Configuring and Parameterising FarmAC

1 Contents

Configuring and Parameterising FarmAC.. 1

1 Contents. 1

2 Introduction. 1

3 Configuration. 2

3.1 Agro-ecological zone. 2

3.2 Crops. 2

3.3 Soil type. 2

3.4 Livestock and manure management 2

4 Parameterisation. 3

4.1 Parameter files. 3

4.2 Editing XML files. 4

5 Appendix Details of parameter files. 6

5.1 Constants.xml 6

5.2 Feedstuff.xml 8

5.3 FerMan.xml 9

5.4 Parameters.xml 10

5.5 Sources. 18

5.5.1 Climate data. 18

5.5.2 Crop parameters. 23

2 Introduction

From within the FarmAC web-based interface, it is possible to describe a wide range of farms. This includes the agricultural land (areas, soil types, crops etc.), livestock (type of ruminants, their feed rations, their housing and associated manure storage) and fertilisation and manuring of crops. The choices available to the user to describe their farms depend on the Agro-ecological zone they select. The choices available are read from a database on the Internet server and for the foreseeable future, the only way to add, subtract or modify these choices is to contact the webmaster (Margit) by email.

3 Configuration

When requesting that a new choice of crop, livestock etc. be made available, it is often necessary to provide several items of information. The items of information that need to be provided are specified below.

3.1 Agro-ecological zone

The only information required is the name of the zone. However, all aspects of the farm (crops, soils, livestock etc.) are ordered individually for each AEZ, so if you define a new AEZ, you will need to parameterise all these components. Fortunately, it is not necessary to define a new AEZ very often and only needs to be done once.

3.2 Crops

For a new crop, it is necessary to supply:

· A name. If you wish the crop to be treated as established (e.g. permanent grass) then the name must contain the key text 'Permanent'.

· One or more primary crop products from which the user will choose just one. For grain crops, this would normally be grain. It is possible to provide more than one quality of grain (e.g. spring barley, high protein; spring barley low protein). Likewise for roughage crops (e.g. high quality grass silage, low quality grass silage).

· Whether the primary crop product can be grazed.

· One or more secondary crop product from which the user will choose just one. For grain crops, this would normally be straw. As for the primary product, it is possible to provide more than one quality.

· Whether the secondary crop product can be grazed, harvested, incorporated into the soil, burnt or whether the remaining stubble can be burnt.

Certain crops, principally associated with small-scale farms in developing countries, crop residues may be left on the field after harvesting and used in situ as roughage for ruminant livestock. These crop products must have a name that includes the key text 'residue'.

3.3 Soil type

Only the name is required.

3.4 Livestock and manure management

The main function of the livestock modelling is to estimate production, losses of C (CH₄ and CO₂) and excretion. The feed ration for each livestock group must be input by the user; the feed items available are specific to an AEZ and will include the crop products defined above. Since livestock will often be housed during all or part of the year, there is a need to connect livestock to housing, so that flows of C and N through the manure management system can be followed.

The information required concerning livestock and manure management is:

· The name of the livestock group.

· If the livestock can be housed, the list of housing types must be given.

· If livestock housing are given then for each housing type, a list of the manure storage facilities (e.g. slurry tank, dung heap) that can receive manure must be given.

4 Parameterisation

Parameters are associated with all farm components. The following parameter files are used:

· constants.xml – this contains parameters that the user will normally not need to change.

· feedstuff.xml – this contains the details of the crop products and feed items that can be made available to the livestock.

· fertMan.xml – this contains details of the chemical composition of fertilisers and manures.

· parameters.xml – this is the largest file and contains parameters covering all other aspects of the farm components.

The parameters are specific for the Agro-ecological zone selected by the user. However, it is possible to specify farm-specific parameter files by uploading them to the server using the Upload facility on the Farm tab (Fig 1).

Fig 1    The Farm tab

As indicated by the ‘xml’, the files are XML files. Details on how to edit these files is given below.

4.1 Parameter files

Details of the individual parameter files are given below. The parameters are sometimes arranged hierarchically into groups. Each group and parameter has a name, so in Fig 2 (from the parameter file feedstuff.xml), beneath each agro-ecological zone, there are parameters for a number of feedstuffs. These are arranged in a hierarchy, so that there are a large number of groups with the  name ‘feedItem’, each of which contains data on an individual feedstuff. Beneath this are other groups that describe the different characteristics of the feed. The lowest level in the hierarchy normally consists of a value, a unit and a description.

