Friday, February 27, 2015

Pros & Cons of Mulch

Mike asked via email why I use mulch. What are the benefits and the drawbacks? Mike felt that if mulch was so great, then everybody would be using it, right? But he noticed that farms never seem to use mulch and most magazine garden photos don't show mulch being used either.  Good observations! 

There are small farmers using mulch, but mostly on perennial crops. Annual crops are planted with farm equipment in mind, so mulch doesn't fit well into that picture. The exception is the use of plastic mulch....huge sheets of plastic laid down in rows through which a crop is planted. I have seen this technique used for corn, tomatoes, peppers, squash, and melons in certain situations. And a variation of this is the use of red colored mulch to enhance a tomato crop and reflective plastic (white or silver) to repel insects. Big farms can't use organic mulch simply because farming techniques can't accommodate it. Applying vast amounts of mulch would be difficult for most crops. Current systems of weed control, row cultivation, pest control, harvesting all prevent the use of mulch. Except for dust mulching. Depending upon soil type and weather, there are situations where a farmer will use shovel hoes or cultivators to produce a fine surface dust which acts as a moisture retaining mulch to some degree. In orchards, the use of mulch is more common than with annual crops. Here in Hawaii there are macnut farmers who return the harvest debris to the orchard in the form of mulch for under their trees. Others will maintain a layer of volcanic cinder under the trees as a mulch. I saw an orchard in NJ that was trying a fine pebble mulch under the trees. And another using coarse sand. But I can't say how effective those were. Since I saw zero weeds I have to assume that those farmers were also using a herbicide. 

So how about the pros and cons of mulch on my own homestead? Remember that I'm in Hawaii, so I don't need to be concerned with frozen or cold soil in the spring. Mulch in cold zones can keep cold soil from warming up in the spring. 

Pro--- when applied before weeds germinate (or while they are quite tiny), mulch effectively keeps weeds from taking over the garden.
Pro--- soil under a mulch retains moisture far, far better than that exposed to the sun and wind.
Pro--- soil temperature is cooler under a mulch. Most crops prefer cooler-than-air soil for their root zone. 
Pro--- soil micro-organisms thrive under a mulch. They are protected from the sun and wind, plus are exposed to less temperature and moisture fluctuations. 
Pro--- as the mulch decomposes, it supplies nutrients to soil microbes and worms. 
Pro--- worms thrive better under mulch
Pro--- soil structure is better under a mulch. Less apt to have drainage and compaction problems. Less apt to show hydrophobic characteristics. 
Pro-- good utilization of onsite organic material. 

Con--- creates a hiding place for pests. It's easier to miss noticing and finding destructive insects. Slugs like mulch. And so do mice. 
Con--- it is difficult to use on certain crops, especially those that are close to the ground, like radishes, leaf lettuce beds, micro greens, etc. 
Con--- if applied too thickly it can prevent rain from reaching the soil. Also along this same line, too thick mulch can cause the soil to stay too wet under certain circumstances. 
Con--- depending upon the material being used for the mulch, as the mulch decomposes it can rob the soil and crop of nitrogen. 
Con--- applied too thickly, certain materials can generate heat, thus killing or damaging the crop. 
Con--- certain mulch materials will significantly impact soil properties, thus affect not only nitrogen levels but also P, K, and pH. 
Con--- over proliferation of undesirable fungus and molds. Especially a concern when the mulch is matted and wet. It becomes slimy, slippery, and stinky. 
Con--- may contain weed seeds. Especially a problem when using old hay and straw. 
Con--- flammable (sand, cinder, etc not included.) Not a concern on my homestead, but it could be a real serious issue elsewhere. 
Con--- material brought in from other areas could bring pests and disease, plus could contain noxious chemicals. 

What do I use for mulch? Organic material. While cinder may look pretty around my fruit trees, I would have to use a herbicide like round-up for weed control.....or an awful lot of hoeing. No thank you to either.

1- Grass clippings are my number one mulching material. Easy for me to apply. I've learned how to effectively use them while avoiding problems. And I have year around access to them. 
2- Right there along side grass clippings is brush chippings. Chipped up brush and small tree branches make good mulch. 
3- Third is chopped up brush. This makes a coarse mulch. 
4- In the past I've used newspaper and cardboard with varying results. I now only use them in certain situations and seldom ever on my homestead farm. They are better reserved for the seed farm where it is drier and hotter. 
5- macnut harvest debris (husks and shells) make a good mulch for me, but alas they are costly. So I don't use it much. 
6- shredded green waste from the county. I'd use truckloads of this stuff if I had easy, cheap access to it. At one time I did. But not anymore, sigh. 

Mike had two more questions..... How often do I need to reapply mulch? What do I do with the surface mulch when I need to dig or till the soil? Um. How about if I answer those on another post. Otherwise I'd be writing a book here.    :)

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