Appendix VII

The use of the crop data in CGMS

Introduction

The data describing the crops falls broadly into two categories. The first category of data contains the data that describes the various crops for the WOFOST model. These so-called crop parameters describe characteristics of the crop like for example the threshold temperature sum from emergence to anthesis, or the leaf area index at emergence. The second category of data, the crop-calendar, describes the spatial and temporal variation in the use of the crop, for instance which crop is used in a particular location and what the sowing and harvest dates are for this crop. Within these categories, the crops are defined either by a crop number or by the crop group number. The association between these numbers and the crop name is described in the table CROP, which for a typical installation could look like follows:
 

 

CROP_NO CROP_NAME CROPGROUP_NO
1 wheat 1
2 grain maize 1
3 barley 1
5 rice 1
6 sugar beet 2
7 potato 2
8 field bean 1
9 soy bean 1
10 rape seed 1
11 sun flower 1

 

 

Crop parameters

The crop parameters are contained in three tables, CROP_PARAMETER_VALUE, VARIETY_PARAMETER_VALUE and PARAMETER_DESCRIPTION. The crop parameter table contains values for all parameters as described in the parameter description table. These parameters are the values used by WOFOST, to simulate crop behaviour. To introduce other parameters there are two possibilities. When a crop is basically the same as an existing crop (in terms of the WOFOST crop parameters) it is convenient to express the differences by introducing only those parameters that are different in the variety parameter table. If however the crop is significantly different, it is more convenient (and more logical) to introduce a completely new crop in the crop parameter table. It is important to realise that for the system this is no different, since theoretically all of the crop parameter values can be overwritten by a variety parameter value.

The parameters fall into two categories. One category contains the parameters that can be expressed as a single number, e.g. TSUM1, the temperature sum from emergence to anthesis. The other category contains the parameters that can be expressed as a function of another variable, e.g. SLATB, the specific leaf area as a function of DVS. These parameters are expressed as a set of value pairs (x,y) that describe the shape of the function. An AFGEN function is used to obtain the function values for arbitrary inputs. Format of the parameter description table is:

PARAMETER_CODE name of the parameter (note that these names are fixed by the system and can not be changed)
MULTIPLE Y == single value, N == value pairs
PARAMETER_DESCR a textual description of the parameter

Naming convention for multiple parameters is parameter name, postfixed by _XX. XX ranges from 01 to 10 or 15, depending on the parameter (see the parameter description table). At the moment of writing these limits are fixed.
 

Crop calendar

The crop calendar table describes the temporal and spatial distribution of crops and is linked to the grid system. When for a specific grid a crop is to be simulated, the crop calendar contains the information about crop variety to be simulated, and information about sowing and harvesting days and simulation strategies. The CROP_CALENDAR table has the following fields:
 

GRID_NO grid number
CROP_NO the crop number (see also table crop)
VARIETY_NO variety 1 is the main crop
START_TYPE defines the start of simulation strategy
START_MONTHDAY1 depends on start type
START_MONTHDAY2 depends on start type
START_MONTH1 depends on start type
START_MONTH2 depends on start type
END_TYPE defines the end of simulation strategy
END_MONTHDAY depends on end type
END_MONTH depends on end type
MAX_DURATION maximum number of days for simulation

 

Start of the crop growth simulation is defined by the start type, which can take the following values:
 

VARIABLE_SOWING: The sowing date is determined by the program. The program starts evaluating sowing conditions 10 days before the earliest sowing date (given by START_MONTH1 and START_MONTHDAY1 ) and will return the earliest sowing date within the period between the earliest and the latest sowing date (defined by START_MONTH2 and START_MONTHDAY2 ). Emergence is calculated using the effective daily temperature (defined by the crop parameters TBASEM , TEFFMX and TSUMEM ).
FIXED_SOWING: Sowing date is given by START_MONTH1 and START_MONTHDAY1 . Emergence is calculated using the effective daily temperature (defined by the crop parameters TBASEM , TEFFMX and TSUMEM ).
FIXED_EMERGENCE: Emergence takes place on the day given by START_MONTH1 and START_MONTHDAY1 .

End of the crop growth simulation is determined by the end type, which can take the following values:
 

HARVEST: Simulation stops at the date given by END_MONTHDAY and END_MONTH. If maturity is reached before this date, the model stops at maturity. This option is useful for crops that are harvested in the vegetative state, e.g. sugar beet. MAX_DURATION is not used)
MATURITY: Simulation stops at maturity, but the simulation will not exceed MAX_DURATION days after emergence. The use of MAX_DURATION will prevent anomalies when a crop never reaches maturity due to low temperatures. ( END_MONTHDAY and END_MONTH are not used)
EARLIEST: Simulation stops at the earliest of maturity, end date or maximum duration.

