Abstract
(1) A statistical model is presented which allows the exploration of the effects of weed patchiness on crop yield. Input data are a non-linear regression for yield versus weed density, and the parameters of a frequency distribution. (2) Simulation are presented for yield estimation assuming either a random or a negative binomial distribution. The assumption of a random distribution under-estimated yields in the presence of aggregation, and the discrepancy increased with the degree of aggregation. (3) In an example with Bromus sterilis in winter wheat, it was concluded that although estimates of yield may be in error at high weed densities, the error at densities where practical control decisions would be made are minimal. However, weed distribution may still contribute to decisions relating to weed control priorities.