I've seen a couple of threads here and there about folks buying KNO3 from ebay and other internet sources and later getting BGA or other Nitrogen related deficiencies. It's now clear to me that some sellers may be sending out non-Potassium Nitrate products such as Calcium Nitrate or Magnesium Nitrate.
Although these are legitimate Nitrate containing salts, you should get what you are paying for. KNO3 is the best widely available Nitrate compound. The reason is simple - by weight and (atomic ratio), no other salt produces a high percentage of NO3 in the water column at very low toxicity. Ammonium Nitrate produces a higher NO3 concentration per teaspoon, and a higher Nitrogen content overall, but not without the toxicity issues.
The reasons for KNO3 superiority is obvious when you look at the weight ratio of NO3 in these products:
NO3 by itself weighs about 62 grams per mole.
Potassium Nitrate
(KNO3) weighs about 100 gram per mole, therefore NO3 is roughly 60% by weight of Nitrate.
Magnesium Nitrate
Ordinarily would have the formula Mg(NO3)2 but is typically sold in it's hydrated form Mg(NO3)2·6H2O (Magnesium Nitrate Hexahydrate 256 grams per mole) which lowers the percentage of Nitrate from 40% to about 24%. If someone sends you this product instead of KNO3 then you need to dose about 3X as much to get the same target Nitrate concentration that you would ordinarily get by dosing KNO3.
Calcium Nitrate
A similar story here. Ordinarily it has the formula Ca(NO3)2 but is typically sold in it's hydrated form Ca(NO3)2.4H2O (Calcium Nitrate Tetrahydrate 236 grams per mole) which lowers it's Nitrate content to about 53%.
Ammonium Nitrate
This is a completely different ballgame. Highly potent, use with care. This salt (NH4NO3) weighs a mere 80 grams per mole and is a Nitrogen superhero. Not only does it produce a whopping 74% Nitrate concentration, but the cation NH4 is also roughly composed of 78% Nitrogen. This is why most fertilizers, especially the terrestrial versions like Miracle Grow, derive at least some of their Nitrogen source via this salt.
Sodium Nitrate
While NaNO3 delivers a highly efficient 84% Nitrate concentration, Sodium, generally is very bad for plants and for most fish. So this salt should be avoided unless there are simply no other alternatives available at your location. It's efficiency at delivering NO3 however is good enough that depending on your lighting you might be able to use it effectively. It's also about 50% less soluble than Calcium Nitrate.
If you paid money for KNO3 then you need to ensure that it's what you got. I'll borrow the image from the EI tutorial. KNO3 is at the top of the image. You can see that it has a tendency to clump. Potassium Phosphate is shown in the middle of the image. You can see the difference in colour between the two salts. The Nitrate has a very slight yellow tinge in comparison. Also, most importantly, KNO3 has a funky, almost blue cheese odour to it, making it unmistakeable. Do not get fooled. If it does not have these characteristics then there is a strong probability that it is one of the other salts discussed above. This can easily explain why we have Nitrogen related difficulties.
EDIT: It should be noted that highly reputable sources of plant nutrients such as all of our sponsors, as well as garden centres such as Gardens Direct, have Quality Assurance measures in place to help ensure the integrity of their KNO3 and other dry powders. However, many anonymous internet trading sources do not. The mix ups may not even be intentional, as the vendor themselves may have been duped or they may not have systems in place to reduce the possibility of errors. Since almost all the various powders look very similar, i.e. all white powders, it is not surprising that mix ups can occur with identification, labelling , or shipping. Since we all know that Nitrate and Phosphate test kits are rubbish, then these are not reliable methods of determining which powder is which.
Top to bottom: KNO3, KH2PO4, Trace mix:
Cheers,
Although these are legitimate Nitrate containing salts, you should get what you are paying for. KNO3 is the best widely available Nitrate compound. The reason is simple - by weight and (atomic ratio), no other salt produces a high percentage of NO3 in the water column at very low toxicity. Ammonium Nitrate produces a higher NO3 concentration per teaspoon, and a higher Nitrogen content overall, but not without the toxicity issues.
The reasons for KNO3 superiority is obvious when you look at the weight ratio of NO3 in these products:
NO3 by itself weighs about 62 grams per mole.
Potassium Nitrate
(KNO3) weighs about 100 gram per mole, therefore NO3 is roughly 60% by weight of Nitrate.
Magnesium Nitrate
Ordinarily would have the formula Mg(NO3)2 but is typically sold in it's hydrated form Mg(NO3)2·6H2O (Magnesium Nitrate Hexahydrate 256 grams per mole) which lowers the percentage of Nitrate from 40% to about 24%. If someone sends you this product instead of KNO3 then you need to dose about 3X as much to get the same target Nitrate concentration that you would ordinarily get by dosing KNO3.
Calcium Nitrate
A similar story here. Ordinarily it has the formula Ca(NO3)2 but is typically sold in it's hydrated form Ca(NO3)2.4H2O (Calcium Nitrate Tetrahydrate 236 grams per mole) which lowers it's Nitrate content to about 53%.
Ammonium Nitrate
This is a completely different ballgame. Highly potent, use with care. This salt (NH4NO3) weighs a mere 80 grams per mole and is a Nitrogen superhero. Not only does it produce a whopping 74% Nitrate concentration, but the cation NH4 is also roughly composed of 78% Nitrogen. This is why most fertilizers, especially the terrestrial versions like Miracle Grow, derive at least some of their Nitrogen source via this salt.
Sodium Nitrate
While NaNO3 delivers a highly efficient 84% Nitrate concentration, Sodium, generally is very bad for plants and for most fish. So this salt should be avoided unless there are simply no other alternatives available at your location. It's efficiency at delivering NO3 however is good enough that depending on your lighting you might be able to use it effectively. It's also about 50% less soluble than Calcium Nitrate.
If you paid money for KNO3 then you need to ensure that it's what you got. I'll borrow the image from the EI tutorial. KNO3 is at the top of the image. You can see that it has a tendency to clump. Potassium Phosphate is shown in the middle of the image. You can see the difference in colour between the two salts. The Nitrate has a very slight yellow tinge in comparison. Also, most importantly, KNO3 has a funky, almost blue cheese odour to it, making it unmistakeable. Do not get fooled. If it does not have these characteristics then there is a strong probability that it is one of the other salts discussed above. This can easily explain why we have Nitrogen related difficulties.
EDIT: It should be noted that highly reputable sources of plant nutrients such as all of our sponsors, as well as garden centres such as Gardens Direct, have Quality Assurance measures in place to help ensure the integrity of their KNO3 and other dry powders. However, many anonymous internet trading sources do not. The mix ups may not even be intentional, as the vendor themselves may have been duped or they may not have systems in place to reduce the possibility of errors. Since almost all the various powders look very similar, i.e. all white powders, it is not surprising that mix ups can occur with identification, labelling , or shipping. Since we all know that Nitrate and Phosphate test kits are rubbish, then these are not reliable methods of determining which powder is which.
Top to bottom: KNO3, KH2PO4, Trace mix:
Cheers,
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