A

Index for the most limiting environmental factor of the nitrification (range 0-1) (units: --)

ADD

Amount of residue carbon to be added to FOM in the soil layer under consideration (units: kg [C] / ha)

ANH4

Total extractable ammonium N in soil profile (units: kg [N]/ha)

ANO3

Total extractable nitrate N in soil profile (units: kg [N]/ha)

AINH4

Sum of SNH4 across all layers (units: kg [N] / ha)

AINO3

Sum of SNO3 across all layers (units:kg [N] / ha )

AK

Maximum hydrolysis rate of urea (i.e. proportion of urea that will hydrolyze in 1 day under optimum conditions). AK >= 0.25. (units: --)

AMTRES

Total amount of residue applied to the soil (units: kg [residue] / ha)

AMTSRF

Ttotal amount of residue applied to the surface litter layer (units: kg [residue] / ha)

ANDEM

Crop N demand (units: kg [N] / ha)

ANH4

Total extractable ammonium N in soil profile (units: kg [N] / ha)

ANO3

Total extractable nitrate N in soil profile (units: kg [N] / ha)

B2

Maximum amount of NH4 that may nitrify (units: )
Also: amount of NH4 that will nitrify

BB

Maximum nitrification rate (units: kg [N] / (ha . d))
Also: Fraction of NH4 that will nitrify

BD

Bulk density (units: g / cm³)

CNI

Index indicating the capacity for nitrification to proceed (range: 0-1) (units: )

CNR

C/N ratio of FOM (units: --)

CNRF

CN ratio factor: the effect of C/N ratio on SOM decomposition (range 0-1) (units: --)

CW

Water extractable (water soluble) SOM carbon (units: ug [C] / g [soil])

DAP

Number of days after planting (units: --)

DEPTH

Depth to the bottom of a layer, measured from the soil surface (units: cm)

DEPRES

Residue incorporation depth (units: cm)

DLAYR

Depth increment of a soil layer (units: cm)

DMINR

Maximum decomposition rate constant of stable organic matter (units:1 / d)

DMOD

Factor to adjust the mineralization rate RHMIN for certain atypical soils (range 0-1) (units: --)

DNG

N demand for potential new top growth (units: kg N / (ha . d))

DNRATE

Denitrification rate (units: kg [N] / (ha . d))

DOY

Day of the year (units: Julian days)

DRESMG

Residue application depth (with the option of automatic residue application) (units: cm)

DUL

Drained upper limit of soil water content (units: volume fraction)

ELNC

Environmental limit on nitrification capacity: depends on water, temperature and NH4 level (range 0-1) (units: --)

ESW

Extractable soil water of a soil layer (units: volume fraction)

FAC

Conversion factor to switch from kg N / ha to ug N / g soil

FDAY(J)

Day of the year when fertilizer application J was made (units: Julian days)

FLUX

Downward water movement between soil layers due to drainage (units: cm)

FNH4

NH4 availability factor (range 0-1) (units: --)

FNO3

NO3 availability factor (range 0-1) (units: --)

FOM

Fresh organic residue (units: kg [residue] / ha)

FON

Nitrogen in fresh organic matter (units: kg [N] / ha)

FPLACE

Subroutine on fertilizer application

FPOOL

FOM pool: 1=carbohydrate, 2=cellulose, 3=lignin (units: kg [residue pool] / ha)

FR

Residue fraction to be added to the soil layer under consideration (units: --)

FT

Temperature factor for denitrifcation rate (range 0-1) (units: --)

FW

Soil water factor: effect of soil water content in the range from SAT to DUL on the denitrification rate (range 0-1) (units: --)

G1

Decay rate of a FOM pool (units: proportion of the pool that decays in 1 day)

GRCOM

Amount of residue decomposed from the three FOM pools (units: kg [residue] / ha)

GRNOM

Gross mineralization of N associated with FOM decomposition (units: kg [N] / ha)

HOLD

Temporary variable holding the depth of the top of a soil layer (units: cm)

HUMC

Carbon in stable organic matter (units: kg [C] / ha)

HUMN

Nitrogen in stable orgnaic matter (units: kg [N] / ha)

ICREN

N concentration in the intial amount of residue applied (units: %)

ICRES

Initial residue application (units: kg [residue] / ha)

IFLAG

Flag for N source: 1 = urea; 2 = NO3 (units: --)

IFTYPE

Code number for fertilizer type (units: --)

INCDAT

Incorporation date of previously added residue (units: Julian days)

INCDEP

Incorporation depth of previously added residue (units: cm)

INCPER

Incorporation percentage of previously added residue (units: --)

INIT

Flag indicating first-time calculations (units: --)

IOUT

Flag that determines when to jump out of a DO loop (units: --)

IRESI

Flag parameter that indicates which residue application method is followed. A = Automatic residue application at a certain days after planting for multiple years; N = No residue; R = On reported dates; D = As reported, in DAP; F = Auto, with fixed amounts. (units: --)

IUOF

Critical Julian day when all urea is assumed to be hydrolyzed (this is assumed to occur 21 days after the urea application) (units: --)

IUON

Flag parameter set to TRUE when urea is present. (units: --)

JP

FOM pool number (units: --)

LL

Lower limit of soil water content (units: volume fraction)

METRES

Residue application method (not used yet in the model) (units: --)

MF

Moisture factor: the effect of soil water content on SOM decomposition (range 0-1) (units: --)

NAPRES

Number of residue applications done (units: --) *** CHECK ***

NH4

NH4 concentration of a soil layer (units: ug [N] / g [soil])

NLAYR

Number of layers in soil (units: --)

NNOM

Net N release from all SOM sources (units: kg [N] / ha)

NO3

Nitrate concentation of a soil layer (units: ug [N] / g [soil])

NOUT

Amount of nitrate lost from a soil layer by leaching (units: kg [N] / ha)

NRESAP

Number of residue applications to be done *** CHECK ***

NRESDL

Number of days after planting that residues are applied (with the option of automatic residue application) (units: --)

NTRANS

Subroutine that simulates the decay of SOM and the subsequent mineralization / immobilization of N, the nitrification of ammonium, and denitrification. Also includes fertilizer addition and urea hydrolysis.

