Take a look at this resource for managing weeds ecologically from Extension. Included in the article is a summary of organic weed management tools, planning steps, preventive steps, control steps and enhancing your system
Ecological weed management begins with careful planning of the cropping system to minimize weed problems, and seeks to utilize biological and ecological processes in the field and throughout the farm ecosystem to give crops the advantage over weeds. In addition, mechanical and other control measures are usually needed to protect organic crops from the adverse effects of weeds. This is particularly true in vegetables and other annual crops, for which production practices keep natural plant succession at its earliest stages, thereby eliciting the emergence of pioneer plants that can become agricultural weeds.
While tillage and cultivation can degrade soil quality and increase the risk of erosion losses, many other organic weed management tools (Table 1) are more soil-friendly. For example, a diversified rotation of vigorous cash crops and cover crops can enhance soil organic matter, tilth, and fertility, provided that a sufficient quantity and diversity of residues are returned to the soil to feed the soil life. Grazing livestock after a production crop to remove weeds or interdict weed seed set can add fertility in the form of manure, though intensive grazing can also compact the soil. In the interest of food safety, care must be taken to avoid direct contact of fresh manure with vegetables and other food crop. Mowing and flame weeding (if properly done to avoid excessive heating of the soil itself) are much easier on soil structure than cultivation, and can be just as effective in certain stages of weed and crop development. Mowing or rolling a cover crop to form an in situ mulch can enhance the soil benefits of the cover crop, compared to tilling it in, and can effectively suppress many annual weeds. Other organic mulches, such as straw and chipped brush, add organic matter, whereas synthetic clear or colored plastic films and weed barrier fabrics do not. All mulches are very effective in preventing soil erosion.