Adding Nutrients and Adjusting pH in Your Hydroponic Garden

Adding Nutrients and Adjusting pH in Your Hydroponic Garden

Overview:

When growing with hydroponics, ensuring you have the right nutrient mix is essential to both the growth and taste of your plants.

Adding nutrients and pH balancers to your hydroponic solution should be a multi-step process.  And before you begin, you should always make sure that you have a hydroponic TDS (Total Dissolved Liquids) or EC (Electrical Conductivity) sensor and a pH sensor available.  These sensors are relatively inexpensive.  They’re available at your local hydroponics shop, Amazon.com, and soon IGWorks.com.  If you’ve purchased an iHarvest, you will be receiving a TDS and pH sensor with your purchase.

Note that TDS sensors and EC sensors are actually the same thing, but most sensors convert from an EC value to a TDS value.  It will be obvious to you what value is being provided, as EC values generally range from 0 – 5, and EC sensors have values much higher (typically from 100-2,500). Whether you're using a sensor that produces EC or TDS results, you can use the chart at the bottom to get your nutrient and pH mix right for the fruits and vegetables you want to grow.

TDS and EC Sensors:

Let’s briefly discuss what these sensors are and how they work.  As stated above, both EC sensors and TDS sensors are the same thing, but they produce different values.  Both sensors use electrical conductivity to measure the amount of nutrients in your hydroponic solution.  Electrical conductivity is exactly what it may sound like…it’s a measure of how well a material conducts electricity.  This is relevant to your hydroponic garden because hydroponic nutrients are made up primarily of mineral salts, which are a great conductor of electricity.   By measuring EC in your hydroponic solution, you are basically measuring the amount of nutrients that are contained in your hydroponic solution. 

There are limitations to what EC/TDS sensors can measure.  For instance, you can’t measure the amount of individual nutrients that exist in your hydroponic solution with these sensors.  You won’t be able to tell the specific amount of Nitrogen (N), Phosphorus (P), Potassium (K) or other nutrients that exist in your solution.  Sensors that are capable of this cost many hundreds, or even thousands of dollars.  So, unless you’re a professional grower you will probably want to avoid that expense.  Not to worry, though.  Measuring exact amounts of nutrients is not required for the vast majority of us, and here’s why…

N-P-K Ratio:

On each and every hydroponic nutrient solution you purchase, you will see 3 numbers.  These 3 numbers represent you N-P-K (Nitrogen-Phosphorus-Potassium) Ratio.  While your hydroponic fruits and vegetables require more than these 3 elements, these 3 elements (N-P-K) are the most important elements in your nutrient solution.  For the purpose of growing healthy and great tasting vegetables, these are the elements we will focus on in this article.

So why don’t you need to buy an expensive nutrient tester that tells you exactly how much Nitrogen, Phosphorus and Potassium (N-P-K) you need?  It’s because the N-P-K ratio is listed on your hydroponic nutrient solution, and because your fruits and vegetables will generally absorb these in equal amounts.  Personally, my favorite nutrient solution is called MaxiGro.  The MaxiGro nutrient solution ratio is 10-5-14, which is great for growing fruits and vegetables.  More advanced growers may want to have a nutrient solution with more Phosphorus for flowering and fruiting plants, but we’ll save that discussion for another day.  Think of the MaxiGro solution ratio this way…in every scoop of nutrients that you put into your hydroponic reservoir, there will be 10 Nitrogen’s, 5 Phosphorus’ and 14 Potassium’s.  And for every 10 Nitrogen’s, the average fruit and vegetable will absorb approximately 5 Phosphorus’ and 14 Potassium’s.  That means the N-P-K ratio in your nutrient solution stays at 10-5-14, and you don’t need to measure the exact amount of Nitrogen, Phosphorus and Potassium.  A 10-5-14 ratio is about the same as a 2-1-3 ratio, which is what I suggest you use when growing a wide variety of fruits and vegetables.  You can add a solution with additional Phosphorus if you’re growing more fruiting and flowering plants.

Adjusting Your TDS:

Measuring your TDS will produce a reading that tells you how many nutrients are in your reservoir.  More nutrients means that there will be a higher TDS (or EC) reading.  For simplicity, I suggest you break plants up into two categories:

Category 1: Leafy Greens and Herbs – These plants tend to desire lower amounts of nutrients in their hydroponic solution.  You should add nutrients until your meter shows a reading of between 600-1000 TDS.  I suggest using a TDS reading of 800.  One of the exceptions to this rule is Pac-Choi, which prefers a TDS reading closer to 1,200-1,400.  Spinach also likes higher TDS ranges, but tastes quite good at lower ranges as well.

