Commrcal vs Org fertilizers for compost
Hey guys this is interesting. I gotten different feed backs on using fertilizers on composting leaves and grass clippings piles to quicken up the composting. The feed back that I have gotten is that commercial fertilizers interfere with the microbes that break down things in compost.
O.K. The most limiting factor usually in composting is the availability of nitrogen. (well I guess it depends on what you are composting…if it’s green grass clippings, nitrogen may not be such a limiting factor vs say fallen leaves or wood shavings) Either way can someone give me a study that shows that fertilizer interferes with microbes? I’ve learned that organic nitrogen is simply something not in its mineral form. For things to be taken up by a plant they need to be in mineral form. The bad rap on commercial fertilizer is that it is water dissolvable so it can easily be leached while organic nitrogen, things that are still bound in leaves, grass clippings, or manure are not mobile. They must break down into the mineral form to be dissolvable in water and then cause a threat. So things like manures etc are greener b/c they take a while to break down, so they act like slow release fertilizers.
So, I’m trying to figure out how commercial fertilizer interferes with microbes. Maybe the interference comes in b/c the microbes feed off of organic stuff that is full of nitrogen and perhaps they don’t take up nitrogen in its mineral form. Is that why commercial fertilizer is not good to use in compost? I’m just putting out what’s out there. I just need more information. Thanks!
~Davis
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(post #11148, reply #1 of 7)
That's a really good question. I had wondered about that and as a chemist I could kinda see the problem but I'd never taken the time to research it. Here's a link.
http://www.ecochem.com/t_faq9.html
It doesn't go back to the basic research but it looks like a pretty good answer.
BJ
(post #11148, reply #2 of 7)
That's been the conventional wisdom for a very long time, but when I went to search for a reference, I was disturbed that most of the sources were from organic sites. They're almost always slanted against chemicals and don't usually cite peer reviewed, published studies. I knew I had read many, many years ago about using synthetic fert (ammonium nitrate) in compost, so I tried a different search. It wasn't much better, but I found the site below about using it instead of high nitrogen green materials. I still believe that the microbes are better off without the harsh ureic acid, but here's another method: http://pubs.ext.vt.edu/426/426-703/426-703.html
Jeana
Never try to baptize a cat.
Edited 11/12/2009 12:55 am by Jeana
(post #11148, reply #3 of 7)
Commercial "fertilizers" are usually single shot doses of various kinds of mined materials, like lime, or sulfur, etc. suggested to increase the fertility of your soil. Because they are specific, they are not "all around."
I don't use anything but my garden clippings and manures and leaves if I can find some. I live up in a fir forest area and have some local grasses also. My compost seems pretty good.
Many commercial products are mined from large deposits of specific types, like coal, sulfur, etc.which are left over in huge deposits after flooding, with the lighter elements appearing at the surface, and heavier deposits, like coal, at deeper levels.
A compost heap with a mix of all the kinds of local weeds, grasses, wood, egg shells, leaves, grass clippings etc. you can come up with have many of these elements in the plants you put in your compost heap, on a small scale.
Your own compost is the best way to include the vital soil elements which your own garden and yard contains and should thrive on.
New Mexico home organic gardener
Adopt the pace of nature; her secret is patience. Emerson
Edited 11/12/2009 5:21 pm by Astrid
(post #11148, reply #4 of 7)
Most all synthetic fertilizers are acicdic in nature and that could cause problems with the bacteria that are supposed to digest your compost materials. Unless you add some really high Carbon material, such as sawdust, to your compost you probably do not need that much more Nitrogen in the mix. Grass clippings have a C:N ratio of about 16:1, tree leaves can range from 40 to 80:1, and most all of the garden or kitchen waste will also be fairly close to that optimal 30:1 CLN ratio.
All the plant nutrients you can add to your soil need to be converted into something the plants can use by something and that something is the soil bacteria, the Soil Food Web. Since synthetic fertilizers can create an environment in the soil that is not very nice to live in, why use them?
The sign of a good gardener is brown knees, not a green thumb.
Let's look at this issue by (post #11148, reply #5 of 7)
Let's look at this issue by nutrient.
Nitrogen whatever the source (commercial or organic0 must be in the form of NH3+ or NO3- to be taken up by plants or microbes. That means that all the organic compounds must be broken down to be useable. Mineral N is allready in a useable form. Problems with mineral forms relate to excess application; not the form. On the other hand mineral forms of N are pure(except for steel mill buy-product ammonium sulfate).
Phosphate sources must be broken down into H2PO4-, HPO4-- or PO4--- ions to be used by plants. These are the forms already present in mineral fertilizer while organic sources be they plant or animal, such as bone meal, must be decomposed to these ions to be used. Again the sutibility is one of rate of release and acidification of the soil as the ion is taken up by the plant leaving behind an acid condition in the soil. In the case of phosphate materials the more concentrated (higher the analysis) the less the chance for undesireable elements to be included in the product.
Potassium(Potash) is available in several mineral forms Potassium Chloride(KCl), Potassium Sulphate(K2SO4), Sul-Po-Mag(a combination of potassium and magnesium sulphate) Potassium Nitrate(KNO3). Only the manufactured Potassium Nitrate is chemically pure. The mureate(potassium chloride) when dissolved in the soil solution, and the K- is taken up by the plant, leaves behind an exsess of chloride ion which will leach from the soil, but are not particularly benificial in the soil.
In short mineral fertilizers are not harmeful to plants and provide the same ions for plant uptake as organic sources. It is the timeliness of the release that needs to be controled.
These same criteria apply to helping microbes breakdown compost.
The problem is not with the (post #11148, reply #6 of 7)
The problem is not with the potassium, nitrogen, and phosphorus in the commercial fertilizer, it's the salt that is also present. Just as fresh water fish cannot survive in salt water, microbes that break down compost will not do well if too much salt is present in the organic material they are trying to break down. Salt can be used as a mild disinfectant just because it does kill bacteria. Of course, all water in nature contains trace amounts of some salt (except perhaps for rain and snow as it's falling), so it's all a matter of the salt concentration and the salt tolerance of a particular strain of bacteria.
As I said some commercial (post #11148, reply #7 of 7)
As I said some commercial potassium products have high chlorine content; but even that is completly soluable and mobile in the soil and under normal rainfall will be leached from the root zone. Potassium and ammonium nutrients may be formed with sulfates which are also soluable under normal conditions and are normally present in the soils and supply the needed nutrient sulfur.
If you really want an material free from non nutrient ions you can use: ammonium nitrate, potassium nitrate and/or ammonium phosphate made from 100% pure industrial chemicals. None of these leave residual salts.
Further as said before, excess salts in soil or compost in this case are from excess application in relation to plant useage and rainfall.