Fig 2    Example of XML hierarchy, shown with some groups expanded

This format is quite flexible; in some cases, parameter groups can appear more than once e.g. there will usually be a range of livestock types present within an agro ecological zone, whilst in other cases, more than one parameter group must be present e.g. the parameter group Month must appear 12 times in the parameters.xml file, since this group specifies the monthly climatic data. In the following tables, the name of the group immediately beneath the agro-ecosystem is referred to as Tag level 1, the next level as Tag level 2 etc.. If ‘*’ is inserted in the ‘>1’ column of the table, the group of parameters can or must appear more than once in the file.

4.2 Editing XML files

These are structured text files, so can be edited using any text editor. However, users may find that an editor that recognises the structural aspects of XML files may make editing easier. An editor was developed to enable the FarmAC parameter files to be edited. This is available from the web interface. Alternatively, there are a number of such programs available for free or at reasonable cost (e.g. XMLNotepad or Editpad Pro).

If using a standard text editor to edit XML files, then you should be aware that these files are structured using tags. In the following example, the tag ‘Identity’ is opened in the brackets <…> and closed again in the brackets <\..>.

 <Identity color="red">1</Identity>

Important note: some tags will appear more than once e.g. the Month tag must appear 12 times in parameters. xml. The Identity tag is used by the model to search for parameters in the sequence, so if more than one tag with the same name appears in the file, the values of the Identity tag must be in numerical order, starting with 1.

5 Appendix       Details of parameter files

5.1 Constants.xml

This file contains a diverse range of parameter values that the expert user will not normally need to change.

Tag level 1	Tag level 2	Description	Units	Example
humification_const		Proportion of degraded carbon that is partitioned to humus-like organic matter	0
alpha		Concentration of carbon in organic matter	none	0.46
spinupYearsBaseLine		Number of years that is used in Ctool spinup of scenario if using adaptation (only if spinup is used)	years	0
spinupYearsNonBaseLine		Number of years that is used in Ctool spinup of projection scenario (only if spinup is used)	years	0
absoluteGrazedDMtolerance		Threshold below which any difference between production and consumption of grazed feed item is ignored, irrespective of the percentage error	kg DM/ha	50
rgas		Universal gas constant	J/(mol K)	8.314
CNhum		C:N ratio of humus	none	12
tor		Proportion of manure C degraded that is emitted as methane	none	0.5
Eapp		Apparent activation energy	J/mol	112700
CO2EqCH4		CO2 equivalent of CH4-C (100 year)	kg CO2 equivalents/kg CH4-C	28
CO2EqN2O		CO2 equivalent of N2O-N (100 year)	kg CO2 equivalents/kg N2O-N	468.3
CO2EqsoilC		CO2 equivalent of carbon emitted as CO2 (100 year)	kg CO2 equivalents/kg C	3.667
IndirectNH3N2OFactor		Emission factor for N2O emission from redeposited NH3 emissions	kg N2O-N emitted/kg NH3-N emitted	0.01
IndirectNO3N2OFactor		Emission factor for N2O emission from leached NO3-N - IPCC (2006)	kg N2O-N emitted/kg NO3-N leached	0.0075
defaultBeddingCconc		Concentration of carbon in default bedding dry matter	kg C/kg DM	0.4
defaultBeddingNconc		Concentration of nitrogen in default bedding dry matter	kg N/kg DM	0.0064
InventorySystem		IPCC 2006	none	1
InventorySystem		FarmAC	none	2
ErrorToleranceYield		Maximum difference between expected and modelled DM yield of crops	none	0.02
ErrorToleranceGrazing		Maximum proportional difference between grazed crop DM and grazed crop intake	none	0.02
C-Tool		C-Tool parameters
	timeStep	Time step of model (normally one day)	year	0.00274
	NumOfLayers	Number of soil layers (currently not used i.e. fixed in code)	none	4
	FOMdecompositionrate	Decomposition rate of fresh organic matter	per year	1.44
	HUMdecompositionrate	Decomposition rate of humic organic matter	per year	0.0336
	ROMdecompositionrate	Decomposition rate of resistant organic matter	per year	0.000463
	fCO2	Proportion of degraded humic and resistant organic matter emitted as CO2	none	0.628
	ROMificationfraction	Proportion of degraded humic organic matter that is partitioned to resistant organic matter	none	0.012
	transportCoefficient	Proportion of degraded organic matter transported to next layer	none	0.03
EFNO3_IPCC		Leaching fraction - IPCC (2006)	kg N2O-N/kg manure N	0.3
fert_EFNH3_IPCC		Emission factor for NH3 and NOx - IPCC (2006)	kg NH3-N or NOx-N/kg fertiliser N	0.1
man_EFNH3_IPCC		Emission factor for NH3 and NOx - IPCC (2006)	kg NH3-N/kg manure N	0.2
adaptationTimePeriod		Minimum length of the period over which flows will be calculated when using adaptation mode	years	500
minimumTimePeriod		Minimum length of the period over which flows will be calculated when using projection mode	years	10
maximumIterations		Maximum number of iterations of crop production before model gives up and generates an error	none	50

