Mulch on a vegetable garden is absolutely critical to the success of the harvest. Mulch is not an option on the vegetable garden. It is critical because it is food for the soil food web.
For 50 years gardening books have reported the function of mulch:
1. It prevents weeds from growing in the garden
2. It slows down the evaporation of water from the soil
3. It cools the garden soil in the heat of summer
However, while mulch does those three things, there are two more functions not mentioned in the books that are absolutely critical:
4. Mulch creates a habitat for the key beneficial insects in a garden including ants, spiders, and ground beetles. They will contol over 50% of the pest insects entering the garden. See discussion.
5. MOST IMPORTANT – MULCH IS FOOD FOR THE SOIL FOOD WEB
What Material Can I Use For Mulch?
There are really only two options for organic mulch for the vegetable garden:
1. If you have trees then you have leaves. Chopped leaves makes an excellent mulch and they are free. The leaves need to be chopped by either a mulching mower or a leaf shredder to give the habitat that is needed and be bite sized for earthworms.
2. If you have no leaves, then straw is the best material. It is relatively inexpensive and last most of the season. In both cases you will likely refresh the mulch in the spring at the beginning of the season and then in the fall.
You need to have 3 to 4 inches of organic mulch on the veggie patch 365 days a year. When it gets down to 2 inches, it needs to be amended.
What Is The Soil Food Web and Why Do I Care?
A healthy soil with over 5% organic matter will have billions and billions of visible and microscopic creatures in a completely integrated community. Just one tablespoon of healthy soil will contain over a billion microbes. The visible members in the soil are earthworms, millipedes, centipedes, sowbugs, earwigs, springtails and many more. The little microscopic guys include billions of beneficial bacteria, fungi, protozoa and again many others.
The creatures in the soil food web will turn organic matter in the soil into liquid nutrients that are in a form acceptable as food by all plants in that soil. In a soil with 5% organic matter you really don’t have to add any fertilizer; ever.
The organic mulch is lunch. It is the essential food to keep the soil food web population high and healthy. No mulch, the soil food web diminishes to a level where it is no help to the plants and you have to fertilize often.
So it is a no-brainer for us. Organic mulch leads to success in the harvest. It does not make any sense not to have that mulch over the entire garden 365 days a year.
Here is a drawing showing the soil food web.