Interesting study in fertilzer

[Joseia]

Originally Posted by Orchid Whisperer

This comment is useful . . . how?? Was there a reason for this meaningless snarky comment?

I found it humorlifical. But maybe because I am a fan of all things scientifical.

[naoki]

I would say it was a good small study and you can learn things from this study; they used a simple factorial design and the folliar analysis was detailed (most relevant minerals are included). I would say any scientific research is useful to progress our understanding. Some people (not you Estacion, but some republican administration) deny the evidences and logical thinking processes behind them since they simply don't understand or they are blinded by money. But accumulation of small clues from experiments lead us to general comprehension.

Th root:shoot ratio behaves in the expected way with this Cattleya hybrid (more fertilizer means more shoot, but not much root production).

Although they didn't give the detail of their statistical exploration, there were obviously strong interactions between mineral and organic fertilizer treatment. I was also very surprised by the large synergistic effect between inorganic and castor meal based organic fertilizer. It is even more surprising if you consider the amount of fertilizer they have applied. For Peters, they seem to be applying 1000ppm TDS (200ppmN) every week (calculated from Table 1). This is quite a bit more than what many of us has been using for orchids recently. The cause of this synergism needs to be further investigated, but it is very promising. BTW, I don't think that they said that organic is better than mineral fertilizer.

Then the foliar analysis was interesting, too. As you all know, what you give to orchids isn't same as what they assimilate even with mineral fertilizers. So foliar analysis is an useful tool to look at the overall picture. Some minerals are not influenced by availability, and others respond to fertilization. We don't know much about the sufficiency range in orchids, and this study gives a point data about the upper range of the boron content. B toxicity has been documented in other studies using manure. It is a good thing to know, and we should be careful.

[Ray]

Originally Posted by naoki

Then the foliar analysis was interesting, too. As you all know, what you give to orchids isn't same as what they assimilate even with mineral fertilizers. So foliar analysis is an useful tool to look at the overall picture. Some minerals are not influenced by availability, and others respond to fertilization. We don't know much about the sufficiency range in orchids, and this study gives a point data about the upper range of the boron content. B toxicity has been documented in other studies using manure. It is a good thing to know, and we should be careful.

Tissue analysis can be tricky to interpret. For example, there are some nutrient ions - notably K, and I think B - that are taken up as much as possible by the plants, whether they need it or not, so a high tissue content indicates more about what was available to the plant, rather than having any bearing on its needs.

[naoki]

I agree that tissue analysis can be misleading without sufficient knowledge of plant physiology (I won't claim I completely understand it). It is a composite of nutrients in the media, active/passive transportation from the media (or water surrounding the root) into plant roots, transportation from root to leaves, recycling rate (e.g. phloem mobility), rate of loss (e.g. leaking from leaf surface) etc. With isotope studies, people can see more detailed views of how minerals are moving.

At each step, different minerals can behave differently, and also different minerals can interfere each other.

We discussed the excess uptake of K in ST. But take a look at Table 4. The data doesn't contradict with it, but I wouldn't say they provide a STRONG support for this claim in this particular case. K isn't influenced dramatically by the external availability of K. With regard to the external K availability, (none, CaN) < (Ptr, Ptr+CaN) < (Ptr + organic). K concentration of none is slightly lower, but, beyond that I don't see dramatic increase in K. K is highly recycled element especially in epiphytes. So this might be the reason that K might be high even in no K treatment like CaN treatment. However, if the excessive K uptake is happening, I would expect more difference in the environment with high K, don't you? It is possible that K in organic fertilizer is not reaching to the root, but I speculate K should be relatively easy to leak out from dead plant if you consider how K is used in plants (and animals).

On the other hand, data might be showing some suggestion of K vs Ca antagonism.

[Ray]

I love this kind of discussion, but in years of studying, and with hearing many growers' observations and "takes" on their own studies and readings, I have concluded that there simply isn't enough actual, true knowledge about orchid nutrition to make me want to jump on another new approach. The variables are just too many to account for. That has led me, after forty years of orchid growing, to a different, much more practical approach:

Using whatever method you prefer to do so, choose a fertilizer formula that you think is “good,” whatever that means. Use it very sparingly, but consistently. Observe your plants through an extended time – six months is probably too short; maybe a year is better. If you see a problem that you know isn't due to other aspects of your culture, make a change and repeat the actions of my last sentences.

Fertilizer is an important, but very minor aspect of orchid culture. As I have heard others say here, in all likelihood, “applying more fertilizer is not going to fix any issue you are experiencing.” I will add a corollary that, if you're trying to get your plants to perform better, fertilizer is probably the last thing you should look at in your overall culture.

[Fernando]

I absolutely agree.

But unless this 'fertilizer is like medicine' - nonsense does not come to an end, people will continue to increase fertilizing in the hope that more 'food' will compensate for too low temperatures or for too low light or for weeks of oblivion ...

[bil]

Originally Posted by Fernando

I absolutely agree.

But unless this 'fertilizer is like medicine' - nonsense does not come to an end, people will continue to increase fertilizing in the hope that more 'food' will compensate for too low temperatures or for too low light or for weeks of oblivion ...

Preach it Brother!

[Leafmite]

I agree with Ray. It is important to observe one's plants and their reactions. Nutritional needs vary plant by plant and environment by environment. The water you are using for your plants as well as your medium will affect what nutrients you must add. Temperature and light have a role, as does stress. The adaptions of the species to survive in their native environment will affect what nutrition is needed. And, like people, plants can be individuals. Some plants grow faster than others due to their genetics and some grow slower. This affects what nutrients are needed. HOW you water will affect what nutrients are needed, too. If your pots get flushed very well by pouring rain or a hose every day, you may need to fertilize more often and keep in mind the nutrients that are more likely to be flushed from the pot and the ones less likely to be flushed.

This is why we all have so many different opinions on what works as a fertilizer.
I actually grow a few plants that have very sensitive roots and cannot tolerate the inorganic fertilizers...even slow release ones. I need to use a light dose of organic fertilizer for these. Then there are the CP's that catch their own nutrients. They make life easy.

[Fernando]

Originally Posted by bil

Preach it Brother!

Sorry, agnostic over here!