 

 

Crop Yield

The final CGMS results are stored in table CROP_YIELD_X. The X stands for the crop number, e.g. the results for wheat are stored in CROP_YIELD_1.Name of this table is slightly misleading since many results are stored here, not just the crop yield. Results are stored as function of the simulation period (called ‘decade’), year and EMU . The EMU is expressed as the combination of GRID_NO, NUTS_CODE and SMU_NO . The results are stored for each simulation period requested by the user. Note that the simulation itself is always carried out from the beginning of the growing season. The crop yield tables contain the following fields:
 

DECADE the simulation period (roughly 10 days)
YEAR the year
SMU_NO SMU for the EMU
NUTS_CODE NUTS code for the EMU
GRID_NO GRID number for the EMU
POTENTIAL_YIELD_BIOMASS potential total biomass (kg/ha)
POTENTIAL_YIELD_STORAGE potential dry weight storage organs (kg/ha)
WATER_LIM_YIELD_BIOMASS idem for water limited
WATER_LIM_YIELD_STORAGE idem for water limited
POTENTIAL_LEAF_AREA_INDEX potential leaf area index
WATER_LIM_LEAF_AREA_INDEX water limited leaf area index
DEVELOPMENT_STAGE development stage (0-200)
RELATIVE_SOIL_MOISTURE percentage of (field capacity – wilting point)
TOTAL_WATER_CONSUMPTION sum of water limited transpiration
TOTAL_WATER_REQUIREMENT sum of potential transpiration

 

 

PARAMETER DESCRIPTION

Name Multiple Description
AMAXTB_01 Y max. leaf CO2 assim. rate as a function of DVS [kg ha-1 hr-1/-]
AMAXTB_10 Y idem
CFET N correction factor transpiration rate [-]
CVL N efficiency of conversion into leaves [kg kg-1]
CVO N efficiency of conversion into storage org. [kg kg-1]
CVR N efficiency of conversion into roots [kg kg-1]
CVS N efficiency of conversion into stems [kg kg-1]
DEPNR N crop group number for soil water depletion [-]
DLC N critical daylength (lower threshold) [hr]
DLO N optimum daylength for development [hr]
DTSMTB_01 Y daily increase in temp. sum as a function of av. temp. [°C/ ° C]
DTSMTB_10 Y idem
DVSEND N development stage at harvest (=2.0 at maturity) [-]
EFF N light use effic. single leaf [kg ha-1 hr-1 J-1 m2 s]
FLTB_01 Y fraction of above-gr. dry matter to leaves as a function of DVS [kg kg-1/-]
FLTB_15 Y idem
FOTB_01 Y fraction of above-gr. dry matter to stor. org. as a function of DVS [kg kg-1/-]
FOTB_15 Y idem
FRTB_01 Y fraction of tot. dry matter to roots as a function of DVS [kg kg-1/-]
FRTB_12 Y idem
FSTB_01 Y fraction of above-gr. dry matter to stems as a function of DVS [kg kg-1/-]
FSTB_15 Y idem
IAIRDU N air ducts in roots present (=1) or not (=0)
IDSL N indicates whether pre-anthesis development dep. on temp.(0), dayl.(1), or both(2)
KDIF N extinction coefficient for diffuse visible light [-]
LAIEM N leaf area index at emergence [ha ha-1]
PERDL N max. rel. death rate of leaves due to water stress
Q10 N rel. incr. in resp. rate 10 Cel temp. incr. [-]
RDI N initial rooting depth [cm]
RDMCR N maximum rooting depth [cm]
RDRRTB_01 Y relative death rate of stems as a function of DVS [kg kg-1 d-1/-]
RDRRTB_10 Y idem
RDRSTB_01 Y relative death rate of roots as a function of DVS [kg kg-1 d-1/-]
RDRSTB_10 Y idem
RFSETB_01 Y reduction factor for senescencs as a function of DVS [-/-]
RFSETB_10 Y idem
RGRLAI N maximum relative increase in LAI [ha ha-1 d-1]
RML N rel. maint. resp. rate leaves [kg CH2O kg-1 d-1]
RMO N rel. maint. resp. rate stor. org. [kg CH2O kg-1 d-1]
RMR N rel. maint. resp. rate roots [kg CH2O kg-1 d-1]
RMS N rel. maint. resp. rate stems [kg CH2O kg-1 d-1]
RRI N maximum daily increase in rooting depth [cm d-1]
SLATB_01 Y specific leaf area as a function of DVS [ha ha-1/-]
SLATB_10 Y idem
SPA N specific pod area [ha kg-1]
SPAN N life span of leaves growing at 35 Celsius [d]
SSA N specific stem area [ha kg-1]
TBASE N lower threshold temp. for ageing of leaves [°C]
TBASEM N lower threshold temp. for emergence [°C]
TDWI N initial total crop dry weight [kg ha-1]
TEFFMX N max. effective temp for emergence [°C]
TMNFTB_01 Y reduction factor of gross assim. rate as a function of low min. temp. [°C]
TMNFTB_10 Y idem
TMPFTB_01 Y reduction factor for AMAX as a function of av. temp. [° C]
TMPFTB_10 Y idem
TSUM1 N temp. sum from emergence to anthesis [° C]
TSUM2 N temp. sum from anthesis to maturity [° C]
TSUMEM N temp. sum from sowing to emerge. [°C]

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