There are alternatives to using herbicides, pesticides, and fertilizers on the country's nearly 30 million acres of lawn. Along the way to becoming chemical-free, you may even find a virtue or two in some common weeds. Perennial rye grass is the best competition for crabgrass. Fertilizing is key and must be done in the spring and in the fall. Crabgrass thrives in compacted lawns.
Aeration can help.
A mixture of 1 pint of hydrogen peroxide, diluted to 3 percent, per 100 square feet of lawn can help eradicate the pesky plant. Corn gluten meal, a relatively new and increasingly popular natural herbicide, appears to be successful at preventing crabgrass and other common weeds. A by-product of milling corn, it is completely benign. Some companies sell a pelletized form containing potash and nitrogen, but you may have to search a bit or ask your retailers to stock it. You can eat their young leaves in salads, and in fact, they were brought to this land as an exotic green.