Discussions on Compost vs Mulch
(7/7/03 - 7/16/03)

______________________________________________________________ postings: 8
countries: France, Germany, Honduras, Nicaragua, USA (Hawaii)
organizations/institutions/companies: Association Las Encantadas, CATIE-MIP, COSECHA, GTZ

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Date: Mon, 7 Jul 2003
Subject: "Efficiency" of compost vs mulch
From: Stephan Reeve
To: MULCH-L@cornell.edu

Aloha,

Does anyone have any data comparing the efficiency of the transfer of organic matter to the soil through composting vs mulching?
There must be some loss of nutrients and "energy" in the breakdown of mulch as well but I imagine it's not as high as 50%. I almost always recommend mulching over composting for the bulk of inputs but I'd like to have a better idea of the dynamics of the mulch materials.

Steph
Hana Maui, Hawaii, Pacific Ocean

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From: Rolando Bunch
To: Stephan Reeve
Date: Tue, 8 Jul 2003
Subject: Re: "Efficiency" of compost vs mulch
Organization: COSECHA, Valle de Angeles, Honduras

Dear Stephan,

We do have some data on N losses of mucuna mulches here in Honduras, and they do go over 50% of N if a) the mucuna is mulched all alone (ie not together with maize stalks, for instance), b) the field is below about 500 mt in elevation, and c) several months pass before another crop is planted. Nevertheless, even so, the total amount of N fixed and maintained (and therefore ADDED to the system) is still substantial, whereas a compost heap never adds to the system, unless materials are brought from outside the system (which usually means additional costs above and geyond the labor costs). After all, mucuna, for instance, fixes about, say, 100 kg/ha/year to a field. Even losing 50% of that, there is a net gain of 50 kg/ha.

And the total cost of that N (taking for example the North Coast System) is negative, because the management of the mucuna has, in fact, cost a good deal less than the labor saved the farmer in weeding work, or in the cost of herbicides and their application.

Thus, even if we lose half the nitrogen from the mucuna, what was lost (as well as what was left) was free. Not a big deal. Furthermore, that loss of N is probably responsible for the fact, also shown scientifically, that the mucuna mulch was not causing acidification of the upper layers of the soil, as we previously feared might be the case with so much N being added to the soil.

Sincerely,
Roland Bunch
COSECHA
Tegucigalpa, Honduras

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Date: Wed, 9 Jul 2003
From: "Steiner Kurt 1030"
To: <MULCH-L@cornell.edu>
Subject: "Efficiency" of compost vs mulch

Dear Rolando,

Thanks for the info sent to Stephan, which is also of interest for me. From all my research and development work in Africa, I do no longer believe that compost is a feasible practice for farmers, except for small home gardens. Due to lack of transport facilities and thus high cost of transport, organic matter has to be produced in-situ. Where we can protect it from cattle and fire, we have excellent results with Mucuna and Dolichos mulches (planted as relay crops under maize). Added to the fixed nitrogen is a higher P-status, an increase of rainwater productivity (about three times, which means increased food security) and then of course the weed control. Labour saving for weed control is the main incentive for farmers to go for direct planting. Especially in Africa, where labour is becoming extremely short due to outmigration and HIV/AIDS, new farming practice must be labour saving. Compost and compost teas may have their benefits but are not economically feasable (except! perhaps in peri-urban and urban horticulture).

Best regards,

Dr. Kurt G. Steiner
Senior Technical Advisor - Sustainable Land Management
GTZ Dpt. 103/45
P.O.Box 5180, 65726 Eschborn/Germany
web: www.gtz.de/conservation-tillage

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From: "jamie" <jamie@tiscali.fr>
To: <MULCH-L@cornell.edu>
Subject: RE: "Efficiency" of compost vs mulch
Date: Tue, 8 Jul 2003

Hello Stephan, in another post I tried to express soil as being a live entity, the fact that a handful of healthy soil contains more creatures (of many different sorts) than there are people on the earth, expresses something of the vital nature of this life.

Mulches, of whatever nature, will be broken down by the microorganisms (MO) whose role it is to break down the surface litter layer, transforming it through excretion, predation and death into other forms that are used by other MOs or plants.

Mulches therefore do not lose nutrients (at all) or energy (except to maintain the MO) as do composts. By using the ubiquitous natural process of the breakdown of surface organic material, mulches are the most effeicient way of getting nutrients into the soil in a plant available form.

Although composted material will give to the soil a quick boost, as the nutrients are already available for the plants, this 'speed' hides the time it took to produce the compost (and the energy lost in its production) and the fact that such a sudden boost will destabilise the balance of the soil organisms. Therefore, unlike Roland, I would suggest a plentiful supply of mulch, living and organic, rather than compost for even the most intensive cultivation - because, ultimately, soil will only produce what it can produce without some decline in fertility. Or, to put it another way, there is a limit to the yield of any given land if we wish to be sustainable.