5.2 Feedstuff.xml

This file contains the details of the crop products and feed items that can be made available to the livestock. Details of the chemical characteristics of locally-available feed items will usually be available from national livestock feeding tables. Most of these parameters will need to be altered when defining a new feed item.

Tag level 1	Tag level 2	Description	Units	Example	>1
feedItem					*
	FeedCode	Unique integer identifier
	Main	Is true if this item is the main product of the crop	none	FALSE
	Fibre_concentration	The concentration of lignin (=acid detergent fibre)	kg/kgDM	0.104
	NFE_concentration	Concentration of nitrogen-free extract (=sugar and starch)	kg/kgDM	0.069
	CrudeProtein_concentration	Concentration of crude protein (= 6.25 times nitrogen concentration)	kg/kgDM	0.515
	Fat_concentration	Concentration of fat	kg/kgDM	0.035
	Energy_concentration	Concentration of digestible energy	MJ/kgDM	16.3409
	Ash_concentration	Concentration of ash	kg/kgDM	0.073
	Nitrate_concentration	Nitrate concentration	kg/kgDM	0
	DMDigestibility	Dry matter digestibility	kg/kgDM	0.8
	Bedding_material	Is true if this item can be used as bedding	Boolean	FALSE
	processStorageLoss	Proportion of DM, C and N lost during processing or storage	-	0

5.3 FerMan.xml

This contains the details of the fertiliser and manure that can be imported to a farm. The composition of mineral N fertilisers will usually be standard for a particular country whereas the chemical composition of manure can vary widely. The data in this table are only used directly if manure is imported into the farm; the values for home-produced manure will be provided by the model.

Tag level 1	Tag level 2	Description	Units	Example
fertiliser
	Nconcentration	Concentration of nitrogen	kg N/kg fertiliser	0.335
	Cconcentration	Concentration of carbon	kg C/kg fertiliser	0
manure
	TANconcentration	Concentration of ammonium nitrogen	kg NH4-N/kg manure fresh weight	0.0033
	organicNconcentration	Concentration of organic nitrogen	kg organic-N/kg manure fresh weight	0.0007
	degCconcentration	Concentration of readily-degradable organic carbon degC	kg/kg manure fresh weight	0.009
	nonDegCconcentration	Concentration of resistant organic carbon	kg//kg manure fresh weight	0.009
	humicCconcentration	Concentration of humic carbon	kg/kg manure fresh weight	0

5.4 Parameters.xml

This contains parameters covering all other aspects of the farm components not dealt with in the other parameter files.

The main parameters to consider changing are:

· The SandFraction and ClayFraction in the SoilType group. These values can usually be obtained from local experts or soils databases.

·  The SoilWater group must contain 4 layerClass groups, representing layers of soil. The z_lower of each of these groups must be greater than the previous and the value of z_lower in the last of these represents the maximum depth of the soil.

· The initial of each type of farm (arable, pig, cattle). If in doubt, choose a value equal to half the soil organic matter content.

· The data in the Month group (For guidance on obtaining these data, see Climate data).

· The following data for livestock; isRuminant, isDairy, Liveweight, milkNconc, milkFatconc,  weightGainDairy Age and Mortality. The milkAdjustmentCoeff is used to adjust the modelled milk production to match measured values.

· The following data for housing; EFNH3housingTier2, feedWasteFactor, beddingFactor.

