Hydroponics is a closed plant growing system that requires certain parameters in the system to be monitored and managed to provide the best growing environment for the plants. PPM is one metric that hydroponic growers must become familiar with to manage their systems correctly.
PPM means Parts Per Million, and it’s a unit of measurement that’s used to indicate the concentration of particles in a solution. In hydroponics, PPM measures the concentration of dissolved nutrients in the water. The correct level is crucial for proper growth and yield.
Hydroponics can sometimes seem intimidating when the technicalities of nutrient balance are mentioned, but it is important to understand these technical terms and what they mean for the success of your hydroponics system. PPM is one hydroponics metric you need to understand, but it is not too complicated.
If you don’t know much about how pH affects hydroponic gardening, I have an article called What Is pH In Hydroponics and Why It Matters, which covers this topic in detail.
What Does PPM Mean in Hydroponics?
Fortunately, there are not many complicated terms and measurements to understand in hydroponics, but the few that need mastering are important in the process.
PPM and pH are two of the most important aspects of growing hydroponically that every grower needs to understand and learn to manage.
The acronym PPM stands for a unit of measure called parts per million, and it’s a way of measuring the concentration of a solution. In hydroponics, ppm is used to measure the concentration of nutrients in the water.
PPM is so important in hydroponics because the plants are grown in water instead of soil and in a closed, controlled system. Fluctuations in the PPM levels can adversely affect plant growth and yield.
This characteristic of hydroponics means that the grower must replace natural processes and monitor and maintain the growing environment for the plants.
If the PPM is too low, the plants will not get enough nutrients, and they will decline in health and not produce the expected yield, or they could die. If the nutrient PPM is too high, the increased nutrient level can become toxic to the plants, which can cause them to die.
That’s why hydroponic growers need to keep an eye on the PPM levels in their hydroponic systems. You need to ensure that the levels are just right so your plants can thrive.
What Is the Difference Between EC, PPM, And TDS In Hydroponics?
If you read about hydroponics or interact with other hydroponic growers, you will hear some other terms mentioned alongside PPM. You may hear the terms EC and TDS mentioned in discussions about nutrient concentrations.
EC, PPM, and TDS all measure the concentration of dissolved compounds in a solution. Each of these measurement units can be described as follows.
- EC or Electrical Conductivity. Electrical Conductivity uses the electrical conductivity of dissolved solids in a solution to determine the concentration of the solution. The more dissolved solids, the easier the solution conducts electricity.
- PPM or Parts Per Million. PPM measures the concentration of minerals in a solution.
- TDS or Total Dissolved Solids. TDS measures the total density of the nutrients and minerals dissolved in a solution. The unit of measure for TDS is PPM, making these terms one and the same.
With each of these units of measure, the higher the number, the more nutrients are available for the plants, and the lower the number, the fewer nutrients are available for the plants.
The Most Common Measurement in Hydroponics
Of these measurement options, EC is the most commonly used in hydroponics. That’s because it’s the easiest to measure, and it’s a good indicator of the overall mineral content of a solution. PPM or TDS are less commonly used, but they can be helpful in troubleshooting nutrient problems.
There is some debate among hydroponic growers as to which measurement unit is better, but you can opt to use either standard for your hydroponics.
EC is more commonly used because the PPM meters on the market actually measure EC and use a calculation to report the PPM value. Depending on the calculation used, there can be a significant variance in the reported PPM on the meter.
However, it is useful to have both units available since the nutrient volumes from nutrient suppliers may be indicated in PPM or EC values. Most nutrient suppliers indicate both units in their instructions for mixing their hydroponic nutrients.
Hydroponic growers in the USA tend to favor PPM as the unit to measure nutrient levels, while the rest of the world generally uses EC as the preferred unit of measure.
Whichever unit you choose to use, monitoring the PPM and EC of your hydroponic system is essential to keeping your plants healthy and ensuring they get the nutrients they need to grow.
