Crabgrass is an annual grass. Comes up from seeds each year. You can reduce it by tilling it down before it seeds, but seeds will remain for several years. The key is to keep it from seeding. Roundup up will kill the live plants, but you have to prepare the seedbed for a cover crop anyway, so it seems an extra expense for little gain. I use rye as a cover crop. Most seed and and feed stores carry it. Widely used for planting deer plots. There are other winter hardy plants that can be used. In a small plot sometimes I just plant turnips, mustard, and kale.

I don't recommend Roundup, you don't need it. As mentioned above, look in the phone book for farm supply stores. Or make a list of what crops you want and order directly from seed companies.

The following is a copy of a post I recently responded to, note my main suggestion:

The key to getting rid of weeds and keeping an area weed free is planning far enough ahead and constant maintenance.

Weed eating is a futile effort unless your taking out the roots as well. So long as the roots are still in the ground, most of your weeds will continue to come back. You need to completely eliminate the entire plant: top and bottom.

Depending on what "weeds" were in your soil that you tilled, you most likely brought up dormant weed seeds that were too deep to sprout and broke up stems (crab grass for instance) into smaller pieces where the nodes still sprouted.

Here is my suggestion to you due to the size of your area:
If tilling is the chosen method, then do so at least six weeks in advance, and preferably months in advance in order for the soil tilth to build back again as well as for dormant seeds to sprout so you can skim them to kill them as they come up. Do this a few times for a couple of weeks until they've subsided, then you're ready to plant.

Next you need to mulch and mulch well (2-3 inches). This will prevent further sprouting of weeds and prevent migrating wind born seeds from taking root in your soil. If you plant vegetable seeds, you can mulch with a thin layer of shredded leaves or grass clippings or compost or straw, etc. When the seedlings get 3-4 inches tall you can mulch at a greater thickness and more as they get larger.

If you had that many ants, your soil must have been too dry. Mulch will help keep your soil moist and the soil temperature stable.

If you want to go the newspaper route, try Freecycle.org and ask for newspaper. You might be pleasantly surprised. There's probably someone out there (like me) with plenty of newspaper to share, especially if it's going to good use and getting recycled. You can also call your local newspaper, tell them what you need it for and ask if they have any discards.

You need to do layers of 8-12 damp (soak them in a bucket of water first) sheet, then cover with soil. If you don't it will dry and fly away. But if you can cover with soil, or mulch, it would work. You can also try cardboard. Call local businesses for both. You can also try black plastic mulch, but it won't add organic matter to your soil.

The issue with straw are seeds which might sprout and cause problems. It works great, just make sure you know what you're getting:

When using hay or straw, you need to know your source and exactly what is in the bales.

Hay and Straw Glossary
A popular organic mulch, hay is commonly used to protect soil and plants from the elements, to line pathways, and to address various needs in the garden. What many people don't realize, however, is that various products are often labeled as "hay" at garden centers, but there are many different types of hay and straw that are commonly sold in bales. While they are easily confused, it's important for gardeners to become familiar with the differences.

Salt hay
Salt hay, or Spartina patens, is a grassy plant that grows in salt marshes and wetlands. Martha has long used salt hay in her gardens. It is useful for keeping weeds from growing in paths, preventing runoff, and keeping soil from turning into mud whenever it rains or the garden is watered. A layer of salt hay will keep soil moist and encourage worms to come to the surface, which will help to aerate the soil. It also makes an attractive path to walk on between garden rows. Salt hay is an ideal all-purpose mulch because its seeds won't grow away from salt water'so it won't germinate in your garden.

Golden straw
What is commonly termed "Golden straw" is either oat straw, Avena, or wheat straw, Triticum. This straw is a by-product of the process of separating oat or wheat seeds from their stalks. Golden straw is often used as bedding in horse stalls; because there are no seeds, the horses won't eat it. This straw spreads nicely, and the lack of seeds means there is no risk of it germinating in your garden. It can be used in the same way as salt hay.

Wheat straw
An excellent choice for straw for use in the vegetable garden. Lay down six inches in height in the fall then direct sow seeds in the spring. No need to dig. There will be a handful of weak sprouts from seeds, just pull them out.

Feed hay
Just as its name implies, feed hay is used to feed livestock. Though inexpensive and plentiful, it is not a good choice for use in gardens because it is full of seeds. The main ingredient of feed hay is alfalfa, Medicago sativa. It also frequently contains flowers and seeds from many other plants and weeds such as clover and golden rod. These seeds are likely to germinate, resulting in a garden full of weeds rather than flowers and vegetables.

Soil Solarization is another technique you can use, using clear 6 mil plastic. It has been around for a long time. It's effective for those who have patience and can plan ahead. A drawback is that it kills beneficial organisms and bacteria in the soil.

What I do is lay roof shingles over any area where I want to create a bed. Within two weeks vegetation underneath is weak and pretty close to dead. I wait until the soil is crumbly underneath, sink my spade in and start hand sifting and pulling out everything then I crumble it back in the spot along with compost so it's light and airy and never walk on it again. Then I'll mulch with leaves and/or grass clippings. Usually the latter.

I don't do huge areas of space at a time. Literally just lay them on top of the grass and overlap them a bit so light doesn't get thru. After a couple of weeks and after a rain check to see if the soil is "friable" (soil crumbles in your hands). Length of time after a rain will depend on whether your soil is sandy, clay, etc. For me it can be 2-3 days in certain parts of the yard, 1 day in another area of the yard. When you lift the shingles, you'll see there is little to no grass and what you can see is yellow or white. Sink a spade in and lift up, then just get in there with your hands and fingers and take a chunk and pull out the roots. This works fabulously with bermuda grass because the main runner stem is in tact but the roots have died off so all you have to do is follow the runners. Sometimes they're 4 feet long. But they're soooo much easier to get out! Much less work than tilling and sifting.

Then crumble the soil lightly back into the spot with your fingers. As you crumble take out out any weed matter and into the compost pile they go. This is the best time to incorporate compost or any other soil amendments. Now don't walk on the area or you'll compact the soil.

I'll take out large rocks as well since we grow rocks around here. I've responded to "Wanted: Rocks" on freecycle.org a couple of times so now they're gone and have found use to fill holes under fences so dogs don't escape.

The problem with tilling bermuda grass is that when you do that, you create a lot of little pieces that are not easy to find and get out without a sifter. If one tiny piece with a node get's left behind, it'll take root and take off and you have the same problem all over again.

Overview of Cover Crops and Green Manures

Here is a link that might be useful: Weed Control

The wheat straw I've been getting is seedy lately...possibly because wheat farmers are getting more for bales of straw as animal feed than they would from the actual wheat?

But at any rate, I've found wheat grass to be an excellent weed blocker. In November or so I put down an inch of the excellent pig manure compost I get from some friends and then about six inches of wheat straw. Come spring I have a crop of wheat, but it pulls out in clumps and underneath there's rich, moist, wormy soil. The clumps of wheat grass go over the cardboard-lined walkways or into the compost heap.

Ed