Last week I discussed how mulches are used on our landscape beds. Vegetable gardens can also benefit from a good mulching now and then. Often, our goals will determine the type of material used.
In spring, we can speed up the season by using plastic mulches. They act like a greenhouse to warm the soil. Clear plastic warms better than black but it also allows more weeds to grow. A good thing about plastic mulches is that they hold in moisture. A problem is that they don’t allow it to enter in the first place.
Cloth mulches can help in this area. I prefer heavy-duty geotextile cloth. I think it’s worth the investment. This material suppresses weeds and eliminates copious handwork. In a garden situation, it’s usually necessary to remove it after a few years so the soil can be conditioned. Soil compaction between rows eventually becomes a problem.
Organic mulches will eventually turn into compost. Almost any material can be used. Leaves and grass clippings are the most common. When they decompose or weeds begin to be a problem, they can be tilled into the soil to increase organic matter and general soil tilth.
An important thing to remember is not to apply too much at a time. A two-inch layer is ideal. More than that can cause them to mat down and shed water. Also, in the case of dry leaves, they often have a wide carbon to nitrogen ration and additional nitrogen might have to be added. This can be accomplished by adding bagged fertilizer or nitrogen from an organic source like manure.
Sawdust and wood shavings are often used on strawberries. They’re not quite as popular for general vegetable garden use. Plants often become nitrogen deficient during the decomposition process and additional nitrogen must be added to correct it.
Pine straw is another possibility. People are often concerned about lowering the pH of the soil too much, but I think that is overrated. That concern can be overcome by adding a little lime anyway. A little more calcium might just help control blossom end rot on those tomatoes too.
Straw is another material people sometimes use. Like dried leaves and wood shavings, it has a wide carbon to nitrogen ratio. Another problem with straw is that it will contain lots of seed. Sometimes it will look like you planted your garden in wheat. This is not entirely bad. It might be unsightly, but the wheat will not be there forever
Newspaper is another popular organic mulch. Placing it on the garden is a good way to get rid of it. It will eventually decompose and add to the soil. In the meantime, the newspaper will help suppress weeds. The biggest problem I have with it is that it usually dries up and blows everywhere.
Whether you choose to mulch or clean till your garden is a personal decision. Adding organic matter is always a good thing, but some folks prefer to incorporate it immediately and not leave the material on the surface. Enjoy your garden either way.
Ted Manzer teaches agriculture at Northeastern High School.