Interference between Mayweed Chamomile (Anthemis cotula) and Pea (Pisum sativum) is Affected by Form of Interference and Soil Water Regime

Abstract

Effects of root-shoot interference, soil water regimes, and soil nitrogen were evaluated to determine aggressivity for pea relative to mayweed chamomile in the greenhouse using replacement series experiments. Interference between pea and mayweed chamomile occurred mainly below ground, and soil water was more important than soil nitrogen in controlling the outcome of interference. Pea was a stronger competitor than mayweed chamomile under all conditions investigated. Leaf area, root weight, and shoot weight of mayweed chamomile were reduced 55 to 87% by full interference and 27 to 60% by root only interference from pea. Full interference from mayweed chamomile for 53 days after planting released the remaining pea from intraspecific interference and it grew 80% larger and produced 100% more pod weight compared to a pea in monoculture. Low soil water potential (–175 kPa) compared to high water potential (–33 kPa) reduced the height, leaf area, and shoot weight of pea in 1:1 mixtures, but had no effect on mayweed chamomile. Decreasing soil water increased the aggressivity of mayweed chamomile relative to pea. Nitrogen added at 20 mg wk-1compared to no added nitrogen had no effect on peas, but more than doubled the size of mayweed chamomile in monoculture and in mixtures with pea. Added nitrogen did not increase the aggressivity of mayweed chamomile relative to pea.