· The following data for manure storage; StoresSolid, EFNH3storageIPCC, EFN2OstorageIPCC.

· All crop data (For guidance, see Crop parameters).

· For manure applications; EFNH3FieldTier2 and NH3ReductionFactor.

· NumberRaindays (For guidance on obtaining these data, see Climate data).

Tag level 1	Tag level 2	Tag level 3	Tag level 4	Description	Units	Example	>1
SoilType				Type of soil		Coarse sandy soil	*
	N2Factor			Dinitrogen emission factor	kg N2-N/kg N2O-N emitted	3
	ThermalDiffusivity			Thermal diffusivity of soil	metres squared per second	9E-07
	SandFraction			Fraction of sand	kg/kg soil	0.95
	ClayFraction			Fraction of clay	kg/kg soil	0.034
	C-Tool			C-Tool parameters for arable soil
		InitialC		Initial carbon content in soil	kg/ha	85000
		InitialCtoN		Initial C:N ratio of soil	none	10
		InitialFOMinput		Annual input of fresh organic matter (FOM) to be used in model initialisation	kg C/ha/yr	1000
		InitialFOMCtoN		C:N ratio of FOM input to be used in model initialisation	none	15
		pHUMupperLayer		Proportion of humus organic matter (HUM) in topsoil	fraction	0.6
		pHUMlowerLayer		Proportion of humus organic matter (HUM) in subsoil	fraction	0.6
	SoilWater			Parameters for soil water model
		layerClass		Hydraulic characteristics of a soil layer (Identity = 1 for surface layer) Not currently used			*
			z_lower	Depth below the soil surface of the lower boundary of the layer	m	0.1
			fieldCapacity	Field capacity (maximum water holding capacity)	100 * cubic metre/cubic metre	40
		drainageConst		Rate at which water in excess of field capacity drains from any given layer	mm per day	0.4
Month				Monthly mean weather data			*
	AirTemperature			Average monthly air temperature 2 metres above ground	Celsius	27.6
	Precipitation			Average monthly precipitation	mm	0
	PotentialEvapoTrans			Average daily evapotranspiration for this month	mm per day	5.69
GrazingMidpoint				Midpoint for grazing	Day	180
AverageAirTemperature				Average annual air temperature 2 metres above ground (used only if monthly averages are not available)	Celsius	15
AirTemperatureMaxDay				Julian day when air temperature is at its maximum  (used only if monthly averages are not available)	Days	105
AirTemperaturAmplitude				Maximum deviation of air temperature from the mean (used only if monthly averages are not available)	Celsius	15.1
Livestock				Details of livestock			*
	SpeciesGroup			To which species group livestock belongs (1 = cattle, 2 = pigs)	1
	efficiencyProteinMilk			The efficiency with which dietry protein is converted to milk protein	0.7
	LivestockType			Subdivision of species group	1
	isRuminant			true if the livestock are ruminants	none	TRUE
	isDairy			true if the livestock are dairy animals	none	FALSE
	Liveweight			Mean live weight of livestock	kg	300
	mu_base			Energy intake below which there is no reduction in utilisation of energy	Proportion per unit of energy intake, normalised by maintenance energy demand	0.25
	mu_b			Rate of reduction in energy utilisation with increasing energy intake	Proportion per unit of energy intake, normalised by maintenance energy demand	0
	milkCconc			Concentration of carbon in milk	kg/kg	0.05
	milkNconc			Concentration of nitrogen in milk	kg/kg	0.00512
	milkFat			Concentration of fat in milk	g/kg	50
	growthNconc			Concentration of nitrogen in animal growth	kg/kg	0.026
	growthCconc			Concentration of carbon in animal growth	kg/kg	0.232
	maintenanceEnergyCoeff			Coefficient in calculation of maintenance energy requirement	none	1.2
	growthEnergyDemandCoeff			Energy requirement per unit growth	MJ/kg	24.3
	milkAdjustmentCoeff			Increases (>1) or decreases (<1) the energy required to produce a litre of milk	none	1
	urineProp			Proportion of carbon in diet is excreted in urine	kg/kg	0.04
	weightGainDairy			Weight gain of dairy animals	kg per year	0
	HousedDuringGrazing			Is true if animals are housing during part of the day when grazed	None	FALSE
	Age			Mean age of livestock	years	6
	entericTier2MCF			Methane conversion factor	kg methane per MJ energy intake	0.07
	Mortality			Proportion of livestock dying on the farm	-	0.029
	nitrateEfficiency			Efficiency with which nitrate in feed reduces enteric methane emissions	kg methane oxidized per kg nitrate	0.8
Housing				Details of livestock housing			*
	HousingRefTemp			Reference temperature for ammonia emission factor (Tier 3 - not currently used)	Celsius	10
