# The scientific background to the  "Leaf Colour Chart"



## dw1305

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.






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.



Takebe, M. &  Yoneyama, T. (1989) <"Measurement of leaf color scores and its implication to nitrogen nutrition of rice plants">_Japan Agricultural Research Quarterly_ .
Ali,M, Al-Ani, A., Eamus D. & Tan, D. (2017) <"Leaf nitrogen determination using non-destructive techniques–A review">, _Journal of Plant Nutrition_, *40*:7, 928-953.
cheers Darrel


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## Oldguy

dw1305 said:


> 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.


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## dw1305

Hi all, 





Oldguy said:


> 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).






Oldguy said:


> 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.





Oldguy said:


> 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:

Shows a linear response to nutrients,
has a "leaf green" leaf,
will grow in hard and soft water,
persists in low nutrient situations,
and that plant is my both my "Duckweed" and "Rice", 
<"*Amazon Frogbit (Limnobium laevigatum)*">.
This is what it looks like, if you <"feed it plenty">.





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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## Onoma1

Another very helpful thread.  It would be great if the different threads could be pulled together into a 'sticky definitive guide.


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## dw1305

Hi all, 





Onoma1 said:


> 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


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## Andy Taylor

dw1305 said:


> Hi all, 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


Looking forward to it.


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## Oldguy

dw1305 said:


> 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.


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## dw1305

Hi all, 





Oldguy said:


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


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.

cheers Darrel


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## Oldguy

dw1305 said:


> 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 R*iccia *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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## dw1305

Hi all,
I was <"sent these the other day"> (they were on some web pages that I wrote ~20 years ago, and which are no longer accessible for me).  They aren't strictly aquarium related, because the trial plants are Radishes, but they were grown hydroponically and it does show the effects of very elevated levels of nitrogen (if you want to convert to the N values to NO3, multiply by them by ~4.4). Everything else is the same, it is just the nitrogen level that differs.  










7ppm (mg/L) N (~31 ppm NO3)




112 ppm N




336 ppm N




556 ppm N




896 ppm N

cheers Darrel


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## X3NiTH

That’s a liberal dose of Manganese compared to the Iron level, was there any reasoning behind the decision to use this level or is that just a result of the analysis of content of the Micronutrient you used? 

I thought I was being liberal using 0.05ppm of Mn to 0.15ppm Fe per dose, Now wondering if I am being too conservative in its addition.


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## dw1305

Hi all,


X3NiTH said:


> was there any reasoning behind the decision to use this level


I used to make up the micronutrient solutions from scratch, so I'd guess it was the level  from the "selected recipe", which was probably <"Long Ashton Solution">, but I can't actually remember. 

cheers Darrel


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## X3NiTH

Snipped from this Paper - Comparison of Nutrient Solutions for Growth of Plants in Sand Culture


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## X3NiTH

Darrel I think the value you have for Mn in your documentation is an order of Magnitude too high compared to the Long Ashton Recipe above, typo?


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## dw1305

Hi all,





X3NiTH said:


> Darrel I think the value you have for Mn in your documentation is an order of Magnitude too high compared to the Long Ashton Recipe above, typo?


Either a typo, or I made it up wrong at the time. No way of knowing now, but my guess is that it is the latter.

Cheers Darrel


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## Cédric

dw1305 said:


> After a bit of searching I found a floating plant that:
> 
> Shows a linear response to nutrients


Hi Darrel,
I'm wondering what is the "linear response" of Frogbit you mentioned. I join a picture of healthy Frogbits that even become "arborescent" under good conditions.


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## dw1305

Hi all,


Cédric said:


> I'm wondering what is the "linear response" of Frogbit you mentioned. I join a picture of healthy Frogbits that even become "arborescent" under good conditions.


They look good. Have they rooted into the substrate?

When they are really enjoying themselves, and are <"beginning to become crowded">, they will often produce <"these aerial leaves and flower">.

If you feed the<"water column plenty">, and they aren't crowded, they tend to look more like these - <"Frogbit envy"> & <"Do we really need that much fertiliser ?">.

