Lack of moisture on the surface of the pot with lecca

[Georg Luiz Barth]

Guys, I would like to know if there are any news on this subject, aiming to reduce the drying of the lecca in the upper layers of the semi hidroponic pot .....maybe by using glass wool, rock wool cubes, glass balls or even sphagnum. ... I appreciate the comments.

[estación seca]

You've previously mentioned you water every 2-3 days. My experience with S/H in a low humidity situation is that the plants are fine with that watering frequency if the roots extend down into the moist zone.

When I transplant small plants into S/H and their roots do not reach the moist zone, they do struggle unless I do something else. Spraying those tiny plants with a spray bottle frequently does work but takes a lot of time. I have put a layer of sphagnum on top of the LECA and kept that moist until the roots grow down into the LECA.

Ray has described using a thin circular plastic disc to set on top of the LECA, with a hole cut out for the plant. Other people here have described mixing rock wool cubes with the LECA, and some arrange it carefully so there will be a column of rock wool to the surface.

[Georg Luiz Barth]

Yes...one of the reasons, among many others, to do the watering every other day is this....try to keep lecca column with a certain degree of balance in humidity. The idea of using a plastic disk with a properly sized hole in the middle to fit around the orchid is impractical for me, as the thick phalaenopsis roots sprout in different directions and different heights.

[Ray]

There will always be a gradient of moisture - saturated at the bottom, less so as you move up in the column of medium. The greater your ambient humidity, the less the gradient.

I have been experimenting with rock wool cubes as a means of providing "wet spots" in the column, and it seems to work pretty well, although I've not yet decided if a "mix" or "layers" is a better idea. Certainly a "top dressing" of wet rock wool provides a bit of an evaporation barrier.

[BobcatJohnson]

Many people, including me, use a layer of small rocks to cover the top of the leca. The theory being that the rocks will slow the evaporation rate on the top of the leca surface, allowing the top layer to retain moisture by not drying so quickly. By using small rocks it is easy to remove them one at a time as new growths cause the base of the plant to spread. I still mist the top with R.O. water every morning, but the top of the leca rarely goes completely dry.

[Georg Luiz Barth]

Originally Posted by Ray

There will always be a gradient of moisture - saturated at the bottom, less so as you move up in the column of medium. The greater your ambient humidity, the less the gradient.

I have been experimenting with rock wool cubes as a means of providing "wet spots" in the column, and it seems to work pretty well, although I've not yet decided if a "mix" or "layers" is a better idea. Certainly a "top dressing" of wet rock wool provides a bit of an evaporation barrier.

Yes Ray...searching here on the forum, I found a post about Rockwool Medium, where you and other colleagues comment positive experiences on the subject. I found it fascinating... One question, using rockwool mixed with Leca, should I continue using 25ppmN watering every other day?

---------- Post added at 06:44 PM ---------- Previous post was at 06:36 PM ----------

Originally Posted by BobcatJohnson

Many people, including me, use a layer of small rocks to cover the top of the leca. The theory being that the rocks will slow the evaporation rate on the top of the leca surface, allowing the top layer to retain moisture by not drying so quickly. By using small rocks it is easy to remove them one at a time as new growths cause the base of the plant to spread. I still mist the top with R.O. water every morning, but the top of the leca rarely goes completely dry.

Thanks for the comments. I will consider them.

[Ray]

Originally Posted by Georg Luiz Barth

One question, using rockwool mixed with Leca, should I continue using 25ppmN watering every other day?

If you are maintaining a liquid reservoir, yes. I know some folks who go even more dilute...

The grower who co-developed K-Lite fertilizer, for example, feeds daily @ 5 ppm N.

[Georg Luiz Barth]

Originally Posted by Ray

If you are maintaining a liquid reservoir, yes. I know some folks who go even more dilute...

The grower who co-developed K-Lite fertilizer, for example, feeds daily @ 5 ppm N.

Thanks for the answer. I just purchased two rockwool bricks here in my town. We have several vegetable producers here, who adopt the hydroponic process and use rock wool bricks to grow seedlings. I soaked the bricks in tap water (TDS 30 ppm) pre-adjusting the ph to 6 with phosphoric acid and will keep them that way for 24 hours. After that time, I will repeat the procedure and check the PH fluctuation. The initial idea would be to replace the top layer of Leca with 1 cubic centimeter cubes, which will be cut from the original brick. I will be careful in the geometric distribution of the cubes, avoiding touching them face to face, to maintain good air circulation. The idea would be to keep my irrigation and fertilization system (already mentioned in a previous topic) in this new configuration.... excluding the routine of spraying a little water on the surface of the pot, which had the objective of minimizing the dry line of the pot.

[Ray]

Originally Posted by Georg Luiz Barth

I soaked the bricks in tap water (TDS 30 ppm) pre-adjusting the ph to 6 with phosphoric acid and will keep them that way for 24 hours. After that time, I will repeat the procedure and check the PH fluctuation.

Acid passivation is a surface phenomenon only and unfortunately, will not last, as the alkaline ingredients in the basalt will slowly overtake the acid treatment, especially if kept wet..

[estación seca]

The reservoir and always-moist LECA develop a flora of microorganisms that actively metabolizes and maintains the pH. The buffering capacity will be high compared to any salt solution your pour through.

I don't think you need to be at all careful with the arrangement of the cubes. Substantial air exchange occurs through small openings.