Abstract
Amaranthus hybridus is a noxious weed in Ontario, with demonstrated allelopathic properties that can lead to decreased agricultural production. We tested the germination and growth of five cover crop species exposed to A. hybridus extracts, and to dried or fresh materials in soil. A germination index was calculated, and the dry weight of plant organs were measured to quantify responses to treatments. All species had reduced germination (≤29%) in 100% extract. Trifolium pratense had significant root weight reductions in extract (52%) and dried (72%) treatments, whereas shoot weight only decreased (48%) in dried treatment. Medicago sativa shoot weight decreased (52%) in 20g fresh treatment, while root weight decreased (62%) in dried treatment. Shoot weight of Raphanus sativus increased (32%) at mid-extract concentrations, while root weight increased (33%) only with dried treatment; however, both its shoot and root weight decreased (>40%) in fresh treatment. Only the shoot weight of Lolium multiflorum increased (41% in 75% extract and 55% in dried treatment). Both Cichorium intybus shoot and root weights decreased (~50%) in fresh treatment. Crop responses to A. hybridus are complex, and material and species-dependant. Further testing in the field may provide a more comprehensive understanding of how to improve the management of A. hybridus.
Highlights
Crops and weeds interact with one another in a variety of ways and can be classified as either competitive, facilitative or neutral [1,2]
The objective of this study was to determine if locally-sourced A. hybridus extracts had the potential to influence the germination and growth characteristics of five commonly-used cover crop species: common chicory (Cichorium intybus L.), oilseed radish (Raphanus sativus L. variety Nitro), red clover (Trifolium pratense L.), alfalfa (Medicago sativa L.), and annual ryegrass (Lolium multiflorum Lam.) These species were selected as they are commonly used in vineyards of the Niagara region, Canada
We assessed the germination potential and plant growth, reflected by weight, of selected cover crop species exposed to various concentrations of A. hybridus tea solution and dried ground or fresh plant materials incorporated into the soil
Summary
Crops and weeds interact with one another in a variety of ways and can be classified as either competitive (e.g., for water, nutrients or light), facilitative (e.g., enhancement of soil nutrient availability resulting from nitrogen symbiotic fixation capacity of legumes) or neutral (i.e., no obvious interactions) [1,2]. Cover crop species are often grown for their ability to inhibit weed establishment without any adverse effects on the main crop [6,7]. Farmers may choose to introduce cover crops alongside, or in rotation with, the main crop to reduce their use of herbicides [8]. The effectiveness of these cover crops will depend on their capacity to overcome weed competition. Cover crops are often used in perennial crop systems such as vineyards. They have been used for various reasons, such as protecting the soil against erosion, improving soil fertility and water holding capacity, and reducing weed pressure [8,9]
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