How to Adjust pH

The pH is adjusted by using an acid to lower it or a basei to raise it. There are many products sold by HTGsupply.com,  that you can use to adjust your pH.  I have used General Hydroponics' pH down and pH up. Many acids and  bases are extremely corrosive and dangerous, so extreme care should be used if you are not using a product labeled for hydroponic use.
I have written about adjusting the pH in soil medium on another post.
Always follow the directions of any product you use, but you should start out adding one milliliter per gallon. Wait 15 - 30 minutes, and test your water again. Frequently you will only need 1 to 2 ml of pH Up/Down per gallon of water. Keep in mind you may need additional pH Up/Down if you have hard water. The General Hydroponics Flora Series is pH buffered to facilitate keeping the pH in a favorable range.
Something I will say may surprise you, pH is not as critical as most growers believe. The main point is to avoid extremes in pH. Plants can grow on soils with a wide range of pH. However, the pH does not jump to extremes in a soil. So, the real secret is to make sure you keep your plants in a moderate pH at all times. For most plant species there is an optimum pH in the region of pH 5 to pH 6.5

The most popular componets of pH adjusters are phosphoric acid (to lower pH) and potassium hydroxide (to raise pH). Both of these chemicals are relatively safe, although they can cause chemical burns and should never come in contact with your eyes or mucus membranes. I would recommend using pH adjusters that are diluted to a level that is reasonably safe and easy to use. Concentrated adjusters can cause large pH changes and can make adjusting the pH very frustrating.

It is worth saying again, always add your nutrients to the water a few minutes before checking and adjusting the pH of your solution. The fertilizer will usually lower the pH of the water due to its chemical makeup. After adding your nutrient and mixing the solution, check the pH using whatever method you chose. If the pH needs to be adjusted, add the appropriate adjuster. Use small amounts of pH adjuster until you get familiar with the process. Recheck the pH and repeat the above steps until the pH level is where you want it to be. Once you have done this a few times, you'll know how much to give your plants the first try.

Most of the time, the pH of the nutrient solution will have a tendency to go up as the plants use the nutrients. As a result the pH needs to be checked periodically and adjusted if necessary. To start out, I suggest that you check pH minimally on a daily basis. Each system will change pH at a different rate depending on a variety of factors. The type of growing medium used, the light cycle, the kind of plants and even the age of the plants all effect the pH variations.

Good Growing
Dr. E.R. Myers


Causes of pH Change and How Nitrogen Affects pH

This is the 200th post on this blog.  Thanks for all the questions and comments!
Most varieties of vegetables grow at their best in a nutrient solution having a pH between 5.5 and 7.5 and a temperature between 20 and 22C. (68F-72F). Good growers need to find the best pH for their plants but should always start in this range.  See my post on how to check the pH of soil and soiless mixes

Why does the pH change?  A simple explanation as to why the pH changes is that plants will take up nutrients from the water and when these nutrients are taken from the reservoir this changes the pH.

The light cycle also affects pH, you should check the pH at the same time of the light cycle when you check it. If you think you have pH problems, you should check it several times a day throughout the light cycle. If you have an accurate pH meter and keep notes you can actually plot and see how the pH changes for your plants throughout the day.

When you provide light to plants they can do photosynthesis which is a metabolic pathway that produces various ions. During the dark cycle, photosynthesis stops but plants still do cellular respiration and if you are using beneficials  they will be respiring too. All this respiration and don’t forget the decomposition of organic matter in the solution leads to pH changes. If you are having pH prolems cleaning out the reservoir can sometimes help, if you have leaves or plant pieces in the reservoir their decomposition can change the pH and can lead to other problems with fungus.

In low light plants take up more potassium and phosphorous from the nutrient solution so the acidity increases (pH drops). In strong intense light plants take up more nitrogen from the nutrient solution how this affects pH depends on the type of nitrogen you are giving your plants.

Nitrogen is the inorganic nutrient required in the largest quantity by plants. Most plants are able to absorb either nitrate (NO3-) or ammonium (NH4+) or both. NH4+ as the only source of nitrogen or in excess is harmful to the growth of many plant species. Some plants yield better when supplied with a mixture of NH4+ (ammonium) and NO3- (nitrate) compared to NO3- alone. Good Growers will experiment to see what ratio is best for their plants. Good growers also know a combination of NH4+ and NO3- can be used to buffer against changes in pH.

Plants grown in nutrient solution containing only NO3- as the sole nitrogen source tend to increase solution pH - hence the need to add acid.  But when approximately 10%-20% of the total nitrogen is supplied as NH4+, the nutrient solution pH is stabilized at pH 5.5. You may end up with less NH4+ than you add if you use beneficials.  It has been shown recently that micro-organisms  growing on plant root surfaces can convert the NH4+ to NO3-.
Good Growing,
Dr. E.R. Myers


E-mail - pH crashes in hydropoinc system

Hey Doc,
   I bought my hydroponics system from HTG but the pH in my system crashes to 4.0 every week or so, how can I stop this or stabalize it?

Thanks for your question.  The easiest way is to add pH up. Sometimes pH crashes because of the presence of a large amount of microbial activity in the nutrient solution. If you flush the system each week and generally keep up maintenance of the system you should avoid this scenario. If you are not adding beneficial microbes, you might want to think about adding them. If you check out the HTGSupply.com website and beneficials that are specifically for hydroponics this might help as well.

I will be writing about specific pH adjustment in the next blog, thanks for the question!