	EFNH3housingRef			Ammonia emission factor for housing (Tier 3 - not currently used)	kg ammonia N/kg ammonium in housing	0.294
	EFNH3housingTier2			Ammonia emission factor for housing (Tier 2)	kg ammonia N/kg ammonium in housing	0.2
	feedWasteFactor			Proportion of feed dry matter that is wasted in housing (enters manure)	kg DM/kg DM	0.15
	ProportionDegradable			Proportion of degradable carbon partitioned to solid manure storage, if more than one manure store is used	0
	ProportionNondegradable			Proportion of non-degradable carbon partitioned to solid manure storage, if more than one manure store is used	0
	ProportionTAN			Proportion of ammoniacal N partitioned to solid manure storage, if more than one manure store is used	0
	beddingFactor			Rate of use of bedding dry matter	kg dry matter/animal/day	0
ManureStorage				Details of manure storage			*
	StoresSolid			Is true if this storage stores solid manure	TRUE
	b1			Coefficient in manure carbon degradation (Tier 3 - not currently used)	None	1
	lnArr			Log natural in Arrhenius equation	None	40
	meanTemp			Mean air temperture during storage period	Celsius	28.079
	Bo			Methane producing capacity	cubic metres methane/kg volatile solids	0.24
	ohmTAN			Proportion of manure TAN lost by runoff or leaching	None	0
	ohmOrg			Proportion of manure lost by runoff or leaching	None	0.05
	EFNH3storageRef			Ammonia emission factor	kg/kg	0.032
	MCF			methane conversion factor	none	0.035
	EFNH3storageIPCC			Ammonia emission factor IPCC system	kg/kg	0.8
	EFN2OstorageIPCC			N2O emission factor IPCC system	kg/kg	0.02
	EFN2OstorageRef			N2O emission factor nonIPCC system	kg/kg	0.02
	lambda_m			N2 emissions as a multiple of N2O emissions	none	3
	StorageRefTemp			Reference temperature for ammonia emission factor	Celsius	10
	PropGasCapture			Proportion of gaseous emissions captured	None	0
	TypeStored			Type of manure stored	2
Crop				Details of crops			*
	NfixationFactor			Rate of reduction in N fixation with increasing mineral N availability	kg N/kg mineral N available	-1
	HarvestMethod
		PropAboveGroundResidues		Above-ground yield of dry matter that cannot be harvested	kg DM/kg DM	0.11
	PropBelowGroundResidues			The below-ground crop residues (e.g. roots), as a proportion of the DM yield	kg DM/kg DM	0.24
	BelowGroundCconc			Carbon concentration in below-ground dry matter	none	0.47
	MaximumRootingDepth			Maximum rooting depth, if not restricted by soil depth	metres	2
	BelowGroundCtoN			Ratio of carbon to nitrogen in below-ground dry matter	none	33
UrineNH3EF				Urine NH3 emission factor	kg NH3-N/kg urine N	0.15
CropResidues				Emission factors for crop residues
	EFN2O			Nitrous oxide emission factor for crop residues	kg N2O-N/kg N	0.01
	EFN2O_burning			Nitrous oxide emission factor for burnt crop residues (Table 2.5 Guidelines V4_02_Ch2_Generic.pdf)	kg N2O-N/kg DM	0.00007
	EFNOx_burning			NOx emission factor for burnt crop residues from Guidebook (assume as NO2)	kg N2O-N/kg DM	0.0025
	EFNH3_burning			Ammonia emission factor for burnt crop residues from Guidebook	kg NH3-N/kg DM	0.0013
	EFBlackC_burning			Black carbon emission factor for burnt crop residues from Guidebook	kg C/kg DM	0.0005
	EFCO_burning			CO-C emission factor for burnt crop residues from Guidebook	kg NH3-N/kg DM	0.0286
MineralisedSoilN				Emission factors for mineralised soil N
	EFN2O			Nitrous oxide emission factor	kg N2O-N/kg N	0.01
Fertiliser				Emission factors for fertilisers
	EFN2O			Nitrous oxide emission factor	kg N2O-N/kg N	0.01
	EFN2O_IPCC			Nitrous oxide emission factor	kg N2O-N/kg manure N	0.01
	FertiliserType			Details of emission factors for a specific type of nitrogen fertiliser			*
		EFNH3		Ammonia emission factor	kg NH3-N/kg N	0.02
Manure				Emission factors for manures
	EFN2O			Nitrous oxide emission factor	kg N2O-N/kg manure N	0.01
	EFN2O_IPCC			Nitrous oxide emission factor	kg N2O-N/kg manure N	0.005
	N2Factor			Dinitrogen emission factor	kg N2-N/kg N2O-N emitted	3
	ManureType			Details for individual manure type			*
		EFNH3FieldRef		Reference ammonia emission factor	kg/kg	0.15
		EFNH3FieldTier2		Reference ammonia emission factor	kg/kg	0.2
		EFNH3FieldRefTemperature		Temperature for reference ammonia emission factor	Celsius	15
ManureApplicationTechnique				Details for individual manure application method			*
	NH3ReductionFactor			Reduction in ammonia emission relative to broadcast spreading	none	0
NumberRaindays				Total number of rainy days per year	80

