Hydroponic Nutrient Solutions need to have the proper pH. It is important to balance the pH in your nutrient reservoir or tank.
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Q: What does pH have to do with mixing hydroponic nutrient solutions?
A: The plants absorb nutrients and oxygen through the roots. In order for the nutrients to be absorbed by the plant, there needs to be a "hole" or receptor for the specific nutrient with an opposite charge. Potassium is a Basic Metal with an M(1+) valence; Calcium and Magnesium are Basic Earth Metals with M(2+) valences.
Iron, Manganese, Zinc, and Copper are metals usually found in compounds with M- valences. Boron is a Metalloid which usually has a negetive valence.
Q: What are you talking about?
A: If the pH is high, Potassium, Magnesium, and Calcium are most easily absorbed; if the pH is low, Iron, Manganese, Zinc, and Copper are more easily absorbed. Different nutrients are absorbed best at different pH levels. When you mix up a hydroponic nutrient solution, keeping the pH level in the 6.0 to 6.5 range makes sure that all the nutrients can be absorbed. If the pH floats up too high or down too low some nutrients can be "locked out". pH problems don't show up as pH problems, they show up as nutrient deficiencies.
Q: How do I keep the pH at 6.0 to 6.5?.
A: The pH is always changing, so you should measure it at least once a day. The most common way is to use a liquid kit to measure. There is a small vial which you dip into the nutrient solution and fill up halfway. Then you add three drops of the tester solution, put the cap on the vial, and shake it a bit. The liquid in the vial changes color. Now, take the color of the vial and compare it to the color chart that comes in the kit. Try to use as close to natural light as you can because the colors given off by grow lights can throw off how the colors look.
Q: What if it's too high or too low?
A: There are bottles of pH UP and pH DOWN that you can use to adjust the solution. Depending on the size of the nutrient tank, it can take at least a half hour to three hours for the tank to fully circulate any adjustment. So after you add adjusting solution, you really have to wait before you test again to get an accurate reading.
Q: What if I test right away?
A: You will drive yourself nuts. The readings will never be close to each other twice in a row.
Q: Why can't I just use vinegar or battery acid to adjust the solution?
A: It's America, you can do anything you want.
Q: Will anything bad happen?
A: Probably nothing very bad, but you can do a whole lot better. Vinegar breaks down pretty fast and unevenly, so you will be adjusting a lot and your testing may be inconsistent. Battery acid is made for batteries, it is Sulphuric Acid which breaks down into compounds of Sulphur and Hydrogen ions. The strength is inconsistent and usually at a very strong concentration, but it breaks down at an even rate. If you don't have anything else--fine. But you can make your life a lot easier. It is the same for Hydro Chloric Acid except that you will get Chlorine compounds instead of Sulphur compounds. These left over compounds will be swimming around in your nutrient tank until you change out the solution.
Q: Why does the solution keep changing?
A: When the plants are growing, they pull nutrients out of the solution. More specifically, they pull the nutrient compounds apart into charged ions and absorb these ions into the plants. The stuff that stays in the nutrient solution eventually becomes the nutrient solution. These left over ions can change the pH. A positively charged ion is called a "cation", while a negetively charged ion is called an "anion".
Q: How do they change it?
A: Take Nitrogen, for example. Nitrogen is considered the biggest fuel for growth. Most good nutrient mixes use both a form of Ammonia and also Nitrate compounds. Ammonia floats around as either three or four Hydrogen atoms connected to one Nitrogen. (NH3 or NH4+) So when the Nitrogen is sucked off by the plant it leaves 3 or 4 Hydrogen ions floating around in the solution.
Conversely, when the Nitrogen is sucked off a Nitrate (NO3-, NOH, etc.), the result is OH- anions floating around the solution.
Q: So when the Nitrogen is used, it drives the pH in different directions?
A: You got it. When an H+ cation combines with an OH- anion, the result is H2O or water--stable and neutral. Good quality nutrient solutions use both ammonia forms of Nitrogen and nitrate forms of Nitrogen, like Calcium Nitrate for example. As the Nitrogen is absorbed by the plants, the leftovers balance each other out somewhat. This is why it's a good idea to use well made, quality nutrients sold by a reputable webstore.
