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experiences with adding chop and drop mulch in arid conditions?  RSS feed

 
shauna carr
Posts: 84
Location: Sonoran Desert, USA
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I'm wondering about everyone's experiences with mulch, like chop and drop mulch, in arid conditions. Does it desiccate too quickly to be as useful? Does it seem to help the soil? Does it actually add nutrients back into the soil or do you do better with planting leguminous plants and trees, or using bioaccumulators, instead?

I'd been wondering about this and happened to come cross this abstract that made me wonder even more.
http://onlinelibrary.wiley.com/doi/10.1002/ldr.2250/abstract

"This work studies the influence of two mulching treatments on soil properties and the field performance of afforested holm-oak seedlings (Quercus ilex L. subsp. ballota (Desf.) Samp.) nine years after outplanting. Mulching treatments composed of stones, forest debris, and an untreated control were randomly applied to 180 seedlings ... in SE Spain. Survival, growth measured by means of leaf area, and nutrient concentrations in leaves and soil were measured. Both mulches provided higher survival and greater leaf-area growth than the control, but did not differ in leaf-nutrient concentration. Most of the analysed soil variables were not affected by the mulching treatments at the end of the study period, and, therefore, the soil properties changes by mulching might be slower than expected under semi-arid conditions. Copyright © 2013 John Wiley & Sons, Ltd." [emphasis mine]

 
Bryan Jasons
Posts: 62
Location: Maine
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I don't know anything about desert mulching, but you mentioned legumes... If you wanted to try an experiment, then growing Moth bean as an annual ground cover might be interesting. Since it's a living ground cover it won't desiccate quickly like mulch would :

http://www.bountifulgardens.org/Moth-Bean-Mat-Bean-Mother-Bean/productinfo/VBE-2370/

http://en.wikipedia.org/wiki/Vigna_aconitifolia
 
Jennifer Wadsworth
Posts: 2679
Location: Phoenix, AZ (9b)
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I think chop and drop type mulching is much slower to decay in arid climates - you need water to decay. Chopping things up as finely as possible will help. As will planting in or around infiltration basins (concentrating water runoff for decay to happen). I've gardened in tropical, cold humid and arid climates. In tropical gardens, things break down rapidly all the time as there is both heat and water. In cold climates, stuff breaks down pretty quickly throughout the year but the thaws and warming of spring really do break down a lot of matter. In the desert, things desiccate.

What I usually do if I lay down carbon rich mulch is water the soil down a day or so before application. Then I add some finished compost or a little manure or whatever else I may have on hand that might have microbes in it like compost tea. Then I soak the carbon material in water before applying to the damp soil. I realize this seems water intensive (sometimes I'll water with kitchen sink water or laundry water if it is within easy walking distance) but I only do this one time. This jumpstarts the interaction between the soil and the carbon mulch (hyphae net) and stops the carbon material from having an initial wicking effect on the soil. I try to layer on mulch as thick as 8" if possible. I also lay any irrigation lines between the soil and the mulch.

I have a friend a block away. She got a large amount of woodchips that she moved to her backyard with a wheelbarrow and just dumped out in piles. She never raked them out or anything. Google earth pics of her property show all the little mounds! Now, 4 years later, about 2/3 of the chips are gone and the ground underneath has about an inch of rich looking soil. This area never got any additional water either. Soil building by mulching is much slower going than in other places, but definitely worth it. A stat out of the NRCS said something to the effect: "for every 1% increase in soil organic matter you increase the water holding capacity by 5,000 on 1 hectare" (this is from memory from one of their emails.
 
Jennifer Wadsworth
Posts: 2679
Location: Phoenix, AZ (9b)
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@Bryan - thanks for the Moth Bean info!

Also, tepary beans are native to this neck of the woods. I've also had a lot of success growing black-eyed peas in the summer (go to a natural foods store that sells bulk beans, grains, etc and buy black-eyed peas). Limas do ok in summer and will make vines about 5-8 ft tall so they can be used for shading.
 
shauna carr
Posts: 84
Location: Sonoran Desert, USA
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Thanks! I had not even thought of a wicking effect, but that makes total sense. I haven't tried limas out here - tepary beans have done all right, but they've been kind of scraggly. I'm trying to figure out what they need that they weren't getting from me.

Chopping things up sounds like a good solution to the slower breakdown - I had a bizarre success with helping things breakdown once by accident, and now I do it on purpose.
I have a big glass jar with a cover (not completely sealed so gas could escape, but heavy enough to rest on top and keep moisture in) that I keep veggie scraps for composting in. Once, I put it outside for the purpose of putting in the garden compost later, and then left on vacation, forgetting about it, and came back a month later to a jar of sludge, basically. This has become what I do now for 2-4 weeks to my jars of composting stuff, before i put them in the ground, and it's really sped up the break down from what was happening in the ground.

Bryan - the moth bean sounds interesting! I think it might be a bit TOO vigorous for what I would like to do in most areas - I'm trying to keep a lot of the native plants, if I can. I am not zoned for most animals, and the ones I am zoned for, I'm allergic to! >_< So attracting a lot of local critters has become part of my sustainability plan - they add a lot of my manure to my yard for me and keep the pests off my garden. But I have a few plots the moth bean might be really suited for. Thanks!
 
Alder Burns
pollinator
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Location: northern California
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The longer I live in comparatively dry California (contrasted to GA and MI, where I used to live and garden) the less and less enamored I am of mulch as the solution to every problem in the garden. It's becoming more and more of a habitat for earwigs, pillbugs, and slugs. If I bury drip irrigation hoses in it, rodents are much more likely to chew holes in them than if I have them on the surface of bare soil. I've been trying to subdue bermuda grass with cardboard sheetmulch, and have one area two years in and it's still popping up here and there. No way can I plant through this until it's gone completely or it will come up through the gaps I make for the plants and then I have a huge mess. Better to leave it unmulched and I can keep the bermuda subdued with a hoe once a week or so.....
I've read that ducks are the real solution to the ground bug situation, and their bills might do fine through a fluffy mulch, minus the paper and cardboard. They're in my one to two year plan.
I think part of the problem is the ecosystem is naturally somewhat depauperate compared to the rainier East, and when I stimulate plant growth by means of irrigation, and mulch, then the first thing to proliferate are pest insects (and plant diseases, too, surprisingly). There aren't naturally enough predators and parasites in the system to keep them subdued, yet; as I suspect there were elsewhere.....
 
Nolan Robert
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Do you think adding mulch or sheet mulching could capture water when it rains?

When it rains on my property, the soil is sandy, and the water just runs right off.

I'm thinking that if I sheet mulch and do mini keyline rip in between the sheet mulchings, It should soak in water as opposed to the water running off.

If this works, than I think it could be useful to have mulch in arid or semi-arid areas, even if it doesn't have a nutrient value.
 
Tami Clark
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I too live in arid California, Northern California to be exact. I have had the same problems with Bermuda and sheet mulching. I have found the best way is to leave the bermuda bare, and dig it out. After about a year, and working on it every other month or so, I have been able to get rid of it in my garden areas. It does take diligence tho.

I have also had a slug and snail problem with the sheet mulch and straw, but have found the water savings and the weed control more than worth the effort. If you mulch with rice straw, which is much finer than regular straw, you can easily pick the snails and slugs out on early morning wanderings - they really stand out. Hand picking seems the way to go.

Just a few thoughts
 
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