lfert: Land Fertility
Variable
Agricultural sector
Land Fertility [Veg eq kg/(year*hectare)]
lfert = lfert + dt*( lfr - lfd )

lfert in the updating graph: ( how to read )
In nodes
lferti : initial land fertility
lfd : land fertility degredation
lfert : Land Fertility
lfr : land fertility regeneration
Out nodes
ly : land yield
lfd : land fertility degredation
lfert : Land Fertility
lfr : land fertility regeneration