Chemical Leaching Loss Calculator

Estimates how much dissolved chemical (nitrate-N, for example) leaches below the root zone in a single irrigation, from a catch-can uniformity test and a soil water deficit — the kind of back-of-envelope check a grower or agronomist would run before a fertigation event, or to explain a nitrate monitoring result.

Calculator

Mean depth infiltrated (d_z)

Irrigated area (A)

Results are reported per acre regardless of this value — it only matters if you want the total for a specific field size.

Christiansen's uniformity coefficient (CU)

From a catch-can test — see the Catch-Can Uniformity Calculator.

Enter the low-quarter depth (d_LQ) directly instead of DU

Distribution uniformity (DU)

Low-quarter depth (d_LQ)

Soil water deficit (SWD)

Chemical concentration in leachate (C)

ppm

About this calculator

Deep percolation — and whatever is dissolved in it — comes from two sources: nonuniform infiltration (V_dp1) and over-application beyond the soil water deficit (V_dp2). F₁ (interpolated from Table 5.1) is an empirical factor relating CU to the fraction of infiltrated water lost to nonuniformity, assuming a 90%-adequacy, normally distributed application.

V_dp1 = d_zA(1−F₁) — V_dp2 = 0.95A(d_LQ−SWD) if d_LQ>SWD, else 0

V_dp = V_dp1+V_dp2 — d_p = V_dp/A — C_l = 0.226 × C × d_p

Table 5.1 only tabulates F₁ for CU between 70 and 98. Outside that range this tool will warn rather than guess by extrapolating.

Textbook Example 5.5: Using Example 5.1's field (d_z=2.0 in, CU=84% → F₁=0.71, d_LQ=1.5 in) with SWD=1.2 in and C=20 ppm: V_dp1=0.58 ac-in, V_dp2=0.29 ac-in, V_dp=0.87 ac-in, d_p=0.87 in, C_l=3.9 lb/ac. Click "Load textbook Example 5.5" above to see it worked through.