pH and PPM: Knowing What Your Plants Are Eating and How Much They Can Handle

One big question growers ask is why the heck their plants are suffering even though they used all the right nutrients, feeding cycles, lighting cycles, and adjusted temperatures and conditions to their absolute best.

That’s because their pH and PPM levels are off, making it difficult for your plants to eat. pH refers to potential of Hydrogen ions in your water, which will determine if your water is too acidic or has too much alkaline in it. PPM (parts per million) refers to the concentration of minerals and soluble matter in your watering solution.

Correct pH and PPM levels are the backbone of any grow, and will be the difference between a healthy grow and a huge waste of time and money.

pH Levels

Simply put: the right pH level will create an environment where your plants can absorb nutrients quickly and easily, leading to a better harvest.
pH levels is important to understand because the right level will determine the quality of helpful bacteria available in your solution that help break down elements in your solution, and help the metabolic rate of your plants.

When pH levels are too low (pH level of around 5 of lower), heavy metals like iron and aluminum change and can become toxic to your plants. If the pH level is too high (pH level of around 6.5 or higher) elements like calcium and phosphorus can’t be broken down completely, which will hinder the growth of your plants.

phppm2Remember: too low= toxic to your plants, too high= growth decrease. That’s why you want to have the perfect level of acidity in your water, which will be around 5.5-5.8

Typical pH Levels (Hydroponic applications)

  • 3.5 and below: Root Damage
  • 4.0-4.5: Poor Nutrient Uptake
  • 5.0-5.4: Good pH Level
  • 5-5.8: Perfect pH Level
  • 6.0-7.0: Acceptable pH Balance
  • 5.0-8.0: Poor Nutrient Uptake
  • 8.5 and Above: Root Damage

PPM Levels

PPM: Parts Per Million. This refers to concentration of the particulates in your feeding solution. Those particulates can be anything from minerals found in tap water to natural elements found in your nutrients, and your job is to make sure that the PPM levels are on point so you’re not under- or over-feeding your plants.
While it’s an easy concept to understand on the surface, it’s a little more complicated when you have to adjust elements. Now, pH plays a huge factor in PPM levels because even though you may have the correct PPM reading, some of the particles- and the concentration of those particles- can be harmful for your plants.

phppm3For example, let’s say your plants need to be at a PPM level of 700. You mix your solution and you get a PPM reading of 700 but your pH is around 4.5. That means that the majority of the available food for your plants is likely to have lots of heavy metals in it, which will quickly toxify the plant. You’ll need to adjust the pH level of your solution to make sure you’re not toxifying your plants.

“But won’t that throw my PPM levels off because you’re adding particles to your feeding solution?” It can, and that’s what’s so tricky about PPM and pH levels. When you adjust one, you usually have to adjust the other, which can be simple or a huge pain depending on the water and nutrients you’re feeding your plants.

Common PPM Readings

  • Seedlings: 100-250
  • First Half of Vegging Cycle: 300-400
  • Second Half of Vegging: 450-700
  • First Half of Flowering: 750-950
  • Second Half of Flowering: 1000-1600

Adjusting pH Levels
phppm5-the-weed-blogWhen it comes to feeding plants there’s two ways of looking at it: homemade or store bought. Same goes with balancing your pH: you can either purchase a pH buffer from a store or you can use ingredients you can find around your home or in the grocery store- but both come with their advantages and disadvantages.

If pH levels are low you can use a little citric acid or even white vinegar to help bring your water’s pH down. When you need to raise your pH levels you can use a little bit of baking soda in your solution and bring those readings back up. The issue with using these solutions is that they don’t work for very long. You’ll find yourself having to add a little lemon juice every other day, then having to use a little baking soda to even things out. Moreover, we’ve also heard of growers using these ingredients and seeing severe spikes in pH, which if not handled properly and quickly and bring your grow to a halt.

Most hydroponic companies out there will have pH buffers, usually called pH Up & pH Down. The great thing about these solutions is that not only do they have a variety of ingredients to help adjust your water solution, but they’re designed as buffers that will keep your water maintained for longer than it would be without them. But like we’ve always mentioned, easier usually means more expensive. These solutions usually won’t cost you an arm and a leg, but they’re definitely something you can’t simply make at home and will cost some money.

Adjusting PPM Levels
Before you start adjusting your PPM levels, you’ll first want to make sure your tap water is ready to feed your plants. Now remember that your plants’ water will need to be at different PPM’s during its lifetime, so you’ll want to give your nutrients a good enough environment to work in. That means you’ll want to adjust the PPM of your base water before you start feeding it to your plants.

To rid your water of too many particles, you can use things like a carbon filter or a reverse osmosis machine to clean your water. However, many growers agree that most tap water has helpful minerals (like calcium and magnesium) that actually help plants. During and after the vegging stage, your plants will want more out of their feedings so filtering isn’t too necessary. That’s why we recommend only using filters at the beginning of the plants life when low PPM readings are needed, or for adjusting PPM.

Filtered, pH’ed water is great when things get a little too much in your reservoirs. When PPM’s are high, just add a bit of fresh water with a good pH level and watch them drop.

When readings are low it’s usually time to feed your plants. When you add nutrients to your feeding solution your PPM’s will go back up, and when your PPM’s and pH’s are in balance your plants are going to be happy and healthy. Just remember that these readings need constant adjustment, so if you haven’t been keeping a close eye on your plant’s PPM and pH levels there’s not better time to start than now.

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