Comparing Mulched Soil to Bare Soil

[Durgan]

http://www.durgan.org/URL/?OAZIE 21 June 2012 Comparing Mulched Soil to Bare Soil.
The difference between mulched soil and bare soil can be astonishing.This is an example, not anywhere near the extreme. I have seen bare soil as hard packed as cement. Bare soil is not beneficial to the plants. Obviously I am a great advocate of mulching. I have seen no downside to mulching.

[dustydave]

For bacteria to break down the mulch they require available nitrogen and carbon, they cannot get these from the mulch (until they have been broken down) so they take them from the only availabe source - the soil. So adding mulch actually reduces the nitrogen content of your soil. Much better to put it on the compost heap, let the bacteria do its thing there, then add it to the soil.

[gregorach]

Mulching certainly can be extremely beneficial in some conditions, but not all... It depends very much on the soil and the climate. We don't usually have to worry too much about water retention around here... Quite the contrary, in fact.

[Durgan]

For bacteria to break down the mulch they require available nitrogen and carbon, they cannot get these from the mulch (until they have been broken down) so they take them from the only availabe source - the soil. So adding mulch actually reduces the nitrogen content of your soil. Much better to put it on the compost heap, let the bacteria do its thing there, then add it to the soil.

Agree with what happening in the laboratory, but this minor nitrogen depletion, I don't know about the carbon, can be overcome by adding by adding a bit of Urea if necessary. I rototill these chips into the garden in the Fall in some cases sprinkle Urea as a precaution and have never seen a deficiency of nitrogen in my plants. In practice the process may be more hypothetical than real. The moisture saving advantages far outweigh any possible loss of nitrogen (easily replaced). Carbon first I heard of it being mentioned. Also if just used as mulch and not worked into the soil nothing happens of significience. In nature the forest is covered with mulch, which is basically wood. How does the theoretical propagator of nitrogen deficiency explain this with regards to the magnificent growth in these areas? Maybe it is much ballyho about nothing.
http://vimeo.com/28055108 Watch this tedious video. It takes effort.
There is too much evidence that mulch is beneficial to ignore its use.

[Odsox]

I agree with Dunc that you can't make such generalised statements.
I do agree that mulching is probably beneficial in your situation Durgan with your soil and climate, but in other situations it is possibly detrimental. Climates with regular rainfall like mine, a thick covering of coarse wood chips on my garden would be a haven for slugs and woodlice which would make it all but impossible to grow any vegetables, especially salads, without resorting to slug pellets etc.
Also wood chip mulch in a high rainfall area would make for very acid soil which could lead to very disappointing results trying to grow any brassicas without considerable liming.
You have to remember that there are inexperienced gardeners in many different micro-climates who look to this forum for guidance.

[boboff]

I like mulch it is so much easier to handle as it reduces weeding.

But.

1. Why can't the Nitgogen come from the air?
2. You don't get a composting "heat" from a mulch, so surely any reaction is very slow.
3. Not only climate but also what plants you are growing will have an impact, the dry soil od Durgans looks good for Rosemarry & Lavender to me, Mulched "Forest" soil is going to be loved by plants like Raspberries and Jacobs ladder?
4. Adding wood chippings will acidify your soil, given most plants prefer a slightly acidic soil, I can't see this as an issue, plus it depends on what you start with.
5. I think even the most inexperienced gardener should know better that to take just one persons view, as advice and action and experience combine don't we all make up our own minds? My Gran tuts at me for using wood chip Mulch, same complaints as Dusty Dave, in my experience however I get less weeds, less slugs, and better plants using a mulch than not, BUT I know the reason for this is without out I don't weed enough, so the "robbing" of nitrogen which is a fact I am sure, is outwayed by the fact the plant gets more sun, and less competiton?

[Odsox]

1. Why can't the Nitgogen come from the air?

This reinforces my point Bobof, nitrates and nitrites in rain needs thunderstorm activity and in the 18 years that I've been at this location we have only had just the one thunderstorm, so very location specific.

4. Adding wood chippings will acidify your soil, given most plants prefer a slightly acidic soil, I can't see this as an issue, plus it depends on what you start with.

Again this is totally depends on your location, my soil is peat based and gets on average about 80" of acidic rain every year. Try growing cabbages in that with wood chip mulch as well.
My point is that you can't make generalised statements when everyone has their own unique set of circumstances.

[boboff]

Absolutely, I do agree with you about the set of circumstances, 100% but that should never preclude a poster on a forum posting generalised statements based on their unique set of cicumstances? should it?

No it shouldn't, it's up to the reader to take any pertinent information and use it or not, Mulch and Wee Mulch and wee, although I have had two indecent exposure prosecutions in the last 6 weeks!

I don't think anyone would seriously consider juicing lettuce, so why would we all become 100% Mulch converts because Durgan Says?

No I don't even know what I am saying anymore, forgive me. It's time to get a life.

[gregorach]

Absolutely, I do agree with you about the set of circumstances, 100% but that should never preclude a poster on a forum posting generalised statements based on their unique set of cicumstances? should it?

Obviously not, and I don't think anybody is suggesting that it should. We're just adding more information for people to consider.

[boboff]

I agree with Dunc that you can't make such generalised statements.

[gregorach]

Well, that's not how I interpreted that particular statement, but I'll let Tony explain his intent himself.

[boboff]

Obviously not, and I don't think anybody is suggesting that it should.

[gregorach]

What are you trying to say?

[The Riff-Raff Element]

1. Why can't the Nitgogen come from the air?

Nitrogen as it is in the atmosphere cannot directly be utilised by plants. To become so it needs to be converted either to an oxide of nitrogen or to ammonia. There are three routes:

- Via lightening strikes where the air get hot enough for oxygen & nitrogen to combine directly (tiny amounts);
- Fixing by bacteria associated with the roots of some plants - peas, beans, clover, vetches, alfalfa, etc. This used to account for almost 100% of the nitrogen fixed, but now it's more like 60%, because:
- Chemical fixing of nitrogen via the Haber process which uses vast volumes of hydrocarbon.

I worry about mulches pulling nitrogen from the soil as they decompose, but I'm probably over reacting because I use planty of manure, make compost and plant nitrogen fixing green manures. Around permanant fixtures like friut bushes they make my life a lot easier, but where I'm turning the soil over I avoid them. But I don't have to worry to much about drought. I might think different if I did.

[grahamhobbs]

Woodchip is not the only mulch you can use, you can mulch with compost, rotted manure or grass clippings, which avoid the possibility of robbing the soil of nitrogen, acidifying the soil or of encouraging slugs.

Mulching is much better than bare soil, so long as you use the appropriate mulch for a particular situation. For me mulching with woodchip is fine around most soft fruit but not many other places.