The YouTube video below gives a good overview of TDS, PPMs and EC.
How Do You Measure PPM In Hydroponics?
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There is only one main, cost-effective method to measure PPM: an EC/PPM meter. This device measures the electrical conductivity of the solution and uses that reading to calculate the PPM.
Typically, PPM meters come as EC and TDS or PPM combination meters, and some models include other important readings such as pH and water temperature.
There are various meters available, varying in quality and cost. We can recommend the GroLine pH/EC/TDS/Temperature Portable Meter and the AERO-GRO 5-in-1 TDS/pH Meter, both quality PPM/EC meters.
Conductivity meters aren’t always accurate, so it’s important to calibrate them regularly. The best method to calibrate a PPM meter is with a reference solution that has a known PPM level.
Knowing the PPM of your nutrient solution is important if you’re growing plants in hydroponics. It allows you to track how much food your plants get and ensure they’re getting the optimal amount.
What Should PPM Levels Be for Hydroponics?
When determining the ideal PPM level for your hydroponic system, there are a few factors to consider.
Different plants have different nutrient requirements, so growing plants with similar nutrient level requirements in the same hydroponic system is important.
For this reason, most hydroponic growers have more than one system to cater to plants with different nutrient concentration needs.
In general, most plants will do well with a solution with a ppm level between 1,200 and 2,500. However, starting on the lower end of this range is always best and gradually increasing the ppm level as needed. This will allow you to fine-tune the nutrient concentration based on the specific needs of your plants.
Another aspect of PPM levels to bear in mind is that plants need different nutrient concentrations at different stages of growth. It is important to know this information for each plant to give them the nutrients they need at each growth stage.
Hydroponics PPM Chart
Here is a Hydroponics PPM chart showing some common hydroponic crops and their PPM requirements at different growth stages as an example.
| Crop | Early Growth | Mid-Growth (Pre-Fruiting) | Adult Growth Or At Flowering And Fruiting |
| Strawberries | 800 – 900 PPM | 800 – 900 PPM | 400 – 500 PPM |
| Tomatoes | 300 – 500 PPM | 500 – 900 PPM | 1400 – 2500 |
| Cucumbers | 300 – 500 PPM | 800 – 1000 PPM | 1190 – 1750 PPM |
| Kale | 300 – 500 PPM | 560 – 840 PPM | 900 – 1500 PPM |
| Lettuce | 100 – 150 PPM | 200 – 500 PPM | 560 – 840 PPM |
If you notice that your hydroponic plants are not growing as well as they should be, the ppm level in your solution may be too low. On the other hand, if you see signs of nutrient burn ( leaf tips turning brown or yellow), this is an indication that the PPM level is too high.
How Do You Adjust PPM in Hydroponics?
The ideal ppm for a hydroponic system depends on the plants being grown. For example, leafy greens generally require a lower ppm than flowering plants.
Adjusting the PPM in water can be achieved by adding more or less of the concentrated nutrient solution to the water. If you have added too many nutrients, you can lower the PPM by adding more water to dilute the nutrient concentration.
It is important to keep track of the ppm levels in your system to make necessary adjustments as needed. Too high or too low of a PPM level can lead to plant growth and yield problems.
Conclusion
PPM is a unit of measure and stands for “parts per million” and describes the concentration of dissolved solids in a solution. In hydroponics, ppm is used to measure the concentration level of nutrients in the water. The higher the ppm, the more nutrients there are available for plants to absorb.
PPM is important because it determines how well plants will grow. If the ppm is too low, plants will not be able to get enough nutrients and will not grow well. If the ppm is too high, plants may get too many nutrients and could become “nutrient burned.”
The key objective of PPM levels is to find the right balance of nutrients for your plants so that they can thrive. By monitoring the PPM levels in your hydroponic system, you can ensure that your plants are getting the right mix of nutrients to promote strong and healthy growth.
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