Introduction

This book documents the ecophysiological crop model ORYZA2000 to simulate the growth, development, and water balance of lowland rice. ORYZA2000 follows the principles of the “School of de Wit” crop growth simulation models (Bouman et al 1996). It simulates the growth and development of a rice crop in situations of potential production, water limitations, and nitrogen limitations (de Wit and Penning de Vries 1982):

In all production situations, the crop is supposed to be well protected against diseases, pests, and weeds and no reductions in yield occur.

 

ORYZA2000 is the successor to a series of rice growth models developed in the 1990s in the project “Simulation and Systems Analysis for Rice Production (SARP)” (ten Berge and Kropff 1995). It is an update and integration of the models ORYZA1 for potential production (Kropff et al 1994a), ORYZA_W for water-limited production (Wopereis et al 1996a), and ORYZA-N for nitrogen-limited production (Drenth et al 1994). Since the release of these models, new insights into crop growth and water-balance processes have been gained, new scientific subroutines developed, and programming standards and tools improved. These developments warranted a new release in the ORYZA series. Besides the scientific and programming updates, ORYZA2000 contains new features that allow a more explicit simulation of crop management options, such as irrigation and nitrogen fertilizer management.

 

Chapter 2 of this book describes the general structure of ORYZA2000 and the so-called FORTRAN Simulation Environment (FSE) in which it is programmed. Chapter 3 gives a complete description of the crop growth processes modeled. Chapter 4 describes how evapotranspiration is computed and how effects of water stress on crop growth and development are calculated. Chapter 5 describes the nitrogen balance in the crop and the calculation of nitrogen stress factors that affect crop growth and development. It also describes the subroutine that computes the availability and uptake of nitrogen from the soil. Chapter 6 documents the soil-water balance model PADDY. Chapter 7 explains the input data files needed to run ORYZA2000 and the generated output files.

 

Each parameter and its corresponding value in the input data files are explained in detail. The last chapter, Chapter 8, explains how to install ORYZA2000 from a CD-ROM, set up data files, and run the model. Two other programs designed to assist in model parameterization are explained here: DRATES and PARAM. Separate paragraphs describe the validity domain and practical applications of ORYZA2000. The list of variables at the end of the book describes all the variables used in ORYZA2000.

 

The CD-ROM in the back of this book contains the model ORYZA2000, its source code, and three sets of example data files. The only source code not made available is that of three libraries of nonscientific utility routines and functions (TTUTIL, WEATHER, and OP_OBS). Besides ORYZA2000, the programs DRATES and PARAM for model parameterization and the program TTSELECT for quick-viewing of simulation results are included. Chapter 8 details how to install these programs from the CD-ROM on a computer for further use.

 

ORYZA2000 uses several scientific subroutines and nonscientific libraries that have been documented elsewhere. Since these documents are mostly technical reports with limited copies, they have been included on the CD-ROM with permission from the authors. They are reports on the libraries TTUTIL (van Kraalingen and Rappoldt 2000) and WEATHER (van Kraalingen et al 1991), on the evapotranspiration models (van Kraalingen and Stol 1997), on the FORTRAN Simulation Environment (FSE; van Kraalingen 1995), and on the program TTSELECT (van Kraalingen, unpublished document). Though much care has been taken to make the software easy to use and free of errors, please remember that the software originated in an academic environment and was not designed for commercialization. Models are never finished and need continued updating as new insights develop. Also, researchers may have different opinions on how to (mathematically) model certain processes of crop growth. By providing the source code of ORYZA2000, we encourage users to experiment with the model and make changes or additions according to their own insights and model needs.

 

ORYZA2000 has a long history and many people have contributed directly or indirectly to its creation. Special thanks are due to D.W.G. van Kraalingen, who designed and programmed most of the overall modeling structure and the technical libraries, and programmed many of the scientific subroutines used by ORYZA2000. Part of this book is based on earlier descriptions of ORYZA models, by Drenth et al (1994), Kropff et al (1994a), and Wopereis et al (1996a).