5.5 Sources

5.5.1 Climate data

The parameter NumberRainDays is used to divide rainfall into a discrete number of rainfall events. Over-estimating the number of events will tend to increase drainage whereas an under-estimation will tend to over-estimate evaporation. It is preferable to focus on those events that contribute significantly to the input of water (i.e. events where precipitation is above about 10 mm day^-1). Data describing the number of days with significant rainfall may be available locally. If not, the paper by Sun et al (2006; http://dx.doi.org/10.1175/JCLI3672.1) may be of assistance.

Monthly climate data can be obtained for many locations from FAO.

First, download and install Climwat (http://www.fao.org/nr/water/infores_databases_climwat.html).

Step 1

Run Climwat.

Step 2

Choose your country.

Step 3

Choose your location.

Step 4

Choose Export selected stations and download the files:

Step 5

Open the .pen file. The first row of numbers contains data for January, the second row February etc. The first column contains the minimum air temperature and the second contains the maximum (both in Celsius). Calculate the air temperature as the average of the maximum and minimum values.

Step 6

Open the .cli file. The rows contain the monthly data. The first column contains the potential evapotranspiration, the second he precipitation (both in mm d^-1).

5.5.2 Crop parameters

The above- and below-ground crop residues are the main sources of C input to the soil model. The above-ground residues consist of those residues that are deposited onto the soil surface before the harvesting date (mainly senescent leaves and tiller death due to self-thinning) and those that are deposited at the time of harvesting (stubble, dust, small straw particles and uncollected straw/cut roughage). The below-ground residues consist of roots and root exudates.

The value of the maximum rooting depth (MaximumRootingDepth) should be set after discussion with local crop experts.

The value of the C content in below ground DM (BelowGroundCconc) can be estimated as 0.46 kg C (kg DM)^-1.

Based on Danish research, we recommend the values shown in Table 1.

Table 1            Parameters determining the above and below ground crop residues

Crop types	Stubble*	Residues deposited prior to harvest	PropAboveGroundResidues ****	PropBelowGroundResidues ****
	Proportion of yield of main and secondary products
Cereals	0.15	0.35	0.5	0.38
Root crops	0.06	0.01	0.07	0.14
Grass and grass/clover**	0.15	0.27	0.42	1.17
Whole-crop cereal silage	0.16	0.18	0.34	0.45
Trees and shrubs***	0.07	0.07	0.11	1.11

* for trees and shrubs, this is the stump mass

**grass grown to maturity (heading) should be parameterised as if it were a cereal crop

*** if no foliage or wood is removed, use ‘incorporation’ to add them to the soil

***these parameters can be found in the FarmAC parameters.xml file, under each crop

Table 2            Standard values of below-ground C:N to use in FarmAC

Crop	Root C:N*
Grass and cereals	33
White clover	13
Other legumes	18
Trees and shrubs	60

* the parameter BelowGroundCtoN can be found in the FarmAC parameters.xml file, under each crop