Abstract
Over the past half-century, crop rotations have become increasingly simplified, with whole regions producing only one or two crops in succession. Simplification is problematic from a weed management perspective, because it results in weeds’ repeated exposure to the same set of ecological and agronomic conditions. This can exacerbate weed infestations and promote the evolution of herbicide resistance. Diversifying crop rotations through addition of crop species and their associated managements may suppress weeds and reduce selection pressure for herbicide resistance by altering stress and mortality factors affecting weed dynamics. Here we report the results of a meta-analysis using 298 paired observations from 54 studies across six continents to compare weed responses due to simple and more diverse crop rotations. We found diversifying from simple rotations reduced weed density (49%), but did not have a significant effect on weed biomass. We investigated the effect of management practices, environmental factors, and rotation design on this effect. Diversification that increased the variance around crop planting dates was more effective in suppressing weeds than increasing crop species richness alone. Increasing rotational diversity reduced weed density more under zero-tillage conditions (65%) than tilled conditions (41%), and did so regardless of environmental context and auxiliary herbicide use. Our findings highlight the value of diversifying crop rotations to control weed populations, and support its efficacy under varied environmental conditions and management scenarios.
Highlights
Weed management is an essential part of crop production
While the shifts in crop and weed management practices have been generally effective in controlling weeds and minimizing labor costs, heavy reliance on herbicides has led to adverse
Diversification of crop rotations significantly reduced weed density compared to simple rotations (Fig 2), with a mean reduction of 49% (n = 247, p < 0.001)
Summary
Weed management is an essential part of crop production. Crop yield reductions from weeds average 40% on a global scale, and costs associated with management inputs represent a major economic expense for farmers [1, 2]. Many major agricultural regions produce only one or two economically-important crops [3]. This reduction of crop rotational diversity has been largely due to the adoption of herbicides and herbicide-resistant crops [4, 5]. While the shifts in crop and weed management practices have been generally effective in controlling weeds and minimizing labor costs, heavy reliance on herbicides has led to adverse.
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