Got this information from another group via email, so don’t know what the source of this information is:

Organic Landscaping in Planting Beds
“Weed control without chemicals” may conjure up unpleasant thoughts of getting down on your hands and knees in the yard on a hot day and pulling out stubborn weeds by hand. But weed control without chemicals needn’t be so primitive, so mindless. In the resources to which I provide links below, I discuss a variety of weed-control components to be used in planting beds. They should be used in conjunction with each other. Weed control without chemicals can be tough work, and I want you to work smarter, not harder. No need to revert to the Stone Age!

Weed Control Without Chemicals: Laying the Foundation
The first smart idea in a project of weed control without chemicals is to prepare the plot of ground in question. Just as in a construction project, laying a good foundation is of the utmost importance. In this context, by foundation” I mean the state of the ground where your plants will be growing. Implement these ideas before you plant, so that you’ll get off to a smooth start in your project of weed control without chemicals.
1. Killing Weeds Through Soil Solarization
Soil solarization is a preventive, organic method of killing weeds — before they even sprout! The advice below is meant for homeowners wishing to start out with a clean slate, re-landscaping a weed-filled patch of land in such a way as to reduce to a minimum the hassle of weed control in the future.
2. How to Lay Landscape Fabrics
For those in need of soil solarization (see above), installing landscape fabrics can be considered Step #2 in the project of weed control without chemicals. For those with less weedy properties, it’s Step #1. I promised you above that weed control without chemicals wouldn’t mean going back to the Stone Age, and landscape fabrics are a case in point. Landscape fabrics are a hi-tech ally in the battle against weeds.
3. Using Garden Mulch
As the final element in a good “foundation” for your bed of annuals, perennials or shrubs, you should apply garden mulch on top of the landscape fabric. Many skip right to mulching in the project of weed control without chemicals, but I do advise you to lay the landscape fabric first: it will lengthen the life of your garden mulch.

Q&A on Mulching Gardens
Weed Control Without Chemicals: Pre-Emergent and Post-Emergent Organic Herbicides
“Pre-emergent herbicides” is a fancy way of referring to herbicides that attack annual weedy plants at the source: their seeds. That is, they act to inhibit seed germination before the plants in question even have a chance to announce themselves to the world above! Corn gluten is a pre-emergent herbicide used for weed control without chemicals. Remember, corn gluten will inhibit the seed of “good” plants from germinating, too, so don’t use it in planting beds where you’re starting plants from seed.
By contrast, you apply “post-emergent herbicides” only after the antagonists have appeared on stage. For weed control without chemicals, try vinegar as a weed killer. Even plain old household vinegar is effective if you have only young weeds to deal with in your planting bed. It’s the acetic acid in vinegar that gives it its herbicidal abilities. The higher the percentage of acetic acid in the vinegar, the better. Vinegar used for culinary purposes is relatively low (5%) in acetic acid, but you can boil it down to increase its strength — a provision that is necessary
if you’ll be applying it on full-grown weeds. Alternatively, you can try to buy the super-strength vinegar in stores that cater to the agricultural community.
A word of warning, though, when using vinegar as an herbicide: apply it directly onto the weeds, since vinegar is a non-selective herbicide and will harm plants that are inadvertently exposed to it. For this reason, vinegar isn’t especially effective for battling lawn weeds: you’d almost inevitably end up with too much collateral damage to your grass. But vinegar is a fine organic alternative in planting beds, as long as you watch where you’re spraying!
Weed Control Without Chemicals: In Case You Still End Up Pulling Weeds
With landscape fabric and garden mulch in place, the bad news is that, even then, you may still get weeds. But the good news is that those weeds will be very easy to pull out. Pulling weeds embedded in mulch is not nearly as difficult as pulling weeds embedded in soil. Thus with a good “foundation,” you may not even feel the need to bother with the corn gluten and vinegar: 5 minutes of easy pulling here and there should get the job done.
One exception to this may arise: if the integrity of the landscape fabric has been compromised, weeds may strike down roots in the soil beneath, making them difficult to pull out. In this case, water the area in question beforehand. It’s usually easier to extricate weeds from moist soil than from dry soil.

