Air movement improves orchid nutrition

[K-Sci]

Originally Posted by rbarata

I haven't confirmed but common sense tells me that the evaporation rate under an air flow 90% RH is different from an air flow 60% RH, and so on.
This means, the higher the humidity the less important is evaporation in the equation.

Without question. The implication is that a RH that is too high may reduce nutrient uptake at the roots. I've never heard this or seen studies, but it would follow.

Adding to this, air doesn't have any nutrient in its content. It might be present in the water droplets but for that to happen, without any artificial device (mister or similar), RH must be at almost 100%.

I agree that the air itself doesn't deliver nutrients. I'm not sure what the point is here, however.

If you think this doesn't add anything valuable to the discussion, that means I haven't understood the original post.

The first part of your post makes sense, but the second part doesn't seem to be addressing the post, so maybe I wasn't terribly clear in the original post.

All my original post says is that that higher airflow causes higher transpiration. Water lost via transpiration must be replaced by water taken in by the roots. That water would have nutrients in it. Therefore, increasing airflow would should result in more nutrients brought into the plant via its roots.

Thanks for your post!

-Keith

---------- Post added at 02:54 PM ---------- Previous post was at 02:32 PM ----------

Originally Posted by Roberta

I sense here an attempt to "micromanage" the orchid growing process. All of the factors are interrelated, so for good growth, they just need the basics - light, air, temperature, water in the correct amounts. A small amount of fertilizer, but the details not all that important, The rest takes care of itself. Tweaking one factor in the absence of the others is not going to make miracles. There aren't any magic potions.

Providing orchids with good air movement is often described as a horticultural requirement for fungal and bacterial disease prevention. I'm not sure how having another reason would be micromanaging.

-Keith

[Roberta]

Air movement is certainly important - to prevent disease, also to provide the wet-dry cycle that most epiphyitic orchids need (to various degrees) As a factor in nutrition to be managed, that's the micro-managing part. I would consider the variation in amount of nutrition to be a miniscule fraction of the benefits of air movement, which overall is VERY important. But then, I consider nutrition in general to be a relatively minor factor in orchid culture, for the vast majority of orchid types. Other parameters are far more important. Get the other factors correct, then the details of fertilizer may make a difference.

[rbarata]

*Therefore, increasing airflow would should result in more nutrients brought into the plant via its roots.

Not quite right, IMO. If the air flow has a high humidity, the plant would have a lower transpiration rate, which means less water is need to be absorbed. So, less nutrients.
This is a very simplistic view but I think it's correct.

[estación seca]

I remember asking my bio professor about humidity and transpiration. He said even at 100% relative humidity, transpiration still occurs. He said that if this were not the case, because non-woody plants are held vertical by water pressure, those soft plants would flop over every time it rained. But they don't.

[rbarata]

A good reading.

[K-Sci]

Originally Posted by Roberta

I consider nutrition in general to be a relatively minor factor in orchid culture, for the vast majority of orchid types.

How about posting some current flower photos to prove it. That is what we grow orchid for, isn't it. -Keith

---------- Post added at 08:15 PM ---------- Previous post was at 08:06 PM ----------

Originally Posted by rbarata

Not quite right, IMO. If the air flow has a high humidity, the plant would have a lower transpiration rate, which means less water is need to be absorbed. So, less nutrients.
This is a very simplistic view but I think it's correct.

Wouldn't growing orchids at 100% RH for any period of time result in fatalities due to disease?

-Keith

[Roberta]

Originally Posted by K-Sci

How about posting some current flower photos to prove it. That is what we grow orchid for, isn't it. -Keith[COLOR="Silver"]

Plenty of recent pix on the Southern California Orchid Species blog (link in my signature)... My section is a little sparse for the current month only because I couldn't get out out the yard to take a lot of photos due to health issues. I also have pretty much the same collection of L. anceps and relatives as my cohort on the blog, not a lot of point in repeating them (It's L anceps season...). And as I have stated often before, I fertilize very lightly when I get around to it. And in prior months, many, many more blooming species - all current for the month prior to each page. So enjoy... Not enough hours in the day to post the same photos in multiple places just for bragging rights.

