Understanding spatial distribution has become increasingly important in weed science. Seed dispersal, both between and within agricultural fields, is an important component of weed spatial distribution. Analysis of the effect of dispersal between fields has been relatively neglected in theoretical studies of weed population dynamics. In this paper, we present a simple landscape-level model of the influence of seed dispersal on winter wild oat population dynamics between fields. In the model, two fields are interconnected, with seeds being carried from one field to another as would occur when seeds are carried by field equipment or in irrigation water. The model is intended to characterize the effect of field-level weed management decisions on landscape-level weed population dynamics. Three scenarios were studied. The first employed no control measures in either field. The second employed annual application of herbicides in field 1 with field 2 receiving no treatment. In the third scenario, an herbicide application took place in field 1 only if the weed population in that field exceeded an action threshold. In the first scenario, the net result of the immigration and emigration processes determined the increase or decrease of the stable plant population. In the second scenario, weeds in the controlled field (field 1) were not driven to extinction as might be expected. The weed populations grew for practically all the dispersal parameter space. Each change in the parameter's values produced a new stable equilibrium. This situation might correspond to a multiplicity of stable states. The uncontrolled field (field 2) experienced an indirect control effect due to the use of control measures in field 1. In the third scenario, we observed an interesting behavior of the populations in both fields. The population in field 1 was not driven under the economic threshold, and both fields showed complex dynamics within defined combinations of migration and emigration values.
Nomenclature: Sterile oat; Avena sterilis L.