Jamie Nicol
Association Las Encantadas
France

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From: "jamie" <jamie@tiscali.fr>
To: <MULCH-L@cornell.edu>
Subject: nutrient losses in mulch
Date: July 11, 2003

Hello Roland, thanks for the mucuna information, it certainly highlights the generalising inadequacy of my 'no nutrient losses'. Do you have any idea of the mechanism of this loss and how the incorporation of other mulch material and altitude affects it?

Working in a temperate climate I've not been aware of any appreciable nitrogen loss: the breakdown of Medicago lupulina (black medic - drought tolerant, mediterranean France, nitrogen fixer) seems stable. Perhaps tropical rain and/or heat facilitates the N loss through leaching or off-gassing (as N2, NO or NO2)? I know that temperate climates retain and cycle about 95% of nutrients in the soil, whereas perhaps only 75% of nutrients can be found in tropical soils - the difference being locked up in the vegetation itself. Perhaps this accounts for our differing experiences. It also indicates the relative importance of maintaining live mulches on tropical soils (as I know you do) to temperate soils and why so many of the techniques exported from temperate countries have been so disastrous for tropical agriculture.

If you know of an internet source that describes the physical or chemical pathways of N losses I'd very much appreciate it.

Jamie Nicol
Association Las Encantadas
France

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From: Charles Staver
To: <MULCH-L@cornell.edu>
Subject: breakdown in situ vs compost

I am intrigued by the comments that the energy lost in compost production would have a positive effect if the same material were used as a mulch and the breakdown would occur in the soil. What is the effect of the breakdown process of organic material other than the addition of nutrients and the final humic components. The biological activity itself has a positive value?

Charles Staver
CATIE-MIP
Nicaragua

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From: "jamie" <jamie@tiscali.fr>
To: <MULCH-L@cornell.edu>
Subject: RE: breakdown in situ vs compost

Hello Charles, I'm using the ideas expressed by Gilles Lemieux (http://www.sbf.ulaval.ca/brf/) to make my comparison between mulch and compost: this is what Lemieux actually says:

"... la fermentation thermophile, principalement à base de bactéries et d'actinomycètes, provoque une perte d'énergie importante par la dégradation des sucres, polysaccharides de toutes sortes et plus encore des nombreuses protéines et acides aminés présents dans la partie des arbres et arbustes où se fait la photosynthèse et où s'élaborent les produits les plus complexes du métabolisme. Il faut ici reconnaître des pertes de l'ordre de 50% et plus lors de la fermentation."

...roughly translated...

"...the heat generating fermentation is based mainly on bacterial and actinomycetic activity, which creates an important energy loss through the degradation of the sugars, polysaccharides of all kinds and more still of the many proteins and amino acids present in the branches of trees and brush where the most complex products of a plants metabolism are created through photosynthesis. It is necessary to recognise losses of 50% or more during this fermentation."

He is specifically addressing the type of compost elaborated by Jean Pain in 'Un Autre Jardin' or 'Another Kind of Garden' as the book is known in English. Pain cut the brush beneath the oak forests of Provence, France and then composted the leaves and branches to get a compost he then used to mulch (surface layer and not dig into the soil) his vegetables that enabled him to go through the dry summer without watering.

I think it should be noted that Lemieux is talking specifically about lignin based composts/mulches (ie wood) and that his preferred technique is to use the chipped wood of branches of 7cm or less; although I don't think the general point of losses during the heat of the composting process will change radically with varying organic matter.

At the expense of belabouring the point, although with the intention of drawing the point back to the necessity of an active and diverse MO soil population for the proper functioning of the nutrient cycle, I'd also like to mention that Lemieux has developed a hypothesis that twigs not only provide the soil with nutrients but also act as a support for a great number of biological processes that regulate the sysnthesis and release of nutrient, minerals and biochemicals. It seems that the nature of lignin and the position of methoxyl groups in the wood could play an important role in the retention and availability of water in the soil. The chipped wood provides the soil microbial activities, says Lemieux 'espicially through the activity of Basidiomycetes because we consider the young lignin to be the main stable factor using those oligomers to be depolymerized. From this depolymerizing process, monomers are then used to build up humic and fulvic acids the basis of pedogenetic process through complex enzymatic activities from which there is further transformation'."

I interpret this to mean that only at normal temperatures (not the high temperatures found in compost piles) will organic matter be broken down into those stable factors that are not only beneficial to the soil but are the basis of the soil forming process. It is quite a claim by Lemieux but one that he has replicated not only in his native Canada but elsewhere in very different climates such as Senegal.

Hope this helps,

Jamie Nicol
Association Las Encantadas
France

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From: rolando
To: "jamie" <jamie@tiscali.fr>, MULCH-L@cornell.edu
Subject: Re: nutrient losses in mulch

Dear Jamie,

Yes, I believe that the ambient temperature has a lot to do with how much N is volatilized. What the specific mechanisms of this volitilization are, I am afraid I have very little idea.

Sincerely,
Roland Bunch
COSECHA
Tegucigalpa, Honduras