Q. I have a question about controlling weeds in my garden. Unfortunately, I live 45 miles away from my garden, so it gets weedy very quickly. I was thinking about putting straw on top of the soil to keep the weeds down. Have any of you used this before? Any
other suggestions?
I need to keep it low maintenance because I sometimes go one to two weeks without weeding. I heard woods chips will rob the soil of nitrogen, so I’m avoiding that type of mulch. I’ve also heard about Preen, but I don’t want to use that near my vegetables.

Ans:

The down side of weeding is that there is about a 25 year supply of weed seeds in the soil so when you pull/ hoe the visible weeds away you are bringing fresh weed seeds into the grow zone. Preen is a Petro chemical seed inhibitor and it travels in the soil and hence into the water table. I would suggest Corn Gluten instead it provides the same activity as the Preen and as it wanes converts into a low grade nitrogen fertilizer. So that in combination with Oat straw should help you considerably. Do not use wheat or Alfalfa Straw as it contains weed seeds in it for it is made from a third or forth cutting and the seeds of the previous 2 or 3 cuttings along with the weed seeds are incorporated into the bales. They are designed for Bedding of livestock and shouldn’t be in the garden unless they have been composted at a high temp exceeding 180 degrees to kill the seeds.

Weed control is the botanical component of pest control, stopping weeds from reaching a mature stage of growth when they could be harmful to domesticated plants and livestock by physical and chemical methods. In order to reduce weed growth, many “weed control” strategies have been developed in order to contain the growth and spread of weeds.
The most basic is ploughing which cuts the roots of annual weeds. Today, chemical weed killers known as herbicides are widely used. Weeds can compete with productive crops or pasture, or convert productive land into unusable scrub. Weed are also often poisonous, distasteful, produce burrs, thorns or other damaging body parts or otherwise interfere with the use and management of desirable plants by contaminating harvests or excluding livestock.

In domestic gardens, methods of weed control include covering an area of ground with several layers of wet newspaper or one black plastic sheet for several weeks. In the case of using wet newspaper, the multiple layers prevent light from reaching all plants beneath, which kills them. Saturating the newspaper with water daily speeds the decomposition of the dead plants. Any weed seeds that start to sprout because of the water will also be deprived of sunlight, be killed, and decompose. After several weeks, all germinating weed seeds present in the ground should be dead. Then the newspaper can be removed and the ground can be planted. The decomposed plants will help fertilize the plants or seeds planted later.
In the case of using the black plastic sheet, the greenhouse effect is used to kill the plants beneath the sheet. A 5-10 cm layer of wood chip mulch on the ground will also prevent most weeds from sprouting. Also, gravel can be spread over the ground as an inorganic mulch. In agriculture, irrigation is sometimes used as a weed control measure such as in the case of paddy fields. Many people find that although the black plastic sheeting is extreemly effective at preventing the weeds in areas where it covers, in actual use it is difficult to achieve full coverage.

One technique employed by growers is the ‘stale seed bed’, which involves cultivating the soil, then leaving it for a week or so. When the initial flush of weeds has germinated, the grower will lightly hoe off before the desired crop is planted. However, even a freshly cleared bed will be susceptible to airborne seed from elsewhere, as well as seed brought in by passing animals which can carry them on their fur, or from freshly imported manure. The organic solution to the problem of spreading annual weeds lies in regular, properly timed weeding, preferably just before flowering (fortuitously, this is also the time at which they will be of the most value in the compost heap). This technique is also quite often used by farmers who let weeds germinate then return the soil before crop sowing.

Weed Control Without Chemicals: The organic way
Weed seeds exist in the soil of all gardens and can be spread by wind, water, animals and even by the soil amendments we use to help our gardens grow. Here are some ideas to consider for organic weed control:
- Improper watering, soil compaction, insect damage and disease all contribute to weed development. All of these conditions can be easily avoided by proper mulching.
- Without harming your crops, you can turn the weeds into the soil with a weeding hoe or any version of this time-tested tool.
- Use plastic or newspapers around plants to block weeds. It works well with warm weather-loving crops such as melons, pumpkins, eggplants and tomatoes. If using newspapers, then use a layer about ¼- inch thick and wet it down as soon as you lay it to stop it from blowing away. Then cover the newspaper with a layer of straw.
- Live mulches are gaining a lot of respect in the garden. The idea is simple; using a fast growing and short plant to cover the surface of the soil around the garden plants. Thyme is a perfect choice for this method.
- Corn gluten meal can be applied as a pre-emergent weed killer. It has been shown to inhibit the growth of dandelions, crabgrass and many other annual weeds.