Organic mulch for raised bed

Question

I have 3 raised beds in my backyard where I am growing vegetables (tomatoes, bell peppers, etc). Right now, I don't have any mulch covering the soil but am thinking that would be a good thing to do to preserve moisture in the soil particularly as summer is upon us. I am only using organic materials in the vegetable garden (no pesticides, organic fertilizer only) so wanted to know what organic mulch are people using?

Answer 1

I quite happily steal from the lawn (and neglected hayfield, if you have access to one) to feed the garden - fresh grass clippings make a great mulch IF you don't get them more than 2-3" deep in any one application - they mat well, but that's thin enough that they don't turn into hot slime as they will if piled 6" or more deep. If you can source newsprint to go under it, so much the better; that's not quite as widespread a resource as it used to be.

You can even get more creative and plant a part of the lawn to alfalfa, vetch, clover or other things that you then cut specifically to make mulch from. Kinda depends how much you have the "lawn" disease .vs. how much you are willing to suborn that to garden purposes.

I enjoyed the smell of cocoa-husk mulch, but was not over-fond of the price, nor the tendency to mold. May also be a hazard to dogs (not a problem for my garden.) "Mulch hay", if you are near enough to agriculture to get it easily is hay that got rained on too much to be good animal feed, and cheap. Hay or Alfalfa that are good enough for animal feed are also good mulch, but more expensive. Cubed alfalfa is widely distributed, even in not-so-rural areas. Pine bark and cedar are essentially useless, and also the most common bagged mulches for sale. Straw is nice, but in my area costs more than feed quality hay.

Shredded leaves/leaf mold are good, (though leaf mold is pretty much right up there with "mulch with compost" - nice if you have too much of it, but that's a problem it's not common to have, in practice. And you may not HAVE a large quantity of last fall's leaves handy NOW.

Wood chips are OK when you have a semi-permanent path layout, for paths - not so good as mulch on beds.

Answer 2

The French biointensive method doesn't use mulch but closely grown plants. The leaves overlap and create a microclimate which didn't need mulching to trap moisture.

But since it's too late now, I'd just use tree mulch which is usually pretty cheap, if not free. As long as you don't mix it in the soil, it ain't going to steal much nitrogen.

Answer 3

For raised beds, I recommend mulching between rows with browns (shredded leaves) and near plants (where you hoe) use compost.

Then, at the end of the season, you have browns already in your garden, and can till in green compost (or a good nitrogen composted manure, which is cheap) and boom - soil rejuvenation is taken care of.

If you lack a supply of shredded leaves, (actually, anything I write here is just a variation of "get a garbage bag and go get some).

If you find the soil too settled next spring, I find diatomaceous earth to be an amazing amendment for drainage and aeration. (Napa Auto Parts, Oil Absorber #8822). You can also mix 50/50 with Bentonite, which is a more expensive name for Arcillite, which is a fancy way of saying Calcined Montmorillonite Clay, which you can find for $8 a bag at Auto Zone, also as an oil absorber (made by the same company as the 8822, EP Minerals).

Remember a little goes a long way with drainage amendments, and adding more is easy while removing pebbles and sand is a pain.

Back to the mulching - make it work for you instead of turning its removal into another end-of-season chore. Using browns for between rows is a time-tested method, and it's especially good in raised/isolated beds where nutrients are removed by plants. (Also, don't forget the lime every couple of years - use lawn lime, it's a little less concentrated than Garden Lime, but it's the same minerals and 1/5 the cost).

Answer 4

For the vegetable garden I like using black plastic mulch. 3 mil or thicker black poly sheeting is readily available at hardware stores and is inexpensive. It is not an organic substance but it is allowed under the National Organic Program provided it is removed at the end of the season and it's not PVC. See Allowed Mulches on Organic Farms.

Other than plastic mulch I like items that decompose quickly so they're virtually gone by the next spring. Grass clippings are great provided you care for your lawn organically or don't use herbicides. They have a lot of benefits but I don't like robbing my lawn of those benefits any more. You can collect and save fall leaves and use them as is or make leaf mold over the winter. Straw is a popular choice. There are less weed seeds than hay. Paper, newspaper and cardboard that are not glossy and don't have glossy inks can be used as a base and then something more attractive on top like grass clippings, leaves or straw. A thick 3" layer of compost is also used for mulch which seems counter-intuitive since things grow well in compost but if it's thick enough it will suppress weeds. If you see a weed popping up in it it's usually easy to pull it out if you catch it young. It's also great for your soil.

I know there are other no-till options but I till my vegetable garden beds in early spring to clear out old roots and incorporate fertilizers. For that reason I don't like long lasting mulches like wood chips. I did try some of those compressed coir mulch blocks last year. It worked well, looked nice and was easy to use but not enough of it broke down the next year. Looks like maybe 2-3 years to break down but it can be tilled into the soil.

Still, black plastic poly sheeting is cheap and easy, has many known benefits and is NOP approved. I like it because it helps warm the soil and I can plant earlier, suppresses weeds, retains moisture and has been shown in university studies to increase yields. Red plastic mulch has been shown to increase yields even more but the black plastic is easier to find locally and cheaper.