Maturity

Plant maturity is reached when the fraction of potential heat units accumulated, $fr_{PHU}$, is equal to 1.00. Once maturity is reached, the plant ceases to transpire and take up water and nutrients. Simulated plant biomass remains stable until the plant is harvested or killed via a management operation.

Table 5:2-1: SWAT+ input variables that pertain to optimal plant growth.

Variable Name	Definition	Input File
EXT_COEF	$k_l$: Light extinction coefficient	crop.dat
BIO_E	$RUE_{amb}$: Radiation use efficiency in ambient CO$_2$((kg/ha)/(MJ/m$^2$))	crop.dat
CO2HI	CO$_{2hi}$: Elevated CO$_2$ atmospheric concentration (ppmv)	crop.dat
BIOEHI	$RUE_{hi}$: Radiation use efficiency at elevated CO$_2$ atmospheric concentration value for CO$_{2hi}$((kg/ha)/(MJ/m$^2$))	crop.dat
MAT_YRS	$yr_{fulldev}$: The number of years for the tree species to reach full development (years)	crop.dat
BMX_TREES	$bio_{fulldev}$: The biomass of a fully developed tree stand for the specific tree species (metric tons/ha)	crop.dat
WAVP	$\Delta rue_{dcl}$: Rate of decline in radiation-use efficiency per unit increase in vapor pressure deficit (kg/ha⋅(MJ/m$^2$)$^{-1}$⋅kPa$^{-1}$or(10$^{-1}$ g/MJ)⋅kPa$^{-1}$)	crop.dat
PHU	$PHU$: potential heat units for plant growing at beginning of simulation (heat units)	.mgt
HEAT UNITS	$PHU$: potential heat units for plant whose growth is initiated in a planting operation (heat units)	.mgt
FRGRW1	$fr_{PHU,1}$: Fraction of the growing season corresponding to the 1st point on the optimal leaf area development curve	crop.dat
LAIMX1	$fr_{LAI,1}$: Fraction of the maximum plant leaf area index corresponding to the 1st point on the optimal leaf area development curve	crop.dat
FRGRW2	$fr_{PHU,2}$: Fraction of the growing season corresponding to the 2nd point on the optimal leaf area development curve	crop.dat
LAIMX2	$fr_{LAI,2}$: Fraction of the maximum plant leaf area index corresponding to the 2nd point on the optimal leaf area development curve	crop.dat
CHTMX	$h_{c,mx}$: Plant’s potential maximum canopy height (m)	crop.dat
BLAI	$LAI_{mx}$: Potential maximum leaf area index for the plant	crop.dat
DLAI	$fr_{PHU,sen}$: Fraction of growing season at which senescence becomes the dominant growth process	crop.dat
SOL_ZMX	$z_{root,mx}$: Maximum rooting depth in soil (mm)	.sol
RDMX	$z_{root,mx}$: Maximum rooting depth for plant (mm)	crop.dat