I have a chemical reasoning, I can't reason without the chemistry, I search a chemical explication in every thing. First of all, the process involving the substrate's aging must understood because the big problem is found exactly there and we had the preoccupation to do a work about this.
You cultivate the plant in substrate no matter which, if it is a orchid in tree fern fiber, sphagnum moss, piassaba, wood log or in any kind of substance and as a result of the passing time, you notice that it is growing older.
The big question is, what is the aging of the substrate?
We concluded that the substrate is being attacked for fungi, bacteria, or to put in another way, there is a very intense microbial flora which has an important place, indispensable to life in earth. This microbial flora decomposes the organic material, changing it into humus creating a series of substances which are important to the plants. This was our way, our work has been based on it.
Of course, plants can't eat a piece so nutrients must be soluble in order to be absorbed by them.
How can the plants get it, how is this process?
Precisely by the action of the bacteria which attack the organic residues provoking the slow decay until reach mineral kingdom under the form of simple mineral, nitrogen, hydrogen,, etc... So, if the substrate doesn't decompose, you can notice, at first sight, that is a bad substrate because it doesn't provide the elements the plant needs.
Why is the tree fern, without favor, the universal substrate?
Because it has an enormous amount of cellulose which is gradually decomposed, not too fast, it has a control on the decomposition and going on generating humus during a highly complex process. First, the group of germs comes in, all aerobes, then other groups, bacteria, fungi and so on. It gets a point where we will have the humus which is formed essentially by the decay of vegetal matter. That is something we can see every day. We assemble an amount of leaves, vegetal detritus, keep it humid, this material starts decomposing and, gradually, it takes an appearance of earth, dark, integrally returning to mineral kingdom. If the anaerobes bacteria get in, if the material is closed interdicting the aeration, it can generate compounds absolutely undesirable, anaerobes conditions which are not the ideal to produce de humus, creating a decayed, alkaline compost which can provokes serious problems .
When you pour too much water in the substrate, you provide an anaerobes medium, that is, the oxygen held within the water is wasted away because some reducing substances are generated inside the substrate, to put in other way, they are arid of oxygen and take it from the water, creating anaerobes conditions. Water in excess, among other things, is harmful because of this.
When you compact too much the substrate, you have the same problem. I am not well inclined to organic fertilizer although I am not completely against but it should be used very careful and with orientation because it forms a layer, a covering which closes the substrate also generating those anaerobes conditions.
There is a classical experience, take two plants with new roots, still green at the tip, put one into a glass and cover it with substrate very well pressed. Put the other one also into a glass but the substrate layer should be thinner, free. After some days, take them off, the first one, with a compact substrate, is dead and the other one, will be alive.
The nature gives us an important lesson about it. How do we find the plants' roots? Hanging, free, in the surface of the trees, of the stones or in earth extremely soft. A robust, well-fed, wonderful plant, in a very good cultural conditions, is, in general, found in ground where there are those leaves fallen down.
So, we know that a substrate which becomes anaerobes, without ventilation, is a harmful substrate. If it allows the aeration, gets decomposing, in a while, there will be the humus formation.
What is the humus?
They are chemical compounds, that is, fulvous acids, humus acid, humina which is a chemical substance not very well defined yet. In addition, it has a little of melanin, the same as we have in the skin, produced by the fungi, working, decomposing the vegetable matters. It is hard to say it is the most important but, at least, it is one of the most important components of the plants' life. It has a multiple action which allows and encourages the roots growth. It is also an stimulator, it encourages the absorption of many elements, nitrogen, potassium, as a matter of fact, it has a very important participation , indispensable to vegetal life. Finally, we can't conceive life without it.
There is a big, showy example and we saw it closely: The Amazon rivers. There are two groups, the white and the dark. Solimões is a white river and Negro is a dark one.
The fundamental difference is: The dark river lays down in rocky soil, where there is no clay and as the water is very transparent, we can see the profundity, we see dark because it has no color.
The other one runs through clayey soil, extracts a big amount of clay and has this turbid appearance. Who has been to Amazon, has already seen it, the meeting of the Solimões and Negro waters forming the Amazon river. One is dark, the other is turbid.
Those rivers overflow periodically, every year, inundating the parts of riverside lands, forming those big swamp lands over the woodlands full of dead leaves. It is known that the flora in dark rivers borders is very exuberant due to the high proportion of humus acid. The rivers extract it, carry and give it to the plants. As those overflows are really intense, some plants stay plunged and there is an enormous amount of humus acid.
Of course the other rivers do the same extraction however they have a high quantity of clay, that, combined to humus acid, finishes to hold, to sequester it. The clay is a holder substance as well as the humus acid is. There is a group of chemical substances which has the property of sequestrating. Certainly, when we talk about sequestration, we refer to metallic ions but the clay has an action very similar to them on the humus acid, the clay takes it away, out of circulation.
What does it mean? There is a big amount of metallic ions crossing over the water: sodium, potassium, iron, nitrogen and the sequestration is a chemical process, nearly to be physical, where the molecular body involves the metallic ion.
The perfect image is a capsule involving the ion. The plant has the capacity to assimilate this and ruptures the sequestration. In this process, the presence of humus acid is increasing every day, we water the plants, giving them a series of dissolved metallic ions, calcium, magnesium, potassium which are hold , absorbed by the plants. So the water of white rivers (Rio Solimões and some others) are poorer than the water of dark rivers and the flora is not so exuberant.
This is the basic evolution of the substrate: a decomposition until reaches the point to producer an amount of humus acid. The decay is getting increasing and reaches a good level where the supply is the ideal to the plant. Then the quantity of substances thrown into the substrate is so high that reaches an insupportable, an excessive limit and it becomes toxic.
The humus acid is an excellent stimulant (we can mention many other advantages) but it has two parallel problems, is a reducer and a sequestration agent. As a reducer, it takes away the oxygen doing a perfectly comprehensible curve: We have the substrate not yet decomposed, without humus acid, neutral to the plant, then, by the humidity action, propitious conditions are generated to the bacteria and they start to disintegrate and will form the humus, in the presence of humus acid.
The tree fern fiber with 6 months, a year of use, gets the ideal state where the acidity is not excessive. The pH level is good to the plant, giving the necessary substances. It has already disintegrated partially, internally decomposed, the bacteria have allowed the liberation of nitrates, potassium, nitrogen into their different forms - ammoniacal, nitric and so on. The assimilation is going on until to reach the level I've already told about and then becomes toxic for the plant.

