Using wood chips mulch in a vegetable garden: impacts on soil & plants

Wood chips have many practical applications in almost every sphere of our life. Probably the most popular of their uses is in the vegetable garden. There are many misconceptions about the benefits of using wood chips as mulch in the vegetable garden. In this article, we will try to deal with some of them and will try to disprove them.

Wood chips mulch increases the acidity of the soil

That is not 100% true in all of the cases. In fact, there are woodchips from trees which increase the acidity of the soil and others which make it more alkaline. An interesting fact is that most of the mulches make the soil less acidic and only the mulch from a few plants has the opposite effect. Amongst them are the mulches from pine (bark and needles) and oak (leaves). Some sources even claim that using wood chips as a mulch will not affect in any way the acidity of the soil below.

Wood chips rob soil of nitrogen

It is a true fact that a nitrogen deficiency appears in the layer where the mulch and the soil meet. That is why gardeners should plant below this level in order to be able to avoid it. The best option here is to use some kind of high nitrogen amendment, such as blood meal just below the mulch layer.Experts advise also to use wood chips which include leaves. That is because leaves are a great source of nitrogen.

Wood chip mulch requires the use of a lot of composted manure to balance C: N ratio

Wood chips contain a high amount of carbon. That is why in order to be able to offset the high carbon ratio in wood chips you should use considerable quantities of composted manure. Vegetables require the carbon-nitrogen ratio to be 30:1 or lower. Fresh wood chips contain 3 times that much carbon! That is why should use a compost to stabilize that ratio. A thick layer of compost will not only increase the growth of your vegetables but will also suppress the growth of weeds which can have a devastating effect on all of the plants.
4. Long-term use of wood chip mulch may increase the fungal dominance in your soil food web
Annual vegetables develop and grow well in soil dominated by bacteria. That is why, if you apply wood chip mulch the vegetables will grow really well during the first few years, but after that, when the fungal dominance is established, you will begin to see a decline. If you find yourself in such conundrum there is one simple solution-scraping the uncomposted wood mulch completely and tilling the soil once again. That will re-establish the bacterial dominance in the soil and make it fertile once again.

Some trees are poisonous to other plants

There is a specific word for the negative effect which some trees can have on other plants-allelopathy.The exact definition of allelopathy is:”the suppression of growth of one plant species by the other thanks to the release of toxic substances”. This means that you should be a 100% sure what trees are in your wood mulch, otherwise you can inadvertently kill all of your crops!

A tree with a strong allelopathic effect is the black walnut. That is why sawdust mulch from the walnut tree is not suggested to be used for plants sensitive to juglone, such as blueberry or other. However, composting made of bark from a walnut tree can provide mulch for a period of six months even for plants sensitive to juglone.Juglone can have a negative effect also on blackberry, blueberry, apple, cabbage, peppers, tomatoes, eggplant, potatoes, and certain cole crops.

Other trees which have a strong allelopathic effect on trees include hickory, pine, sassafras, and oak.

Wood chips for mulch can inhibit seed germination

When wood chips become heated and begin decomposing they can release volatile organic substances that can inhibit plant growth. That statement is partly true. Some seeds, especially smaller ones planted in the layer between the mulch and the soil do not germinate at all. Despite all that, this can have a positive effect on plants because the seeds of the weeds do not germinate too. Some crops, such as onions, carrots, and squash do not perform very well. That is why they should be planted in the soil below rather than in the mulch.

Wood chips being used as a mushroom cultivation

Another application for mulch made from wood chips is to use them for mushroom cultivation. The simplest way you can do this is to obtain some seeds which are inoculated with mushroom spores. The next thing which you should do is to plant these spores on pre-soaked wood chips placed in a shady spot. Growing mushrooms in your garden can have many substantial benefits including adding biodiversity, food resilience for you with a new edible crop, and even bioremediation or cleaning the soil and water in your area.

Wrap up

As we saw from the above article wood chips used for mulch can have many benefits for the plants grown in your garden. They can add the necessary nutrients to the soil, decrease soil erosion, provide moisture retention and even suppress weeds. Nevertheless, they can be a useful option in terms of energy efficiency and environmental protection- if you can obtain them as a byproduct of a different process. Wood chips can be made with a home use wood chipper from tree branches. If you are pruning or trimming a tree you should have plenty of branches that you can turn into chips. If you need to buy a wood chipper I suggest that you read my review of the best wood chipper shredders for home use. If you are interested to read more about wood chips check out my article about what to do with wood chips from a wood chipper. I hope that you found this article interesting and informative.

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