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The scientific background to the "Leaf Colour Chart"

dw1305

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Hi all,
As a couple of people have asked about the <"leaf colour chart" (LCC)">, (that is linked into various threads talking about <"Amazon Frogbit and the "Duckweed Index">), I'll add some references into this thread, I'll add more as I collect them.

12-rice-leaf-color-chart.jpg


The LCC was developed to give <"Rice Farmers"> a visual indication of the nitrogen status of their crop.
The University of California, in collaboration with the California Rice Commission and the California Cooperative Rice Research Board, has released the UC Leaf Color Chart, version 2.0.

The ruler-like device contains eight color cells of varying shades of green that growers can use to gauge crop mid-season nitrogen levels and whether they need to topdress.

Originally introduced by UC Cooperative Extension farm adviser Cass Mutters in 2000, the Leaf Color Chart was recently revisited as a tool to be used in tandem with the UC publication, “Rice Nutrient Management in California,” to help rice growers address the state’s nitrogen management plan.
cheers Darrel
 

Oldguy

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I'll add more as I collect them.
Interesting chart & link. Any chance that the numerical scale on the back (not visible or stated in the link) could be printed on the front. My thinking is it could be a better bet for planted tanks than Nitrate test kits. I assume it would need a bit of experimentation to find an indicator plant to replace rice.
 

dw1305

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Hi all,
Any chance that the numerical scale on the back (not visible or stated in the link) could be printed on the front.
There is a numerical scale, but it doesn't give you any <"real empirical values">.

This is the original research (from Takebe & Yoneyama).

LCC_N_Values.JPG
My thinking is it could be a better bet for planted tanks than Nitrate test kits.
I think so, put at its most fundamental level the plants can't lie.

Because plants need more nitrogen (N) than the other mineral nutrients, and nitrogen is mobile within the plant, then small, pale older leaves are likely to indicate nitrogen deficiency.

There are some caveats, based on both <"Liebig's law of the minimum"> and other nutrient deficiencies that <"may cause pale leaves">.

Initially I'd expected to be able to recommend test kits and analytical methods that would work over the whole range of freshwater aquarium values, but it became apparent early on that there were some difficulties (particularly with nitrate (NO3-) measurement) and that a lot of reported nitrate values on forums etc were definitely wrong.

I was using <"biotic indices at work"> and it became apparent that they were actually a much more sensitive indicator than the water testing we were doing. We were also looking at <"phytoremediation using floating plants">, and this was very effective in tropical situations, from that starting point it just seemed an obvious step to combine the two approaches.
I assume it would need a bit of experimentation to find an indicator plant to replace rice.
Yes, it has to be a floating, or emergent, plant to take CO2 out of the equation. Not every tank can <"have an emergent plant">, so it had to be a floater.

After a bit of searching I found a floating plant that:
  1. Shows a linear response to nutrients,
  2. has a "leaf green" leaf,
  3. will grow in hard and soft water,
  4. persists in low nutrient situations,
  5. and that plant is my both my "Duckweed" and "Rice",
  6. <"Amazon Frogbit (Limnobium laevigatum)">.
This is what it looks like, if you <"feed it plenty">.

sigrjybcq-width-3264-height-2448-cropmode-none-jpg.jpg


Initially I focused on Lemna minor (hence the "Duckweed Index"), Eichornia crassipes, Salvinia "auriculata group" and Pistia stratiotes, because they were all plants that were being used for <"phytoremediation">.

None of them <"were ideal in the tank">, Pistia and Salvinia are hairy, and this hides their leaf colour. Eichornia is a <"turned up to 11"> plant, and Lemna isn't happy in very soft water and goes yellow however much nitrogen you supply.

cheers Darrel
 
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dw1305

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Hi all,
Another very helpful thread. It would be great if the different threads could be pulled together into a 'sticky definitive guide.
I have started collecting the references for a series of articles that cover the the ground mentioned in <"Bedside Aquarium">. It is going to depend a little bit on what happens at work, but I'm hoping to pull this together by Christmas.

cheers Darrel
 

Oldguy

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it has to be a floating, or emergent
Thank you for your response. Looking forward to your article. I have difficulty with floating plants, the surface current moves them to the front pane and they tend to become submersed and rot. Playing with riccia fluitans and greater duckweed in two different bucket ponds (both came in as hitch hikers and both doing well).

Have copied the 'Rice Index' for reference.

Never had any success with tropical frogbit but I am trying to grow the UK type in the garden pond.

Have a fancy to try trailing marginals anchored to the rear pane of the tank and have them 'float' on the surface.
 

Oldguy

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Location
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Have a look at @hydrophyte's threads. He (<"Devin Biggs">) isn't active on the forum any more, but I think his company ("Aqua Verdi - Riparium Supply") is still active in the states.
Many thanks for the above links. Had forgotten about suction cup planters.

Have made a start with wire mesh folded into a simple envelope hanging on the rear glass pane of the tank. Started planting with Riccia fluitans as a vertical carpet (wall paper?). Rotala indica and Creeping Jenny (Lysimachia nummularia). These are three plants that I had to hand. The intention is to compare the submerged Riccia with it floating. The Rotala and Lysimachia are sandwiched against plastic scouring non woven material so that they grow hydroponically. The Rotala is also in the tank anchored in the inert substrate for comparison. All early days.

We start our own lock down next week with the only through road in the village closed for resurfacing, though we can escape after teatime but must be back for breakfast. I think as an oldie I will just stay in.

 
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