When the level is reached?

It varies a lot because it depends on the humidity but the experience teaches us that a well worked substrate, not too much compressed, can last 4 years. Then, we can see clearly that the plants fall to suffer. However if the substrate has too much humidity, the decomposing is faster, if the temperature is high, it could be more intense.
To do an useful pH measurement, you shouldn't use fertilizers because they have, mainly the organic ones, a high pH level. For example, Chicken manure has pH 10 and the Ricinus communis' bran has also high pH. All those things modify the pH. The German growers have created the best way to water a plant, I've seen it in Swiss, they water more infrequently but when they do, they soak the plant to wash the substrate. It is a very smart thing because the substrate becomes saturated and the humus acid is soluble enough (not excessively). If the pH has not acidity, he is perfectly soluble. So, washing, the excess, mainly mineral salts, gets away and the substrate is recomposes. However we can not make the substrate new because we can not take away everything.
There is no endless substrate. Since the decay starts, it is hard to stop it. Even washed, the substrate remains full of bacteria. A cultivation medium was generated and the bacteria will work quicker than in a new substrate even after stopping the washing.
Basically, this is the substrate cycle.
We must reason, mainly, considering the tree fern fibers and then take the conclusion for the others.
Are pebbles a good substrate? No, they aren't. They have nothing to give to the plants. Everything the plants need, must be taken from the fertilizer.

In 1992, you have published an article in Orquidário about piassaba palm's fiber (Attalea funifera and Leopoldina piassaba) where it was considered as promising substrate. It seems that the presumed qualities weren't confirmed, can you explain why?

Exactly, promising. It has very goods characteristics, it is porous but it formed in big part by lignin that doesn't decompose.
I opened a pot where I used it 8 years ago and it still was in the same condition I put it. So this substrate can't be similar to tree fern fiber.
There is another point that we couldn't anticipate. It seems to me that the microbial flora search for a place to stay. It doesn't born anywhere, it won't grow in rocks and I think piassaba has something which rejects, decreases the quantity and the quality of microbial flora. If there is no decomposition, there is no feeding for plants. Since is the microbial flora that feeds the plant, when we put manure, we are concerning about feeding this flora. It does a more specific disintegration, better for the plant, gives many forms of nitrogen amonniacal, nitric, disintegrate phosphates under many forms. So the disintegration made by the microbial flora is, no doubt about, better than ours.
Day by day, you must reckon on those microorganisms to help to do the decomposition. Piassaba is a good support but it doesn't have nothing to give, it is a bad cellar.
More than this, it has a harmful fungus which provokes skin and eyes diseases. Something very harmful.
The first time, I went to buy it, I was informed about a serious problem with the employees but I didn't pay too much attention. I am very strong for this kind of things, I'm hard to be attacked but I had a serious problem. It was enough to open the container and had skin and eyes problems. Of course, you can cultivate under hydroponics culture but it is a hard work, something extremely complicated, you have to deal with a lot of things, with deep concern.