A combination of <"over-crowding, tropical sunlight and plenty of nutrients"> gives you this.






cheers Darrel


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## Cédric

dw1305 said:


> They look good. Have they rooted into the substrate?


They haven't yet. Plenty nutrients + 90% humidity in the air.


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## Cédric

dw1305 said:


> A combination of <"over-crowding, tropical sunlight and plenty of nutrients"> gives you this.


Hopefully we miss tropical sunlight over there  Too big for 240 liters tank.


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## plantnoobdude

Cédric said:


> Hopefully we miss tropical sunlight over there  Too big for 240 liters tank.
> View attachment 198506


Is that…. Frogbit……?


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## Cédric

plantnoobdude said:


> Is that…. Frogbit……?


Hi plantnoobdude,
Absolutely, Frogbit. Tell you if everything is ok in the tank (nutrients). But when all is ok, you have sometimes to get them out the tank


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## dw1305

Hi all,


Cédric said:


> Hopefully we miss tropical sunlight over there  Too big for 240 liters tank.


That is <"pretty impressive">, and shows the plasticity in growth form that Amazon Frogbit (_Limnobium laevigatum)_ can exhibit.

That is one of the real advantages of _L. laevigatum_  for the <"Duckweed Index">, it has the potential to get very large, very quickly, but isn't a <"_turned up to eleven_"> plant like _Eichornia crassipes (_or, to some degree, _Pistia stratiotes). _

One reason that <"it can grow quickly"> is that _Limnobium laevigatum _has leaves which are structured a bit like bubble wrap, basically very little plant material surrounding an air filled space, with the water providing most of the structural support.

TS section through a Frogbit leaf, showing the structure of the large, spongy, aerenchyma cells.







_Lemna minor _also gets <"bigger with more nutrients">, but not as dramatically, it mainly shows an <"increase in vegetative propagation">.

When _L. laevigatum_ is running on <"petrol fumes">,  that is ,

enough photosynthetically active / usable radiation  (P A /U R) to get above <"light compensation point (LCP)">,
all nutrients present, but in very small amount,  and
<"access to atmospheric"> (<"~415 ppm">) CO2,
It  forms a perfect small plant, often with leaves only pound / euro coin sized, add then just add in more of everything? And you get @Cédric's plant.

This gives you a bit of an idea, you can see there wasn't really enough light & / or nutrients for the _Pistia, _and the water was also a  bit soft for the _Lemna minor_ (it is slightly yellow), but _L. laevigatum_ (& _Salvinia auriculata) _were fine, just small. This is a 60 x 30 cm tank with 2 x 24W T5 lights and water at about 120 microS, so not many ions of any description.





cheers Darrel


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## Cédric

dw1305 said:


> That is one of the real advantages of _L. laevigatum_ for the <"Duckweed Index">, it has the potential to very large, very quickly, but isn't a <"_turned up to eleven_"> plant like _Eichornia crassipes (_or, to some degree, _Pistia stratiotes)._


Hi Darrel,
I'm wondering what "turned up to eleven plant" means !??! I'm sure it's pretty simple to understand but I'm lost with the translation and the links didn't help (obvious I don't speak english very well). May you please explain in few words ?


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## dw1305

Hi all,


Cédric said:


> Hi Darrel,
> I'm wondering what "turned up to eleven plant" means !??! I'm sure it's pretty simple to understand but I'm lost with the translation and the links didn't help (obvious I don't speak english very well). May you please explain in few words ?


Apologies, it just means a plant that needs a lot of everything, light, heat, nutrients etc.

lt is from the <"film "Spinal Tap">, where one of the characters had an amplifier that goes up to eleven, and that makes it louder than all the other amplifiers, because they only go up to ten.

Cheers Darrel


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## Cédric

dw1305 said:


> lt is from the film "Spinal Tap", where one of the characters had an amplifier that goes up to eleven, and that makes it louder than all the other amplifiers, because they only go up to ten.


Hahaha....Of course....Spinal tape. I know that film very well and I see the scene you are talking about...So absurd...so hilarous...I can't forget the elves dancing around the poorly sized model of the dolmen on the stage. I didn't realize for a second that you were referring to that film. Very clear now. Thanks a lot.


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