Green Lawns: Are they worth the cost?
Hypoxic dead zones. Where the Mississippi River drains into the Gulf of Mexico, there exists a zone the size of New Jersey so polluted with the run-off from middle-america that no plants or animals can live there. Much of this pollution comes from the over-treatment of urban lawns. Is it really worth it?
Collateral damage. Herbicides affect more than just the plants on which you use them. Please don't spray them if you live near an apiary, or if there are a lot of flowering plants in your area. Herbicides, fungicides, and other pesticides are likely culprits in the ongoing bee depopulation disaster known as Colony Collapse Disorder. The thought of a world without bees is a very scary one indeed.
Natural Alternatives to Herbicides
Laying down plastic. A great way to get rid of grass or other weedy plants is to lay down a layer of plastic over the targeted area during the summer months. The heat created by the sun becomes trapped under the plastic, creating a greenhouse effect, which will kill the plant within a couple of weeks, depending on weather conditions. Be sure to look for sharp stems or rocks that may pierce the plastic, and if you live in an area with any wind, be sure to stake the edges or weigh them down with dirt or rocks. Mulching with grass clippings and a layer of cardboard or newspaper will also work in a pinch but not as effectively due to their biodegradability.
Organic herbicides. There are many natural products which will kill grass but not be as harmful to plants and animals around you. As mentioned above, urine will kill grass spots pretty effectively through over-fertilization. But it is spotty, and perhaps unattractive. Some other options include, distilled white vinegar, which is acidic enough to kill a plant by changing its pH levels, and corn gluten, which has been shown to prevent grass seeds from sprouting. This means that it can be applied to an area to prevent the re-emergence of grass in the future.
Alternative ground cover. A good—albeit slow—method for getting rid of grass is to plant other ground covering plants in with the grass and eventually those other plants will win. You just have to be careful about what you plant because some ground cover plants are even more pervasive than grass. Clover is a good option, as it produces a nice flowering crop for pollinating insects and is also aesthetically pleasing. Some other options that are less desirable would be Creeping Charlie (Glechoma hederacea), Snow in the Mountain (Aegopodium podagraria variegata), and common mallow (Malva neglecta). Of course, the best option, for many reasons, would be a commercially available prairie wildflower and grass mix.
Hire a ruminant. If you are just looking to keep a pasture area from growing wild, it is pretty hard to beat a herd of goats, sheep, or a bunch of hungry cattle. This obviously isn't realistic for many of you. But it is all the rage these days. Not only will they keep tall grasses at bay, but they will make short work of brush and thistles. It can also be argued that they are cathartic to have around and plain old fun to watch.