The studies made for three years by Prof. Esmeralda Payão Dematée, to support thesis submitted to the horticultural Department of Federal University of São Paulo, concluded that coxim would be the ideal substitute for tree fern fiber. What is your opinion about ?

I haven't done yet enough experiences with the coxim but by the preliminary analyses I've done, I think it is a very poor in organic material and regarding to this point, it is closer to piassaba than to tree fern fiber.
I used it in some pots which rooted well. Rosário (from Quinta do Lago) has also succeeded with some pots, the roots were well established but we need four, five years to have a conclusion about.
As far as I am concerned, this thesis fell into a basic error. The major error is not to broach the humus acid. I think it is a little singular. Any book about vegetal nutrition gives an enormous importance to this matter, whole chapters and there are doctorate thesis developed on this subject. We can not considered this subject without analyzing the decomposition of the substrate. And when we analyze the decomposition of the substrate, we go into humus acid.
I saw some incredible things concerning the humus acid in Amazon region, it has really a great importance. It has unbelievable qualities.
The amount of humus acid in coxim is less than in tree fern fiber. The humus acid is one of the points of the cultivation but there are others like soluble salts, many kinds of salts, pH but, in my opinion it is the most important to be measured.
Don't have illusions about! A substrate which doesn't decompose, which lasts a whole life is a bad substrate.

According to the producer, in Recife, where the humidity level is high, it lasts for 4 years and, theoretically, in drier places, it could last more, 8 years perhaps.

May be, it is difficult to answer this question but if it lasts for 8 years, it is, for sure, a bad substrate.

So the big problems you see in coxim, would be the nutrition and lack of decomposition?

Any substrate must be a cellar. I am not against or in favor to coxim, I just don't have enough information to believe in and I consider all those statements about its qualities a temerity. I don't agree with those statements. All those things have never been controlled.
I repeat, I don't have experience with coxim but, when we think about substrate, we must think about supplying nutrients. We started our article about substrate(Orquidário bulletin, Vol. 11, n^o 1, Jan-Mars 1997): "The substrate, no doubt about, is the base of a good orchids cultivation. It is not only support but also source of nutrients for the plants, it should present basic and indispensable qualities like consistency as support, good ventilation at the roots, capacity of retaining water, without being soaked, adequate pH e, at last, the possibility of decomposing generating humus ( particularly humus acid) and providing plants with the mineral elements they need".
Coxim is a good support, has consistency, good aeration to the roots but concerning the capacity of retaining water, it is less than tree fern fiber.

Maria Esmeralda concluded her thesis informing that one of the inconveniences of coxim is low capacity of retaining humidity when it is new but ,according to the producer, coxim has been improved and nowadays the capacity of retaining humidity is better. Must we deduce that there is no substitute to tree fern fiber?

At least, I don't have.
To put in other way, you can have million but there is no universal substitute for tree fern fiber. If you hang an orchid in a tree, it grows well, if you put in peroba bark, it goes wonderfully well. You can have a plant which grows well in certain substrate and in some other, it doesn't. Some orchids grow well in piassaba. Another example, the sphagnum moss is great substrate, has a kind of antibiotic, decomposes very fast lasting less than tree fern fiber and. Trees bark rich in resin are bad because the resin doesn't allow the bacteria growth.
For example, I've done a mixture: wood, sphagnum moss, tree fern fiber and sand. Some plants grow very well but it can't be used for all.
I've never measured the humus acid level but it shouldn't be negligible because there is the decomposition of wood, sphagnum moss. There is açai'nut, the decay is too much fast, there is the natural coconut bark.

Sérgio Silva: For example, if you put a beautiful Maxillaria, very well rooted, in a natural coconut bark, the new root grows, beat the bark and dyes.

That's exactly I am saying! An universal substitute is difficult.
Do you know any orchid which doesn't go well in tree fern fiber? I don't.
You can say that it is not that well in tree fern fiber, it goes better in other substrate. But, finally, you can put every orchid in tree fern fiber and it will grow.
To reasoning in universal terms, for every kind of plant, not to referring to specific plant but for all, it is very hard, it doesn't exist yet.
For who runs a commercial nursery, the problem is serious.

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