Crop-Weed Competition & Yield Loss

Field Conditions

Weed density 20 /m²

Weed emergence timing 0 d

Crop planting density 8 /m²

Herbicide / mechanical control 0%

Season Readout

Day after crop emergence

0 d

Effective weed density

20.0 /m²

Yield loss

0.0%

Projected yield

0.00 t/ha

How it works

Yield loss from weed competition is modelled with the rectangular-hyperbola relation of Cousens (1985), the standard model in weed science for density-dependent crop loss:

YL(%) = i·x / (1 + i·x/A)
x = effective weed density (weeds/m²)
i = % loss per weed/m² as x → 0 (early competitive ability)
A = maximum % loss as x → ∞ (asymptote)

Two things this simulator lets you vary map directly onto the model:

Emergence timing sets i. Weeds that emerge before or with the crop intercept light and root volume first and compete far more strongly than weeds that emerge later — this is the agronomic basis of the "critical period of weed control." Here i is highest for early-emerging weeds and decays roughly exponentially the later weeds appear.
Crop planting density sets A. A denser crop stand closes its canopy sooner, shading out weeds before they can fully establish, which lowers the maximum possible loss — a real density-compensation effect seen in row crops like maize and soybean.
Herbicide / mechanical control scales the raw weed density down to an effective density x before it enters the formula, exactly as a partial-efficacy treatment would in the field.

The 3D field shows crop plants (green) and weeds (amber) growing over a simulated season using logistic growth curves gated by each species' emergence day, so you can watch the canopy race that the formula summarizes numerically.

Crop canopy Weeds

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