How To Get Rid Of Weed Seeds In Soil

Yard and Garden News Landscape fabric also works well to suppress weeds. It is most appropriate for transplanted vegetables, since holes can be cut into it to plant seedlings. Mulch can be One method of weed control is to remove weed seeds in the fallow, stubble and pre-sowing phase. This can be achieved by encouraging the germination of weed seeds and then subsequently killing seedlings or destroying seeds and reducing seed viability. This section covers the different methods used to deplete weeds.

Yard and Garden News

Landscape fabric also works well to suppress weeds. It is most appropriate for transplanted vegetables, since holes can be cut into it to plant seedlings.

Mulch can be applied at any time, but it is generally a good idea to wait until late spring, once the soil has warmed. Vegetables need warm soil to grow, and applying mulch too early will keep the soil cool for longer into the spring, potentially slowing the growth of vegetables.

In particularly wet years, mulching too early can also create habitat for slugs that chew on vegetable leaves.

2: Throw away or burn mature weeds – Do not compost them.
If left to grow, one common lambsquarter plant can produce over 70,000 seeds on average. Photo: Annie Klodd

The best way to control weeds is to not have them in the first place. Fortunately, there are ways we can help reduce the amount of weed seeds that get into our garden’s soil.

The most important tip is to never leave mature weeds in the garden, otherwise they will deposit their seeds into the garden soil and lead to more weeds in the future. Did you know. weed seeds survive in the soil for several years, and some common species can produce hundreds of thousands of seeds per plant?!

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That’s why you should always remove weeds before they are mature enough to flower and produce seeds. But if weeds do grow to maturity, remove them as soon as possible and either dispose of them or burn them – do not leave them in or near the garden, and do not put weeds in the compost pile if they have flowered or have seeds on them.

Composting can only kill weed seeds if all parts of the pile reach at least 140 degrees F for an extended period of time. While some commercial farms and composting facilities achieve these temperatures in large piles that are turned regularly, ideal conditions are challenging to achieve in a home garden setting.

3: Use the hoe and tiller wisely!
Tilling a garden on May 8, 2018, about three weeks before planting warm-season vegetables.
Photo: Annie Klodd

Have you ever noticed big flushes of new weeds after you till your garden soil in the spring? When we till, hoe or rake the soil, that disturbance does uproot existing weeds, but it can also lead to new weeds. This is because tilling stimulates buried weed seeds to grow by exposing them to the sunlight and warm temperatures that they need to thrive.

Using tillage strategically, and understanding a bit about how weeds grow, can help reduce weed problems before even planting the vegetable garden in the spring. A tillage technique called a “stale seedbed” aims to do just that.

Try the stale seedbed technique

In the stale seedbed technique, the soil is tilled or hoed just once, about 2-4 weeks before planting. This purposefully forces weed seeds to emerge early, before the vegetables are planted. The soil is then left undisturbed until it is time to plant.

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Right before vegetable planting, the surface of the soil is raked or hoed again to kill the emerged weeds. After planting, try not to disturb the soil again, in order to discourage new weeds from coming up. A mulch or landscape fabric can be laid down at this time in order to suppress further weed seeds from emerging.

It helps you begin the season with a head start on the weeds, and what gardener doesn’t like that?!

Crop weeds: reduce weed seed numbers in the soil

Please note: This content may be out of date and is currently under review.

One method of weed control is to remove weed seeds in the fallow, stubble and pre-sowing phase. This can be achieved by encouraging the germination of weed seeds and then subsequently killing seedlings or destroying seeds and reducing seed viability. This section covers the different methods used to deplete weeds.

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Different weed control methods

Burning crop residues

Burning can reduce the surface seed banks of many weeds. All crop residues (canola, wheat, lupin and others) can produce a sufficiently heated burn to kill weed seeds. A narrow windrow will burn at a higher temperature and improve weed seed kill.

Encouraging insect predation of seed

Weed seeds provide a major component of many insect diets (predominantly ants). There are methods to increase populations of insects over the summer/autumn fallow and therefore increase insect consumption of seeds.

Inversion ploughing

Fully inverting the soil will ensure that weed seeds that were on or just below the soil surface are placed at a depth from which they cannot germinate. This can be practiced every 8-10 years, with conservation tillage used in the intervening years. In Western Australia, annual ryegrass seeds failed to establish and eventually died when soil was fully inverted to a depth of greater than 20 centimetres (cm) using a specialist mouldboard plough fitted with skimmers. This single soil inversion event reduced annual ryegrass numbers by over 95% at Katanning and Beverley for a period of two years.

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Autumn tickle

This does not destroy seeds but rather buries them to a depth of 1-2cm, enhancing seed germination by increasing contact with soil moisture. This encourages weed seeds to germinate earlier. A delay between the tickle and seeding is necessary to give an opportunity for the weeds to germinate and then be killed using a knockdown herbicide. The delay to seeding will result in a yield penalty for some crops.

Delaying sowing

This allows greater germination of weeds in particularly weedy paddocks, which can then be killed using a knockdown herbicide or cultivation prior to crop sowing. The longer the delay in sowing, the more weeds germinate and the higher the kill. However, a yield penalty is experienced when sowing is delayed.