sim1 (yield quite the same!).

Ex-I.26. Change the number of plants direct-seeded in the main field (NPLDS) from 200 to 100. Run ORYZA2000, and fill out column Sim7 of Table I.2. Explain the differences with Sim6 (why is the yield a bit lower?). A: The crop stand is less dense (same as Ex I.22).

Ex-I.27. Reset the number of plants direct-seeded in the main field to 200, and change the number of plants per hill (NPLH) from 5 to 1. Run ORYZA2000, and fill out column Sim8 of Table I.2. Explain the differences with Sim6 (why is the yield the same?). A: No effect since we are still simulating direct-seeded rice!

Ex-I.28. Reset the number of plants per hill (NPLH) to 5, and the establishment mode to transplanting. Verify that the simulation results are the same again as in column Sim1.

Table I.2.

View ANSWERS from the Tutorial_answer_sheet.pdf file.

These examples have highlighted the effect of crop establishment method (transplanting and direct seeding) on crop growth and development. They also showed that when the crop is transplanted, the parameters that are relevant for direct seeding (plant density in the main field) have no effect, whereas when the crop is direct-seeded, the parameters that are relevant for transplanting (plant density in the seedbed, number of plants per hill, and number of hills per square meter) have no effect.