Effects of hoeing and rototilling on some aspects of the population dynamics of pure stands of Portulaca oleracea L. (purslane)

Two naturally-established pure stands of Portulaca oleracea L. were used to study the effects of five disturbance schedules (early, midseason, late, repeated and no disturbance) on the development of purslane populations. In one stand disturbance was by rototilling and in the second stand by hoeing. In most disturbed plots, the re-established stands had densities which were not significantly less than those of the control plots. These stands were composed of plants established by seed germination (seed plants) and by regeneration of roots on severed stems (stem plants) or shoots on root and stem bases (root plants). The composition of these stands depended on the type of disturbance. Undisturbed stands were composed predominantly of seed plants. Disturbed stands had fewer than 55% seed plants. Hoeing resulted in a greater proportion of stem plants and a lower proportion of root plants than rototilling. All disturbances resulted in decreased dry matter yields per unit area. The maximum yields for the controls in the two stands were similar, regardless of differences in density, mean dry weight, size class distribution and time of establishment. Early disturbance resulted in significant decreases in seed capsule production while disturbance late in the season had minimal effects on seed production. The implications for control of purslane in crops are discussed.