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weed suppression seeds

Bale direct collects all the crop residue directly from the combine and compacts it into large bales suitable for sale.

Impact mills run the chaff through a mill that pulverizes (destroys) the weed seed, which is then spread across the fields. This technology is usually considered the ultimate in HWSC.

At harvest time, weeds that have escaped season long management often have mature seed still attached to the parent plants. These weed seeds can enter the combine along with the cash crop and exit the back of the combine in the chaff portion (small plant pieces and weed seeds), separate from be spread across the field as well as from one field to another. It seems a waste to spend all year spraying weeds with expensive herbicides only to reward the survivors at harvest by spreading their weed seeds out for next year.

Learn More About Each System in This Research Report

2. Get maximum weed seed into the header.

Chaff carts are a tow-behind unit on the combine that collects the weed seed-laden chaff, which can then be placed into piles that are later either grazed by livestock, burnt, or both and sown through the following season. Chaff carts are often chosen for use on mixed cropping and livestock farms in Australia as the chaff is an excellent livestock feed; however, spreading manure back onto fields can allow for further seed spread.

Over 80% weed control for species that retain seed at harvest

If you are considering adding harvest weed seed control (HWSC) to your weed control program there are excellent resources on the WeedSmart website to help guide you through the initial decisions and the implementation of this important weed control tool.

Sow cool season crops like oats, field peas, bell beans, and forage radish in early spring when cool moist soil conditions favor rapid growth. Plant winter annuals like cereal rye (Fig. 2), wheat, winter barley, vetches, crimson clover, and Austrian winter peas at the end of summer or in early fall, giving them time to put on about 4–6 inches of growth before winter freezes render them dormant. Avoid planting any cool-weather cover crops at a time that will expose them to summer heat (daily highs of 85°F or more) before they approach full height. Heat retards their growth and lets summer annual weeds break through.

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic’s articles on organic certification.

Choose the Right Cover Crop for the Climate and Season

On lower-fertility soils, be sure to provide organic sources of nitrogen, phosphorus, and potassium (NPK) for heavy-feeding cover crops like sorghum, sorghum–sudangrass, radish, and wheat. Well-fed sorghum–sudangrass can reach a height of nine feet in 75 days and smother weeds, whereas underfed sorghum–sudangrass is thin, yellowish, and weed-infested at the same age. Buckwheat, pearl, and foxtail millets are somewhat more tolerant to lower soil fertility levels, while cowpea, sunnhemp, cereal rye, and hairy vetch can be considerably more so. However, when soil fertility is low, all cover crops respond to compost and other slow-release nutrient sources with increased vigor, higher biomass, and better weed suppression.

Figure 6. These young cover crops of sorghum–sudangrass and lablab bean (a tropical legume suitable for warm humid climates in the southeastern US) are sufficiently dense and uniform to compete effectively against the few weeds emerging with them. This stand should be allowed to grow until the grass begins to head in order to derive the maximum benefit. Mowing sorghum–sudangrass back to a stubble height of about one foot and letting it regrow has been reported to stimulate additional rooting, which could further enhance its weed suppressive effects. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

It may be appropriate to spread aged manure, compost, and/or slow-release organic fertilizer before planting a cover crop. Make sure that the materials to be used do not carry a lot of weed seeds. Feeding a cover crop is an excellent way to use manure that has not been hot-composted in certified organic operations, which require a 120-day interval between manure application and vegetable harvest. The cover crop takes up the nutrients, and both the cover crop and the amendments contribute to soil humus and nutrient levels at the time of the next vegetable planting.