Lw_(n) = allowable annual hydraulic loading rate based upon nitrogen limits in inches per year

Cp = total nitrogen concentration in soil solution in milligrams per liter. The soil solution contains small but significant quantities of soluble inorganic and organic compounds, some of which contains elements that are essential for plant growth.

Pr = precipitation rate in inches per year

ET = evapotranspiration rate in inches per year,

U = nitrogen uptake by crop in pounds per acre per year

4.4 = combined conversion factor

Cn = total nitrogen concentration in wastewater at time of application to land in milligrams per liter

f = fraction of applied nitrogen removed by denitrification and volatilization and assumed to be 0.20.