Understanding N-P-K Ratio Of Hydroponic Nutrients

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An understanding of  N-P-K ratio is especially important when hydroponic gardening. Since we’re not just supplementing nutrients like in traditional dirt gardens, it’s even more critical that the correct nutrients are added in proper amounts for optimal growth. Fortunately, understanding N-P-K ratio is not too complicated.

What Nutrients Are Needed For Hydroponic Plant Growth?

Before explaining N-P-K, let’s talk about what a plant needs to grow. Plants require different nutrients in varying amounts throughout their life cycle. Nutrients that plants require more of are called “macronutrients” and those nutrients that are required in smaller amounts are “micronutrients”.

N-P-K stands for Nitrogen-Phosphorus-Potassium. These are 3 of the 6 macronutrients that plants require to live. The other 3, carbon, hydrogen and oxygen, are provided by water and the air. While hydroponic nutrients also contain the micronutrients, the focus is on the macronutrients.

The three number you see on the front of hydroponic nutrient is the N-P-K ratios and represent the percentage of each nutrient in the solution. For example, if the N-P-K ratio of a hydroponic nutrient is 7-9-5, then the nutrient contains 7% nitrogen, 9% phosphorus, and 5% potassium. The rest of the solution is made up of micronutrients.

What N-P-K Is Best For The Vegetative Stage?

During the vegetative stage, plants need higher amounts of nitrogen for foliage production. Nitrogen is the reason for the deep green color of your plants leaves when they’re healthy. Higher nitrogen levels speed up a plant’s growth rate.

This 7-9-5 ratio is a great all around vegetative nutrient for growing hydroponic vegetables.

What N-P-K  Is Best For The Flowering/ Fruiting Stage?

During the flowering stage, plants require a higher amount of phosphorus for flower and fruit production. At this point, the plant doesn’t need to keep producing leaf growth, so you decrease the nitrogen level while increasing the phosphorus level. (Phosphorus is also needed for healthy root production and is important in the early stages of root development also.)

This 3-12-6 ratio is good for vegetables that flower.

Hydroponic Supplements

During the different stages of the plant’s life, you can also give your plants a supplemental boost.  For example, plants in the fruiting stage use larger amounts of potassium and can often benefit from a potassium booster supplement. Potassium also assists with cell wall strength and overall health of the plant.  This is only one example of the many supplements available to customize the N-P-K ratios and give your plants a boost.

This 0-0-3 ratio potassium supplement boosts fruit production and overall plant strength.

There are many different types of hydroponic nutrients and supplements on the market with different N-P-K ratios. If you’re unsure what would work best for your garden I would suggest starting with a simple 1 part nutrient solution such as Dyna-Gro “Grow ” and “Bloom”, like pictured above. When you have a better understanding of N-P-K ratios and the specific nutrient needs of the plant type your growing, you can use a more customize-able nutrient solution such as General Hydroponics “Flora” series to tailor the nutrients to your garden.

11 Answers

  1. susantha padmakumara
    June 3, 2018 at 12:53 am

    I have started a hydroponic cultivation in styroform boxes. we have grown salad cucumber and tomato using albert solution.During the vegetative phase plants grew very well.But they produce very few flowers.Should we use a different nutrient solution for flowering stage? If so please tell me how to prepare that nutrient solution.

    1. NoSoilSolutions
      July 8, 2018 at 3:19 pm

      Yes you will need a different nutrient solution for the flowering and fruiting stages. Look for a nutrient solution with more phosphorus. General hydroponics has a good three part solution or Dyna Gro has a one part solution you don’t have to mix.

  2. Susan
    December 8, 2019 at 8:06 pm

    I Am researching different seeds to grow fodder for my horses – Barley, wheat, and oat. The biggest issue I am looking at is the ratio of calcium to phosphorus is off on the seeds. What I need to achieve is Calcium at .43-.58% and phosphorus at .20-.26%. Wheat has calcium at 11% and phosphorus at 54% for example. When I am adding NPK is there calcium supplement that can be added to offset the imbalance?

    1. NoSoilSolutions
      December 8, 2019 at 11:09 pm

      Hey Susan!
      I’m not super familiar with fodder, though I do grow barley sprouts for my chickens and turkeys in the winter. Are you asking how to change the nutrients of the fodder itself? I don’t use nutrients to grow my fodder only water.

    1. NoSoilSolutions
      December 11, 2019 at 7:49 pm

      I’m not too sure on the correct answer so I don’t want to tell you wrong. My thought would be that the extra nutrients your providing the plant is not going to increase the nutrient level for the animals like your wanting. I would think it would be better to provide the horse with a nutrient supplement.

    2. Vaidyanthan
      January 28, 2023 at 6:47 pm

      We are using 20 20 20 N P K for green leafy vegetables in hydroponic system.
      But the water becomes acidic in two days.
      Pl suggest what to do

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