[SouthPark]

Originally Posted by Roberta

Air movement is certainly important - to prevent disease, also to provide the wet-dry cycle that most epiphyitic orchids need (to various degrees).

I totally agree with that. I took these pics this afternoon - new years day in Australia. These plants (Angcm. eburneum and Den. discolor) generally get the nice natural air-flow --- and are very sun-hardened. These have been absolutely zero maintenance - except for needing to water them - which is done with the automatic 'hunter' pop-up lawn sprinklers, which also waters the lawn grass at the same time.

They have never been attacked by mealybugs or scale or anything for a few decades. Never got any disease such as fungal attacks or bacterial rot etc. These plants seem to be 'right at home' and having a great time out there. They withstand big rains, and searing heat, intense sunlight etc.

And no manual fertilising of any kind ever done for these ones. Still growing in their original pots of scoria. Never repotted heheh ----- so a lot of the plants are actually hanging outside of the pots.

Pic 1

This other pic is also a eburneum - just growing nicely under something ------ zero maintenance as well. No manual fertiliser. They really probably don't need much - as Roberta mentioned.

Pic 2

[Shadeflower]

Originally Posted by Ray

How do you know they are absorbing less nutrition?

Sorry Ray I missed your question.

So I will give an example I had this winter. A phal for whatever reason was not growing well, I discovered in hindsight the ph was too low so that was probably why.

I was watering it and fertiling it like all other orchids but the ph was off so I presume the plant was not able to absorb nutrients as well. Now I only fertilize up to 180ppm in general maximum.

When I checked on the orchid after a few months of something not being right the ppm in the pot was 435ppm.

Now I'd only ever watered it up to a maximum of 180ppm but because the plant was still drinking water but clearly not the nutrients they were building up in the pot over time. I had never ever watered with that high a solution but if the plant only absorbs water and leaves the nutrients behind then over time they build up and would require flushing out of the pot.

I have read that plants can influence through chemical reactions in their cells which nutrients specifically to absorb.
I have it bookmarked somewhere but to find it would require reading through endless articles.... Maybe I will stumble across it again, I do think I remember which article it was, I will have a look to see if I can find it.

Anyway yes nutrients get locked out by other nutrients.
In the same way mine were getting locked out by a too low ph and the plant wasn't able to absorb them (like if they hadn't even been in the pot) but if a plant is receiving too much of one nutrient that it doesn't need as much of then it can through chemical reactions in the cells influence how much of it it absorbs. This is what I have read about it but that is all I know.

just a quick google search comes up with a good explanation on the matter of nutrient uptake: Plant-Soil Interactions: Nutrient Uptake | Learn Science at Scitable

So to bring this on topic, if a plant transpires more through more air flow it needs more water than a plant that is not transpiring as much. As such a plant that is transpiring more, either in hot weather or from a fan could benefit from more plain water in between watering's (since it is transpiring more water). Adding the same amount of fertilizer would not mean the plant would absorb more, it will absorb what it needs but if the nutrients build up in the pot as a result (more water getting absorbed in relation to the nutrients fed) then the nutrients can build up and cause root burn in the pot. So imo with enough plain watering's to compensate for a plant transpiring more should be absolutely fine.

In any situation it's about seeing how much a plant needs. Either a bit more or a bit less. Maybe this would explain why some gardeners need to use a bit less or more fertilizer and it is never the same depending on the different climates they are grown in.

[Ray]

To me, what you describe sounds like typical mineral buildup - a result of evaporation - not necessarily slowed nutrient uptake. That might also be the case, but using the accumulation as evidence of slowed uptake is “iffy”, at best.

Back to Roberta’s comment about nutrition being of relatively low importance, I totally agree. Naoki Takebayashi, a professor at University of Alaska - Anchorage, once did the calculations for the chemical reactions that fix carbon within a plant (i.e., “growth”), and for any plant to add one pound (454 g), it must absorb and process about 200 pounds (~91 kg) of water, but only 0.01 pound (~5 g) of nutrients.

So how long does it take for a plant to add a pound of mass? Corn (maize) in the middle of summer, maybe a week or two. A tiny lepanthes probably won’t add a pound of mass in a century. A paph? 4 years?