OC

Organic carbon content of layer (units: %)

PH

soil pH (units: --)

PHN

Factor for pH effect on nitrication rate (range 0-1) (units: --)

RDCEL

Maximum decomposition rate of cellulose (units: )

RDCHO

Maximum decomposition rate of carbohydrates (units: )

RDLIG

Maximum decomposition rate of lignin (units: )

RDECR(13)

Decay rate for various FOM fractions (units: )

RESDEP

Depth of incorporation of residues (units: cm)

RESAPP

Carbon content of the newly applied residue (units: )

RESCOD

FileX code for residue type (not used yet) (units: --).

RESDAY

Day at which residues are applied (units: Julian days)

RESDEP

Residue incorporation depth (units: cm)

RESIDUE

Amount of residue applied (units: kg [residue] / ha)

RESN

N concentration of the residue (units: %)

RESNIT

N concentration of the residue (units: %)

RESSOL

Sum of all the residue applications to the soil (units: kg [residue] / ha)

RESSRF

Sum of all the residue applications to the surface litter layer (units: kg [residue] / ha)

RHMIN

N mineralization from HUM (units: kg [N] / ha)

RINP

Residue incorporation percentage (units: %)

RIP

Residue incorporation percentage (with the option of automatic residue application) (units: %)

RNAC

N immobilization rate associated with residue decomposition (units: kg [N] / (ha . d))

RNH4U

Potential ammonium uptake from a layer (units: kg [N] / ha)

RNO3U

Potential nitrate uptake from a layer (units: kg [N] / ha)

RNTRF

Nitrification rate (units: kg [N] / (ha . d))

RP2

Nitrification capacity index based on the conditions during the immediate past, i.e. last two days (range 0-1) (units: --)

SANC

Effect of supply of ammonium on nitrification capacity (units: )

SARNC

Effect of supply of ammonium on the reduction of nitrification capacity for the next day (range 0-1) (units: )

SAT

Saturated soil water content (units: cm³ [H₂O] / cm³ [soil]))

SNH4

NH4 content of a soil layer (units: kg [N] / ha)

SNO3

Amount of NO3 present in a soil layer (units: kg [N] / ha)

SOILC

Soil carbon (= 58% of HUM) (units: kg [C] / ha)

ST

Soil temperature of a soil layer (units: ^oC)

SW

Volumetric water content of soil (units: cm³ / cm³)

SWEF

Soil water evaporation fraction. The fraction of the LL water content that determines the lowest possible value the top soil layer water content can become by soil evaporation. The value depends on the depth of the first layer.

TANC

Actual N concentration in plant tops (units: g [N] / g [DW])

TF

Temperature factor: the effect of temperature on urea hydrolysis (range 0-1) (units: --)

TF1

Temperature factor: the effect of temperature on SOM decomposition or nitrification (range 0-1) (units: --)

TFY

Yesterdays temperature factor (range 0-1). (units: --) *** CHECK ***

THUMN

Sum of HUMN across all soil layers (units:kg [N] / ha )

TIFOM

Sum of FOM across all soil layers (units: kf [residue] / ha )

TIFON

Sum of FON across all soil layers (units: kg [N] / ha)

TNDEM

N demand of plant tops (units: kg [N] / ha)

TNOX

Nitrous oxide (NO_x) pool of the air (units: )

TNOXI

TNOX initial value (units: )

TOPWT

Weight of plant tops (units: kg / ha)

TOTIN

Mineral N in the soil (units: kg [N] / ha)

TOTN

Mineral N present at initialization (units: ug [N] / g [soil])

TSIN

Total amount of N (NH4 + NO3) across all layers (units: )

TSOC

Sum across all soil layers of carbon in stable organic matter (HUMC) (units: kg [C] / ha)

TSON

Sum across all soil layers of N in stable organic matter (HUMN) (units: kg [N] / ha )

UHYDR

Rate of urea hydrolysis (units: kg N / (ha . d))

UPPM

Urea concentration ofa soil layer (units: ug [N] / g [soil])

UREA

Amount of urea in a layer (units: kg [N] / ha)

WFD

Water factor: effect of soil water on nitrification rate (range 0-1) (units: --)

WFY

Available water as fraction of field capacity *** CHECK ***
Or: Yesterdays water factor (range 0-1). *** CHECK ***

X

Temporary variable that stores the fraction of carbohydrate, cellulose, or lignin in FOM, before the decomposition is done. (units: )

XL

Excess water (above DUL) as a fraction of the maximum amount of excess water (i.e. saturated). (units:--)

XMIN

Amount of NH4 that cannot be immobilized but stays behind in the soil as NH4 (units: )
Also: amount of NO3 that cannot denitrify but stays behind in the soil as NO3.

XT

Temperature effect on nitrification capacity (units: --)

XW

Water effect on nitirification capacity (units: --)