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Testing nitrate and po4
- Thread starter jwmachon
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Hi all,
Estimative Index (EI) was designed so that the level of mineral nutrients always exceeded the plants minimum requirement and growth was dependent upon CO2 level and PAR.
The Duckweed Index idea is that you use the growth and leaf colour of a floating plant (originally "Lesser Duckweed" (Lemna minor) & subsequently "Amazon Frogbit" (Limnobium laevigatum)) to keep your plants in the <"goldilocks zone"> where the availability of <"Liebig's limiting nutrient"> never stops plant growth. It needs to be a plant with <"Diana Walstad's aerial advantage"> to take CO2 out of the equation.
Have a look at the <"The scientific background to the "Leaf Colour Chart""> for a bit more explanation about using your plants to indicate nutrient status.
In terms of test kits, nitrate (NO3-) is <"particularly problematic"> to test for in freshwater, it is actually easier in seawater because of the <"known number of chloride ions"> and a datum value you are aiming for. If you were really keen on knowing the NO3- value then an <"ion selective electrode"> is probably the way forward.
<"Phosphate (PO4---) is easier to test for">, and <"I'm told"> that the JBL sensitive (low range) test kit is fairly good. Because I use a <"horticultural fertiliser">, and <"I'm not looking for optimal growth">, I'm not aware that I've ever suffered from PO4--- deficiency.
A good thing about both nitrate and phosphate is that they are highly mobile within the plant, which means you get a <"pretty instant growth response"> when you add them, if they were deficient.
cheers Darrel
The rationale behind both <"Estimative and Duckweed Indices"> was that you wouldn't need to test the water.
Estimative Index (EI) was designed so that the level of mineral nutrients always exceeded the plants minimum requirement and growth was dependent upon CO2 level and PAR.
The Duckweed Index idea is that you use the growth and leaf colour of a floating plant (originally "Lesser Duckweed" (Lemna minor) & subsequently "Amazon Frogbit" (Limnobium laevigatum)) to keep your plants in the <"goldilocks zone"> where the availability of <"Liebig's limiting nutrient"> never stops plant growth. It needs to be a plant with <"Diana Walstad's aerial advantage"> to take CO2 out of the equation.
Have a look at the <"The scientific background to the "Leaf Colour Chart""> for a bit more explanation about using your plants to indicate nutrient status.
In terms of test kits, nitrate (NO3-) is <"particularly problematic"> to test for in freshwater, it is actually easier in seawater because of the <"known number of chloride ions"> and a datum value you are aiming for. If you were really keen on knowing the NO3- value then an <"ion selective electrode"> is probably the way forward.
<"Phosphate (PO4---) is easier to test for">, and <"I'm told"> that the JBL sensitive (low range) test kit is fairly good. Because I use a <"horticultural fertiliser">, and <"I'm not looking for optimal growth">, I'm not aware that I've ever suffered from PO4--- deficiency.
A good thing about both nitrate and phosphate is that they are highly mobile within the plant, which means you get a <"pretty instant growth response"> when you add them, if they were deficient.
cheers Darrel
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