I have just read the post on the RO fertilizer.
To me:
- The powder fertilizers are NOT stable
- The liquid fertilizers are NOT stable, and I would strongly suggest against doing a liquid concentrate of any given fertilizer.
Let just have a simple look at some basic chemistry and how to understand the problem:
* A fertilizer is composed of several salts, blended or dissolved together. You must read the composition of the fertilizer, both the percentages and the 'derived/made from ammonium nitrate, potassium dihydrogenphosphate, etc...', that is included in the fertilizer, or downloadable on the internet from most if not all the serious fertilizer manufacturers.
* Calculate the weight of each of those basic salts. It can be done with Excel as an example. If the fertilizer says as an example
"Fe from Fe chelated EDTA", we know that the Fe EDTA contains 0.152% of Fe, 100mg of Fe chelated by EDTA contains therefore 15.2mg of iron.
It is just boring to make the calculations, but for those ones who want to do in detail...
* Download
http://www.lwr.kth.se/English/OurSoftware/vminteq/
Visual Minteq is a freeware which can be use for a wide range of purposes. For our purposes, we enter all the mineral salts from the fertilizers, and can modelize the chemical reactions that will happen when all those salts are put together, 'nearly dry' or in stock concentrate solutions. Visual Minteq is highly reliable...
We found easily that for all except the most basic NPK only fertilizers, some precipitate will occur, eventually locking completely one nutrient, micro or macronutrient. Especially around the calcium/magnesium/phosphate/sulfate story for the macroelements, and the Iron/Copper/Calcium/EDTA/EDDHA for the microelements.
Having a 'dry' fertilizer is impossible, as first we have hydratation molecules of some of the salts. The calcium nitrate is in the tetrahydrate form for the fertilizer production. The anhydrous stage can be sometimes found, but it will hydrate easily, so it is not that useful...
Second, the air humidity will anyway bring water molecules in the powder. There is nothing to do against that.
With MinteQ, you can modelize how the powder will perform, by increasing the water content to a very small quantity. This explains why for many fertilizers, a precipitate will occur when they are dissolved. Anyway...
For the stock solutions, like 50g/L or that kind of stuff, the problem is far more dangerous. The precipitate occurs at the molecular, or microaggregate levels, so it cannot be seen by the naked eye. We make what is called a colloidal solution this way, when the precipitation will occur, the resulting useless for the plant molecules will disperse more or less evenly in the solution. This reaction can take some seconds or some hours. Anyway, the proper way to make a quick to use stock solution is to put the powder in the water, not the water on top of the powder, as some compounds can form extremely quickly, like calcium sulfate or calcium phosphate...
One way to delay the problem is to make the solution very acidic, but it is not practical, as after we have to correct the pH of the water/fertilizer solution. And the EDTA/EDDHA chelated compounds can make funny things at very low pH required to keep the calcium, phosphate, sulfate, and magnesium safely as ions in the solution... There is no 'best solution' actually...
This is again for people who really want to fine tune everything, because at the practical level, most fertilizer will do well by themselves, even with the lost micronutrients or a part of the macros that are precipitated.
To me:
- The powder fertilizers are NOT stable
- The liquid fertilizers are NOT stable, and I would strongly suggest against doing a liquid concentrate of any given fertilizer.
Let just have a simple look at some basic chemistry and how to understand the problem:
* A fertilizer is composed of several salts, blended or dissolved together. You must read the composition of the fertilizer, both the percentages and the 'derived/made from ammonium nitrate, potassium dihydrogenphosphate, etc...', that is included in the fertilizer, or downloadable on the internet from most if not all the serious fertilizer manufacturers.
* Calculate the weight of each of those basic salts. It can be done with Excel as an example. If the fertilizer says as an example
"Fe from Fe chelated EDTA", we know that the Fe EDTA contains 0.152% of Fe, 100mg of Fe chelated by EDTA contains therefore 15.2mg of iron.
It is just boring to make the calculations, but for those ones who want to do in detail...
* Download
http://www.lwr.kth.se/English/OurSoftware/vminteq/
Visual Minteq is a freeware which can be use for a wide range of purposes. For our purposes, we enter all the mineral salts from the fertilizers, and can modelize the chemical reactions that will happen when all those salts are put together, 'nearly dry' or in stock concentrate solutions. Visual Minteq is highly reliable...
We found easily that for all except the most basic NPK only fertilizers, some precipitate will occur, eventually locking completely one nutrient, micro or macronutrient. Especially around the calcium/magnesium/phosphate/sulfate story for the macroelements, and the Iron/Copper/Calcium/EDTA/EDDHA for the microelements.
Having a 'dry' fertilizer is impossible, as first we have hydratation molecules of some of the salts. The calcium nitrate is in the tetrahydrate form for the fertilizer production. The anhydrous stage can be sometimes found, but it will hydrate easily, so it is not that useful...
Second, the air humidity will anyway bring water molecules in the powder. There is nothing to do against that.
With MinteQ, you can modelize how the powder will perform, by increasing the water content to a very small quantity. This explains why for many fertilizers, a precipitate will occur when they are dissolved. Anyway...
For the stock solutions, like 50g/L or that kind of stuff, the problem is far more dangerous. The precipitate occurs at the molecular, or microaggregate levels, so it cannot be seen by the naked eye. We make what is called a colloidal solution this way, when the precipitation will occur, the resulting useless for the plant molecules will disperse more or less evenly in the solution. This reaction can take some seconds or some hours. Anyway, the proper way to make a quick to use stock solution is to put the powder in the water, not the water on top of the powder, as some compounds can form extremely quickly, like calcium sulfate or calcium phosphate...
One way to delay the problem is to make the solution very acidic, but it is not practical, as after we have to correct the pH of the water/fertilizer solution. And the EDTA/EDDHA chelated compounds can make funny things at very low pH required to keep the calcium, phosphate, sulfate, and magnesium safely as ions in the solution... There is no 'best solution' actually...
This is again for people who really want to fine tune everything, because at the practical level, most fertilizer will do well by themselves, even with the lost micronutrients or a part of the macros that are precipitated.