Category 2: Flowering Fruits and Vegetables – Flowering fruits and vegetables like tomatoes, cucumbers and peppers prefer higher nutrient levels, which corelates to higher TDS values.  For these plants to flower and produce fruit, you should focus on creating an TDS range of between 1,500 and 2,000.  This also applies to broccoli, cabbage (not lettuce) and hot peppers, which like to be towards the top end of that TDS range. 

Make sure that after you add nutrients to your hydroponic solution, and before you measure the TDS, you allow the nutrient solution to mix thoroughly with the water in your reservoir.  You can mix them manually, or you can let the pump do all the work by letting it run for 15 minutes after adding the nutrients.  If you do not allow the nutrients to mix properly, your EC measurement will be incorrect.

Adjusting Your pH:

pH is a scale used to specify how acidic or basic your water solution is.  pH is also an incredibly important aspect of your nutrient solution, as the pH level determines how well your plants are able to absorb nutrients. You can control this with your pH sensor and the pH up and down solutions.  These are provided with the iHarvest, or available online.  Keeping your pH between 5.8 and 6.5 will work very well for almost anything you want to grow.  If your pH is below 5.8, add a small amount of pH up and test again.  If your pH is above 6.5, add a small amount of pH down and test again.

Make sure that after you add your pH up or down solution, and before you measure the pH, you allow the nutrient solution to mix thoroughly.  You can mix the solution manually, or you can let the pump do all the work by letting it run for 15 minutes after adding the pH adjuster.  If you do not allow the nutrients to mix properly, your pH measurement will be incorrect.

TDS and pH Balance:

Now that you’ve adjusted your TDS and your pH, it’s time to check your TDS again.  That’s because adjusting the pH can impact your TDS reading, and adjusting your TDS can impact your pH.  Make sure that both measurements are where you want them before you are done.

Maintaining your TDS and pH Balance:

TDS and pH balances can swing back and forth over time.  While you’re beginning to learn hydroponics, I suggest that you check the pH and TDS balance daily.  Over time, this won’t be necessary.  You’ll get a feeling for how often you need to check based on a variety of factors.  For instance, using organic nutrients tends to induce the TDS to swing more often.  And, I’ve found that once a system has been running consistently for a while, it tends to stabilize and you will only have to check it once or twice a week.

Nutrient and pH Chart for Hydroponic Gardens

Plant

pH

EC

PPM

 

 

 

 

Basil

5.5-6.5

1.0-1.6

700-1120

Bean (Common)

6.0-6.0

1.8-2.4

1400-2800

Bean (Broad)

6.0-6.5

1.8-2.4

1400-1800

Bell Peppers

6.0-6.7

1.8-2.8

1400-2000

Broccoli

6.0-6.5

2.8-3.5

1960-2450

Brussell Sprouts

6.5-7.5

2.5-3.0

1750-2100

Cabbage

6.5-7.0

2.5-3.0

1750-2100

Cauliflower

6.0-7.0

0.5-2.0

1050-1400

Celery

6.3-6.7

1.8-2.4

1260-1680

Chives

6.0-6.5

1.8-2.4

1260-1680

Cucumber

5.8-6.0

1.7-2.5

1190-1750

Eggplant

5.5-6.5

2.5-3.5

1750-2450

Lavender

6.4-6.8

1.0-1.4

700-980

Lemon Balm

5.5-6.5

1.0-1.6

700-1120

Lettuce

5.5-6.5

0.8-1.2

560-840

Melon

5.5-6.0

2.0-2.5

1400-1750

Mint

5.5-6.0

2.0-2.4

1400-1680

Pak-choi

7

1.5-2.0

1050-1400

Parsley

5.5-6.0

0.8-1.8

560-1260

Pea

6.0-7.0

0.8-1.8

580-1260

Peas (Sugar)

6.0-6.8

0.8-1.9

580-1261

Peppers (Bell)

6.0-6.5

2.0-2.5

1400-1750

Peppers (Hot)

6.0-6.5

2.0-3.5

1400-2450

Pumpkin

5.5-7.5

1.8-2.4

1260-1680

Sage

5.5-6.5

1.0-1.6

700-1120

Spinach

5.5-6.6

1.8-2.3

1260-1610

Squash

5.0-6.5

1.8-2.4

1260-1680

Strawberries

5.5-6.5

1.8-2.2

1250-1540

Swiss Chard

6.0-6.5

1.8-2.3

1260-1610

Thyme

5.5-7.0

0.8-1.6

560-1120

Tomato

5.5-6.5

2.0-5.0

1400-3500

Watercress

6.5-6.8

0.4-1.8

280-1260

Watermelon

5.8

1.5-2.4

1050-1680

Zucchini

 6.0

1.8-2.4

1260-1680

 

There's more great growing information in the links below:

Let's grow together,

Dave


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