Throughout history, man has used manures, fallen leaves, grass clippings, wood chips and many other natural materials for mulch in the garden. There are so many more types of mulch than this article can elaborate on, so we will cover the types that may be most readily available. The mulch mobile is filled and ready to head out to the vegetable garden.
It is a well-known benefit that mulches help to retain even moisture in the soil, so that plants are not going through dry periods between watering. Mulches are also known for their ability to slow down weed growth and for those weeds that do make it through the mulch; they are easier to remove from the garden soil. Here's a photo of pine shavings used as a mulch on newly planted Blackberry plants.
Although living mulches are also known as cover crops, green manures or catch crops, these will not be discussed in this article. Plastic mats and rolls, rocks and ground up rubber tires, and similar mulching products, will also not be discussed here. This article will cover mulches that you can turn back into the soil after use.
Mulches make the garden look clean and neat; they keep soil off of garden vegetables that grow on or near the ground. Once the mulch has done its job for the season, they are simply turned into the ground, and add to the soils tilth and structure. In addition, when mulches become part of the soil, they add nutrient and microbial activity to the soil as they break down.
Mulches can break down very rapidly, or they can stay in the same spot for years, returning to the soil very slowly. An example of mulch that breaks down quickly is finished compost. Compost that has been allowed to complete the composting process, cool down to acceptable and usable temperatures, and be run through a fine mesh screen can be used as mulch at about three inches thick. It will break down within one season. This application may also be considered a side dressing for the benefit of nutrient in the compost.
On the other hand, mulch that lasts for an extended period of time in the vegetable garden might be something like wood chips. Unless the chips are shredded down into very small particles, they will take more than one season to break down. The bulkier the material you use, typically the longer it will take to return to the soil. Leaves will break down fairly quickly; however, shredded leaves will break down faster.
There are other considerations when using different types of mulch in the garden. If you use fresh manures as mulch directly under the plants, you are likely to burn your plants. Some manure is better left to dry out or to be composted prior to use. Chicken manure is considered hot and will certainly do damage to your plants, so compost it first. Rabbit manure is considered a "cold" manure and can be added directly to your plantings.
Horse and cow manure may contain pathogens, so they should be left to dry out for a season, or composted to kill off these troublemakers. You can also turn manures under in the garden in the fall and let them decompose all winter long.
Here are some quick notes and things to consider with the following mulches:
It’s best to compost it before use, or to let it rot. Cow manure may contain a lot of weed seeds, so I always compost first. Horse manure may contain microscopic worms and other pathogens, so I compost first or turn under in the fall when I’m not growing anything. If you do decide to use horse manure as mulch during the growing season, use no more than 3 inches thick, as it will mat once it is wet, and will not allow water to penetrate very well.
Manures are also known for being the cause of E.coli. All vegetables harvested from areas in the garden that used fresh, or uncomposted manures must be washed well prior to being eaten. When you work with any kind of manure, you should always wash your hands well before coming in from the garden.
Straw is excellent mulch, and does a great job at retaining moisture and keeping the garden area relatively free from weed growth. This material is very high in carbon, so it may take away nutrient from the soil as it breaks down. I usually spread a high nitrogen fertilizer prior to placing straw mulch. Once the season has ended, straw mulch can be turned under and left to decompose through the winter months. You can usually find straw at your local feed store for a low enough prices that justify its use. Here's my YouTube video on using straw mulch
Grass clippings are full of nitrogen and break down quickly. I never use more than three inches of this kind of mulch, as it will mat down and may eventually begin to smell bad. Use only cool season grasses as mulch. If you use Bermuda, or any other trailing type of grass clippings, you are bound to grow a nice lawn in your vegetable garden, and you don’t want that. I try my best to keep any kind of grass clippings out of the garden and out of the compost; unless I’m certain that they are a cool season type like fescue or rye grass.
Wood chips are also great as a mulch to use when you need one to keep the weeds to a much reduced level. They are also very high in carbon, and take a long time to decompose. Fertilize prior to applying this mulch around your fruit trees. I’ve connected with multiple sources that provide me with an endless supply of wood chips for free.
I try to keep a pile in the back yard all year long, so I have them on hand when I need them. I turn them under in new garden plots that I won’t actually be using to grow vegetables for a year or so, to add tilth to the soil. When mixed with horse manure and turned under, they break down very well over the winter months.
Leaves also make excellent mulch. Most leaves can be used directly as mulch in the garden. Avoid using sycamore leaves unless they are shredded and composted first. Shredding leaves first avoids any matting of leaves and also helps to avoid any diseases brought on by matted leaves. Eucalyptus or Oleander leaves are also not good mulch. Do not use these in your vegetable garden.
Although I’ve used pine needles in the past, they just are not available to me here in the Dallas, Texas area. I would typically use them in the landscape rather than the vegetable garden. I would compost them before mixing that finished compost in my garden. Pine needles are known for adding acid to the soil, but you’d have to add the needles for many years to have even a small increase in the amount of acid in the soil, so just add them to your compost pile when they are available.
There are so many more types of mulches available to you in your area. Give them a try and see what works best for you. Remember, just like it is important to use a variety of plant matter and manures in your compost heap, it is equally important to use a variety of mulches in the garden, You will be providing a variety of nutrient to the soil when you turn the mulch under.