Managing pH in Stonewool Grow Media

Posted on December 14, 2020 by Red Rock Block

A Guide to Balancing pH in a Hydroponic System: Learning the ‘Basic” Nature of pH

Over recent years the greenhouse industry has shifted from the traditional in pot growing methods to one that is more precise and efficient. Precision Agriculture has taken the production industries by storm with the focus of high quality crops and products with less inputs and strains on the environment. Once precise application used in the commercial food and flower production industry is hydroponics. In hydroponics, crops are grown in a soilless media or substrate with either a flooded system or one with water ran through on a timed basis. There is no soil and has better ease of controlling aspects like pH, nutrients, and other growing requirements.

When setting up and running a hydroponics system, there are several choices for substrate to be used. Although this is a soilless system, the plants still need something to grab onto. There are other system types such as aeroponics that have plant roots hanging freely without a substrate. However, in hydroponics the most common method is through a basket placed in the system with a substrate such as coco coir, clay pebbles, or stonewool. Even though this method is not like the traditional spilled approach, the grower still needs to be aware of the requirements and needs of the plants in pH, nutrients, and EC. The monitoring of these is different in hydroponics in comparison to traditional horticulture. Depending on the substrate, the control of the pH and EC will differ in the monitoring and overall approach to control.

pH Explained

Before being able to adequately control and monitor pH, it is important to fully understand what pH is. pH is the unit of measurement for nutrient solution acidity or alkalinity. It is called pH due to the description of the Hydrogen + ions in the solution, substrate, or drain water. The higher the number of H+ ions the more acidic and the lesser the H+ ions the more basic. Control of pH is the direct control over the number of ions in the solution through additives and other solutions.

Stonewool and Acquiring Target pH

When monitoring and controlling pH and EC, container substrates such as peat, coir, vermiculite, and soil products have a relatively moderate buffering capacity. Having a moderate buffering capacity translates to a media needing to have a large change of effect in regards to the pH levels. These are done through fertilizer or acid injection into the soil or media. In most cases, to fully change the pH of these media, it takes roughly a week before changes are seen. In comparison to hydroponics, the pH can be quickly changed because of the lower buffering capacity. pH can be changed in a  day or two in comparison to the week for other media and growing styles.

With a lowered buffering capacity, it is crucial to monitor the system daily to ensure changes to pH do not occur that can affect a plant negatively. Stonewool is neutral once set up into a system and flushed with water and solution. Depending on the type of manufacture, some stonewool may be on the acidic side from the rock material it is made of. By soaking the material, the pH can be neutralized. With the neutral nature of the material, the pH is solely dependent on the nutrient and fertilizer solution running through the system. By monitoring the system either daily by hand or through an automated system, pH and EC can be effectively monitored and changed when needed.  When using a reservoir system in place of a direct line system, a grower should allow for the system to fully circulate and mix with the water and solution in the reservoir before making additional adjustments to the pH and solution.

How to Control pH in a Hydroponic System Using Stonewool

Controlling pH in a hydroponic system allows for certain elements and nutrients to be readily available for the plant to take in. Issues with the pH will cause the plant to lack nutrients and overall effect on the growth and quality of the plants. Typically the elements iron, manganese, and zinc become less available when the pH raises to a more neutral or slightly basic level of 6.5-7.5. At a higher pH, phosphorus becomes unavailable. With these elements, no matter how much is placed into the solution, it will be unavailable and plants will show deficiencies. In order to prevent such events, an operator needs to accurately and effectively monitor the pH in the stonewool material.

stonewool-starter-block-grow-blocksMonitoring the pH in the stonewool is essential in the nutritional monitoring of the system. This can be done either manually or through automated equipment. Sampling the material from multiple places will give a good representation of the pH in the growing system. In order to take accurate measurements, pH should be measured through calibrated equipment and tools using standard solutions. Checking the condition of these tools and equipment such as battery life, accuracy, and looking for damage is key. The pH readers should always be stored in the correct deionized water solution when not in use to prevent corrosion or inaccurate readings. The pH meter should be stored in a cool and dry place to prevent compromising the device. Whether a grower goes with a manual or automated system for the control and monitoring of pH really depends on the growers preferences, budget, and overall plant needs.

For advice and assistance on the selection of pH control and monitoring systems and tools, reach out to one of RedRock Block’s expert staff who are backed by decades of combined experience in the field. With free services in planning, and additional other AG grow services in installation, maintenance, and repairs RedRock Block is the go to source for all things commercial and industrial horticulture no matter the type of operation or the crop being grown.

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