COS 72-5
Soil disturbance and ground cover: How weed communities and weed seed predators respond to tillage and cover crop residue in organic agricultural systems
Plant and animal communities can be influenced by ground cover and disturbance, factors frequently manipulated in agricultural systems. Conventional agricultural techniques are often highly disruptive to soil and ground cover. Organic agricultural techniques, which prohibit the use of synthetic chemicals to control pests and competitors, often reduce mechanical disturbance to encourage soil health and maintain weed-suppressing ground cover. Weed presence is of particular interest in agricultural systems. We report results from two separate experiments addressing the effect of soil disturbance (tillage) and ground cover (cover crop residue) on non-crop plant density, non-crop seed density, and non-crop seed removal. The first experiment planted sweet corn (Zea mays) into plots with a range of disturbances influencing ground cover: conventional till with bare ground, conventional till with plastic cover, conservation strip till, and conservation no till. The second experiment planted crookneck squash (Cucurbita pepo) into plots with different levels of ground cover, where all plots received identical strip till disturbance. We measured weed density, weed seed density, and weed seed removal by seed predators.
Results/Conclusions
In the first experiment, weed abundance was lowest and weed seed removal greatest under low disturbance/high ground cover. Conversely, weed abundance was greatest and weed seed removal lowest under high disturbance/low ground cover. While weed seed density was somewhat reduced under high disturbance, these effects were not significant. In the second experiment, which represents a different range of ground cover treatments, weed abundance was greatest under low ground cover. No treatment in this experiment significantly influenced weed seed density or weed seed removal.
These results suggest that ground cover alone can reduce non-crop plant density (experiment 2); this effect was also present when cover was not natural and disturbance was high (experiment 1). However, weed seed predation was most encouraged by natural cover (experiment 1). Weed seed density, while not significantly different among treatments, showed an interesting negative trend under high disturbance. Due to the long-term nature of seedbank responses, we will continue monitoring the weed seedbank for the three-year course of these experiments. We conclude that natural or synthetic ground cover will suppress current weed density, but natural cover and reduced disturbance may be most effective at suppressing future weed density by influencing weed seed presence.