Fertilizers for coir (coconut substrate)

[David_Sweden]

Hi. I would like to hear about your experiences and opinions about fertilizers for coir.

My go-to fertilizer if not coir is one that exists only in my country (Sweden), called "Blomstra", it is liquid, one component, developed by the Swedish agricultural university in 1950, and the guy I know of responsible for developing it (Tom Ericsson) has recommended to use it every watering (half dose) and that principle seems spread among other believable persons, like the American Orchid Society. But you should then know Sweden is full of peat and all potting soil has >90% peat, it is understood, persons like me who try coir are weird, and nobody uses bark at all ever.

But since I started using coir for most palms a few years ago, I thought I probably need a specific fertilizer. I found "Gold Label Nutrients, Coco A & Coco B" (2 separate bottles, not to be mixed until water has been added):

I used it until two weeks ago and it seems to work well. However a few months ago they changed to these black bottles:

The problem with this is that they changed the contents too, without any advice for old customers how to proceed. On the old bottle it says "NPK = 2-2-6 plus 2 MgO" but the new bottles have no such statement. And they state content on old bottles for the complete mix A+B but separately for the new bottles, which is not helpful, but there is e g much less N in the new version. The old version states content N/P2O5/K2O/MgO 6/2/8/2 weight%, to me it seems this doesn't match the "NPK = 2-2-6 plus 2 MgO" statement. The new bottles say for N/P/K 4.0/0.5/3.0 for A and 2.5/4.0/7.1 for B, so if mixing 1+1 I would that expect to result in the average i e N/P/K = 3.3/2.3/5.1. Quite confusing. Also I never was convinced 2 bottles are needed, and why does it say shake well, it is not needed for Blomstra. I asked the manufacturer but no reply. I asked where I bought it and they refer to a "Growing schedule":

This is when I decided to abandon Gold Label. If to follow this I would need to buy enzymes and 3 other bottles. I do not think that is needed and I am certainly not going to try it. 

Another brand readily available is Growth Technology (seems British but they have an American "sister company"). They too have a 2-component coir fertilizer "Alpha Coco" which I ignored.  I decided to buy "Ionic Coco Grow" (I found one of those annoying "growing schedules" for this too where they try to make me buy e g silicon.. but it was on a 3rd party site). The instructions say that I at every watering should check EC and pH (OMG!) which I of course won't do, I do own an EC meter and a good pH meter (most people don't since they are a bit expensive). I decided to use half dose (3.5mL/L) every watering. No shaking.

However they also have "Formulex", which seems to be recommended for everything including coir. If so, maybe I could just as well go back to "Blomstra"? Is a fertilizer made with peat based soil in mind also suitable for coir?

[happypalms]

One of the best mediums there is for growing and germinating palms coco coir substrate I use the PH buffered its amazing 

[David_Sweden]

I'm not sure I know what you mean. Even all peat based soils are pH balanced. And it says here that "The buffering capacity of a soil indicates the capacity of the soil to resist pH change." and "Soils with a high proportion of clay or organic matter have [better buffering capacity]" and that clay is better than loam which is better than sand - but I guess they focus on outdoors soil then. For potting soil I believe "dark peat" (what you in the US call "peat humus" which maybe you don't use much but here they usually have around 45% "peat humus" from sphagnum and 45% "normal sphagnum peat" in potting mixes) should be very competitive compared to clay (lots of small pores) and even also normal sphagnum peat. And I read that coir has even better capillarity, and high CEC (higher than peat). 

[David_Sweden]

I searched a bit on my own.. Someone in Palmtalk's forum says a difference between palm fertilizers and "normal fertilizers" is that palm fertilizers contain Manganese. Well Coco Grow contains manganese. And Formulex contains even more. And so does Blomstra. So from the perspective of containing all necessary substances it looks like they all are ok.

And an ovbious difference between peat moss and coir is that manufacturers add mineral fertilizer to peat moss based potting mixes (at least here in Sweden) but not to coir. But that only lasts a few weeks. And the dose is too high (about twice as much as I'd like) that's why I buy mix for seedlings if peat moss based.

Here is an interesting page that quotes a study made by a Chinese university. Seems to say there might be a difference in uptake individually for various nutrients (coir has highest uptake, especially P, K, and S), Mg uptake similar, accumulation of N/P/K/S higher in coir. It also says coir "Can hold on to magnesium and calcium, so fertilisation regime has to be adjusted".

I'm not sure how much this all matters. Both coir and peat moss seem to handle all nutrients well. In a perfect world the fertilizer has exactly the right proportions of each nutrient. If there is a difference in uptake that doesn't match the fertilizer proportions, and influence of different pH, well, of course I leach the pots 2-3 times per year, I'm thinking the plant consumes what it wants, the rest is left in the pot and flushed at the next leaching, the residue (the composition of salts) before leaching will differ, isn't that fine?

Than I found this university study, which mainly compares coir to what I think is a peat moss and perlite based mix ("Scotts MetroMix 220"). It says coir "is rich in potassium and the micronutrients Fe, Mn, Zn, and Cu. Due to the high potassium content of the media a reduction in potassium fertilization has been shown to produce beneficial results" and "However, some studies have shown that it is necessary to increase the nitrogen fertilization for coir grown plants to compensate for N immobilization of the media. Coir has a low Cation Exchange Capapcity (21-30 meq./L) so it does not retain cations or buffer against pH change well"

I'm surprised to read coir comes with any nutrients at all, and íf it does, surely it can't last many weeks anyway? But if to have any action based on this I guess it is to make sure the fertilizer has much N and little K at least. If so then both "Coco Grow" and "Formulex" fail. Blomstra does better since it at least has less K than N. Makes me think Blomstra is slightly better. But that I can use any one of these since the built-in nutrients in the potting mix surely can't last many weeks?

[PalmsandLiszt]

My understanding is that coir is not good at binding essential nutrients. Clay-based media are much better at this. I use a lot of coir, but always in combination with something clay-based and slow-release like osmocote. But the studies you have dug up are interesting.