Continuing with the theme of nutrient disorders, diagnosis, & what to do about it; this week let’s talk about pH. What would you say if I told you that you could have a grow-room designed by a team of MIT engineers, Texas A&M botanists, & a fertilization program designed by top NASA scientists (what are they going to do now that they can’t put more men on the moon anyway?) So basically I am saying you have the very best of everything but if one little thing overlooked, even with all other necessities of plant growth met and surpassed your plants will shrivel and die in a few short weeks?
That’s right, it your pH. PH is short for potential of hydrogen. You may ask what kind of potential does hydrogen have? Does it want to grow up and become an astronaut?... it still can't go to the moon. All we really care about is that pH is a measure of acidity and alkalinity. It is measured on a 14 point scale 1 being the most acidic, 7 is neutral and 14 being the most alkali. This is a logarithmic base 10 scale so 9 is not just one point more than 8 on the scale, but it is 10 times more alkali, and likewise 10 is 100 times more alkali then 8.
A couple of tips about pH:
Always dilute your adjustment chemical (pH up or down) in a solution of water to about 1 part pH adjuster to 100 parts water. Use this to adjust you reservoir. Putting in a concentrated acid or base can cause localized chemical reactions and precipitates thereby binding your nutrients and disallowing them from being absorbed by your plants.
Most fertilizers are acidic and will lower the pH of a water nutrient solution. The main exception is a silica based additive (i.e. Rhino Skin by Advanced, Silica by Dutch Master, or Silica Blast by Botanicare) these are all alkali and will raise your pH.
Most fast growing annuals, i.e. tomatoes and peppers will thrive at a pH range of 5.5 – 6.5 in hydroponics, and a pH range of 5.8 – 7.0 in soil.
The ideal area to adjust your pH for hydroponics is 5.8, the ideal for soil is 6.3.
Different nutrients are absorbed at different pH values. It is best to adjust your solution to the lower end of the scale and allow the pH to fluctuate within the ideal range without adjustment so all nutrients are absorbed.
Chelated - a chemical compound that contains both a metal and an organic molecule in such a way that the metal is bound within the organic molecule and holds onto it like a "claw".
Why do you need to know this??????????
Because! Many of your micro-nutrients are metals and are often supplied in fertilizer in a Chelated form to allow them to dissolve into the water for easier plant uptake. Iron, Zinc and Manganese for example are often chelated. Although being chelated makes them more soluble pH extremes can affect their ability to dissolve. Iron for example can be chelated in two ways:
- Iron in the form of Fe-EDTA but this will become unavailable to your plant if the pH is raise above 6.0.
- Iron in the form of Fe-DTPA a more stable molecule (and expensive to produce) will remain soluble up to a pH of 7.0.
