Urea fertilizer - outstanding results
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Here is an exert from a publication by Alabama A&M and Auburn Universities "Fertilizing Greenhouse Crops in Alabama"
"Normally, nitrifying bacteria in the soil convert ammonium and urea to nitrate, but the optimum pH for these bacteria is about 7.0. In soilless media where the pH is usually 6.0 and below, these bacteria may be less active. The bacteria are also much less active when the potting media is cool (less than 60 degrees F). In addition, high ammonium can contribute to stretching of plants under winter conditions. The availability of nitrate nitrogen to plant roots is not linked as strongly to media temperature or bacterial activity".
Pay attention to the last sentence... "The availability of nitrate nitrogen to plant roots is not linked as strongly to media temperature or
bacterial activity". In other words the benefit of UREA is sensitive to temperature and pH and so are the potential problems.
"Normally, nitrifying bacteria in the soil convert ammonium and urea to nitrate, but the optimum pH for these bacteria is about 7.0. In soilless media where the pH is usually 6.0 and below, these bacteria may be less active. The bacteria are also much less active when the potting media is cool (less than 60 degrees F). In addition, high ammonium can contribute to stretching of plants under winter conditions. The availability of nitrate nitrogen to plant roots is not linked as strongly to media temperature or bacterial activity".
Pay attention to the last sentence... "The availability of nitrate nitrogen to plant roots is not linked as strongly to media temperature or
bacterial activity". In other words the benefit of UREA is sensitive to temperature and pH and so are the potential problems.
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...for terrestrial plants.
From Texas A&M....
Urea must first be converted to ammonia before it can be used by the plant. This conversion is dependent on the enzyme urease. Urease is another compound that is effected by factors such as temperature, moisture, etc.
Under cool temperatures urease is often rendered inactive and little, if any, N is available for plant growth.
Urea must first be converted to ammonia before it can be used by the plant. This conversion is dependent on the enzyme urease. Urease is another compound that is effected by factors such as temperature, moisture, etc.
Under cool temperatures urease is often rendered inactive and little, if any, N is available for plant growth.
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From the university of Hawaii Extension Service.....
"Toxicity symptoms (nitrogen): Plants are stunted, deep
green in color, and secondary shoot development is poor.
High N causes vegetative bud formation instead of
reproductive bud formation.
Toxicity symptoms (ammonium): Roots turn brown and
appear unhealthy, with necrotic root tips; plant growth
is decreased; necrotic lesions occur on stems and leaves;
vascular browning often occurs in stems and roots; severe
chlorosis and stunting of new leaves are symptoms
on some plants.
Ammonium toxicity is common in soilless media,
in highly acidic media, and under low temperatures. High
carbohydrate and potassium levels in the plant can prevent
some of the toxicity symptoms in some plants.
Ammonium fertilizers tend to make the soil more acidic,
and nitrate fertilizers tend to make the soil more alkaline."
"Toxicity symptoms (nitrogen): Plants are stunted, deep
green in color, and secondary shoot development is poor.
High N causes vegetative bud formation instead of
reproductive bud formation.
Toxicity symptoms (ammonium): Roots turn brown and
appear unhealthy, with necrotic root tips; plant growth
is decreased; necrotic lesions occur on stems and leaves;
vascular browning often occurs in stems and roots; severe
chlorosis and stunting of new leaves are symptoms
on some plants.
Ammonium toxicity is common in soilless media,
in highly acidic media, and under low temperatures. High
carbohydrate and potassium levels in the plant can prevent
some of the toxicity symptoms in some plants.
Ammonium fertilizers tend to make the soil more acidic,
and nitrate fertilizers tend to make the soil more alkaline."
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Stone
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Stone
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Stone
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Stone
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Stone
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All true and all irrelevent as I mentioned
Ummm one more.... this one is from Canada.
NH4+ toxicity in higher plants: a critical review
Based on this review it seems very risky to use UREA as the main nitrogen source when potassium levels are low.
NH4+ toxicity in higher plants: a critical review
Based on this review it seems very risky to use UREA as the main nitrogen source when potassium levels are low.
Stone
Well-Known Member
So give more K then
No, wrong again, use nitrate nitrogen is the correct solution.
Mike, read the research data. You like to trust in published data, I'm providing published proof why UREA is not a good choice of nitrogen source for orchids.
Low K can aggravate the problem but giving more K does not solve the problem. I mention the potassium because as Tyrone pointed out the UREA based fertilizer discussed here is 14:1:1 (very low K). K-lite is formulated using nitrates to avoid the ammonia toxicity issue.
Problem solved, we can use the official leaf color chart. :evil:
From my perspective the middle green shades are the ideal leaf color. That is green with a shift toward yellow rather than toward blue. :rollhappy:
From my perspective the middle green shades are the ideal leaf color. That is green with a shift toward yellow rather than toward blue. :rollhappy:
SlipperFan
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Interesting, Lance.
paphioland
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I'm sorry but this thread is hilarious.
Stone
Well-Known Member
Wrong again! Aquasol has 60% lower K than N (NPK – 23: 3.95 : 14)
and all N is not from UREA. Get your facts straight.
It may not be the best, use it with discretion?
A warning the manufacture gives....
"DO NOT USE AT TEMP HIGHER THAN 30 degrees!"
(They don't say why)
That lets me out, I need to fertilize when temps are higher than 30. And what happens if I apply it when the temp is 28 and then it goes up to 34? Is that because the UREA might damage my plants roots?
Who's arguing? I provided published proof and you provide nothing... that's not an argument. Show some published proof that UREA is better than nitrates so we can have a valid discussion that benifits the ST forum.
You say... "It may not be the best but it works and works well if used with discrestion".
I say.... why not look for a better solution and grow better plants without having to use discretion?
Stone
Well-Known Member
Thank you for the thread... lol
Now, I know what makes the big difference in my waterings: I always water at pH=7 (using ammonnitrate based fertilizer + rain water, or pure municipal water). So no toxicity at all, and every single plant is growing roots and leaves, even the small seedlings that were in the same pot for years with no evolution or plants considered as hard to grow (adductum, anitum, some albino forms...)
Now, I know what makes the big difference in my waterings: I always water at pH=7 (using ammonnitrate based fertilizer + rain water, or pure municipal water). So no toxicity at all, and every single plant is growing roots and leaves, even the small seedlings that were in the same pot for years with no evolution or plants considered as hard to grow (adductum, anitum, some albino forms...)
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