A Perfect PH Primer: The Basics… And The Acids Of Plants And PH
Understanding pH and knowing how it works in relation to your plants is a valuable skill when it comes to gardening. Properly managing your pH can go a long way into perfecting your yields and getting the most out of your fertilizers and hard work. At Token Grow, that is what we are all about, your success. Although pH is pretty simple in soil culture, it can be a bit more crucial in water culture systems like hydroponics, aquaponics, or aeroponics. Don’t worry though, we’ve got your back and will go over the basics of everything in this primer.
What Is PH?
The pH level is a measure of how basic or acidic a substance is. It is essentially two different scales stuck together that meet in the middle at 7, which is neutral. A pH between 7 and 14 is basic and measure the amount of OH- ions in solution. A pH between 7 and 0 is acidic and measure the amount of H+ ions in solution.
This next part is a bit technical but something to keep in mind. The pH scale is logorithmic and each level is 10 times stronger than the previous. So a pH of 10 is 10 times more basic than a pH of 9 and 100 times more basic than a pH of 8. This means that a small change in pH can actually equate to a large difference.
How Does PH Affect My Plants?
The proper pH is essential for plants to be able to grow and absorb nutrients. If the pH of the substrate the plant is in is too extreme, nutrients and minerals will be in the wrong form for the plant to be able to absorb it. In other words, if your pH is off, your plants will get deficiencies even if you are adding the right nutrients and minerals. Plants do not have the ability to get up in move when things aren’t perfect for them so you have to help make sure that the pH they are growing in is ideal. Most plants prefer a pH that is neutral or slightly acidic but there are specific ranges of pH that each plant functions best in. Be sure to check for this range for your specific plant in a book or online if you are suspecting a pH issue.
Grow Media Also Affects PH
Your grow media, or substrate, also has a PH. This affects the availability of both micro and macro nutrients. A pH that is too acidic can lead to metal toxicities such as Manganese and Aluminum toxicity. Highly acid soils also allow metals to bind phosphorous and cause phosphorous deficiencies. Conversely, in alkaline soils, the uptake of most macronutrients is affected. Ph that is too high can also lead to magnesium deficiencies by binding it all.
Testing The PH
It's easy! Just as easy as dipping a piece of paper into some muddy water. In all seriousness, there a couple different ways to measure the pH of your soils or water. The cheapest, and easiest by far, is to get pH strips, you may have seen these used for home pool maintenance. They are available inexpensively online or sold in most garden centers as a part of soil test kits. Another option, and useful if you are fertilizing a lot of plants or if you are growing in water based culture, is an electronic pH meter. These are a bit trickier to use as they have to be calibrated but they come with easy to use instructions and are very precise. It can make all the difference to make sure your irrigation water in a greenhouse set up is the right pH.
PH And Soils
Different types of soils naturally have different pH values due to the different components that make them up. Heavy soils with naturally high mineral contents, or high clay content, have lots of what are known as base cations which make them more basic. Things such as Mg2+, Ca2+, K+ and Na+ all contribute to making the soil more alkaline.
The good news is, most soils have a high component of organic matter known as humus, this is the black part of black soils. This stuff is full of all sorts of organic acids including humic acid and tannic acid. This helps make the overall mixture a bit acidic which is perfect in most cases. Many plants are also capable of altering the pH of soils slightly around their roots to tailor it to what they need. So as long as your soil is in the neutral range, leaning towards acidic, most plants will survive. Keep in mind that every level of the pH scale is 10 times larger than the previous level or 10 times smaller than the next level. Even being a bit out of the acceptable range can affect the plants health greatly.
So, if your soil is too alkaline, try adding some nice rich compost, manure, or black dirt to add some structure too it and help negate the high proportion of minerals. This has a buffering effect but if you need to really lower the soil pH, there are some stronger options. Elemental sulfur or sulfate compounds can be bought and used to buffer strongly alkaline soils, the form sulfuric acid in the soil mix, helping to neutralize it. Nitrogen fertilizers also have the effect of decreasing the pH, usually just enough in a neutral soil to make it optimal.
On the other hand, if your soil is too acidic, it probably just has too high a ratio of organic matter, this can be diluted with something inorganic like clay, rock dust, crushed limestone or sand. Sand also has the added benefit of preventing compaction which is common in highly organic soils. Horticultural lime and wood ash will also quickly help you raise the pH of your soil.
PH And HydroponicsFor hydroponics, aquaponics and aeroponics, there is no soil. This means that you loose the buffering capacity of the organic component of the soil. This means you have to add you own nutrients to these systems and makes these systems more sensitive to pH changes caused by the addition of new water or fertilizers. In aquaponics systems, you have to also understand what a healthy range of pH for your fish is and find the happy medium for your plants and fish. This is where understanding and managing pH becomes key.
It is important to understand how the addition of any mineral, fertilizer or nutrient solution can affect your system. This can be done by understanding and knowing the pH of the solution you are adding and also understanding how dilution and pH works. Simply put, if you add something acidic, it will lower the pH and if you add something alkaline, it will raise it.
Know The PH of Your Source Water
First, know the pH of your source water. It is easiest if this is as close to neutral as possible but you can work with pretty much any starting pH. Then add your nutrients and see how it has changed, most fertilizers will lower the pH. Next adjust it using either an acid or base. Phosphoric acid is often used to lower pH and potassium hydroxide is used to lower it. Both are readily available at hydroponics shops and come with dosage instructions. As your plants use up the nitrogen compounds in the fertilizer, the pH will rise so be sure to check it often until you have a sense of how fast this happens. Also note that as plants get larger they will use fertilizer faster and the pH will rise faster.
When All Else fails… Pick The Perfect Plant
In some cases, such as landscape gardening in heavily alkaline soils or in areas with lots of limestone, it may not be possible, or feasible, to change your soil chemistry en masse. For example, if you are planting 50 landscape trees, it is a better idea to pick something that fits your soil chemistry rather than having to tweak the soil chemistry every year in order to keep your trees healthy. Nature has come up with solutions for a lot of different soils.