Good Growing,
Dr. E.R. Myers


Checking the pH with Hydropnics

When you are growing hydroponically checking and adjusting pH is a simple but very important thing to do. There are several ways to check the pH of the nutrient solution in your hydroponic system.

HTGSupply.com sells all of these products, look on their webpage under Monitering and Test Equipment.  To start, you can use paper test strips which are the most inexpensive way to check the pH of the nutrient solution. These paper strips have pH sensitive dye which changes color when dipped into the hydropinics nutrient solution. You then have to match the color of the strip to a chart to see what the pH is. These test strips are inexpensive, but they can be hard to read, because the colors differences are subtle. If you are going to be trying different nutrients etc. or are seriously into growing hydroponically, you might want to get a digital pH meter.

A step up from the paper test strips are liquid pH test kits. These are more a popular method to check pH for the hobby gardener. These liquid test kits work by adding a few drops of a pH sensitive dye to a small amount of the nutrient solution and then comparing the color of the resulting liquid with a color chart. While slightly more expensive than the paper test strips, they are easier to read and are more accurate and reliable.

The Most high-tech way to check pH is to use the digital meters. These meters come in a huge array of sizes and prices. Unless you are also going to use your pH meter for chemistry, YOU DO NOT REALLY NEED A METER THAT GOES FROM 1-14, you only need a meter that checks pH between 4-9 since that is the range plants need. With most  digital pH meters you simply dip the electrode into the nutrient solution for a few moments and the pH value is displayed on an LCD screen.
The problem with hydroponics is that while it gives the grower more control of nutrients and pH it is also easier to mess up. The same goes for a digital pH meter.  Digital pH meters are very accurate (when properly calibrated) and fast but they need to be cared for properly however, or they will quit working. The glass bulb electrode must be kept clean and some are required to be wet at all times. What these pH meters are doing is checking the voltage in the water, so corrosion or misuse of equipment will break the device. The pH meters usually need to be calibrated frequently, (Just follow manufactuers instructions) as the meters can drift (give the wrong pH value) and to insure accuracy you must check calibration often. With some digital meters, the tip needs to be stored in an electrode storage solution or in a buffer solution and should never be allowed to dry out
The pH meters are slightly temperature sensitive. Many of the more expensive pH meters on the market have Automatic Temperature Compensation (ATC), which corrects the reading with respect to temperature. On meters without ATC the pH should be checked at the same time of day each time in order to minimize any temperature related fluctuations. Again, you don’t need ATC if you will always check at the same temperature, don’t buy all the bells and whistles if you don’t need them.
Due to the fact that pH meters have a reputation of breaking down without warning it is a good idea to keep an emergency backup for checking pH (paper test strips or a liquid pH test kit), just in case.
Good Growing,
Dr. E.R. Myers


Hydroponics and pH Basics

Happy New Year! and Happy Birthday P.J.!

The pH is very important in hydroponic gardening.   I will talk about some specifics of measuing pH in a later post.  The pH is measured on a scale of 1-14 with 7.0 being neutral. Acids are lower than 7 and bases (alkalinity) are above 7.
In order to understand how nutrients affect pH you should know the term pH is a measure of the hydrogen-hydroxyl ion content of a solution. These are the two components if you break apart water H2O (H+ and OH-). Pure water has an equal balance of hydrogen (H+) and hydroxyl (OH-) ions and is therefore pH neutral (pH 7.0). {Substances (molecules or atoms) with a charge are either positive or negative and are termed ions}. Since distilled water is pure water it has a pH of 7.0.  This is too high a pH for mos plants so I don't recomend using it without adding nutrients. When you add nutrients to water it can have a pH either higher or lower than 7.  If the solution has more hydrogen (positive) ions than hydroxyl (negative) ions then it is an acid (less than 7.0 on the pH scale). Conversely if the solution has more hydroxyl ions than hydrogen it is alkaline (or a base), with a pH greater than 7.0
When the pH is not at the proper level the plant will lose its ability to absorb some of the essential elements required for good growth. This depends on the plant and the nutrient. Some plants need a high amount of iron, and since iron becomes increasingly unavailable to plants as the pH approaches 8.0, these iron needing plants do poorly in basic mediums. For all plants there is a particular pH level that will produce optimum results, good growers experiment until they find their best or optimal pH for their plant(s). This pH level will vary from plant to plant, but in general most plants prefer a slightly acid growing environment (between 5.5-6.5), although most plants can still survive in an environment with a pH of between 5.0 and 7.5.
When pH rises above 6.5 some of the nutrients and micro-nutrients begin to precipitate out of solution and can stick to the walls of the reservoir and growing chambers. If you notice residue or salts in your reservoir when you change the water, you might want to adjust your pH down a bit. To use iron as an example again… Iron will be about half precipitated at the pH level of 7.3 and at about 8.0 there is virtually no iron left in solution at all. In order for your plants to use the nutrients they must be dissolved in the solution. Once the nutrients have precipitated out of solution your plants can no longer absorb them and will suffer deficiency and death if the pH is left uncorrected.
Not all nutrients will affect the pH the same! In other words you can manipulate the pH with the nutrients you add. Good growers will know nitrogen (an element required in large quantities for healthy plant growth) may be supplied in two forms (ammonium - NH4+ or nitrate - NO3-). These two forms of nitrogen when added to the nutrient solution  will result in different changes can result in large pH changes.
More on pH to come...
Good Growing,
Dr. E.R. Myers