Fertilizing Hydroponic Gardens
Fundamentals to Follow for Best Success
Fertilizing hydroponics gardens for best success is easy once you read through this quick lesson on how to determine how much fertilizer to apply to your particular type of hydroponic systems or growing method.
Just like different soil types will perform better when you understand how to fertilize a given type correctly, so too are various hydroponic growing methods widely practiced by growers.
In fertilizing hydroponic gardens, the first thing you need to do is identify what type of hydroponic garden you have or want. The most common types of systems we will discuss here are:
Soilless (peat, coco coir mixes)
Hydroponics Substrates (Growstones, Stone Wool)
Aeroponics (little or no substrate)
Water Culture (DWC, RDWC, NFT, etc)
Further in determining how to best fertilize your hydroponic garden is classifying your system as Re-Circulating or Drain to Waste.
For most growers and fertilizing hydroponic gardens, Soilless Mixes like peat or coco based ones are most often Drain to Waste. That means that the water containing the dissolved hydroponic fertilizers is pumped or applied to the growing beds, bags or containers sparingly, typically allowing 10-20% run off each time the nutrients are applied with water.
In Re-Circulating Hydroponic systems, the water containing the nutrient solution is captured and reapplied to the roots, sometimes continuously 24/7 or on a cycled timer which is most common with Drip and Ebb & Flo irrigation systems.
Why is This Important?
Because the physical and chemical characteristics that are attributed to your growing style and system have an influence on how nutrient elements are taken up by your crop.
Yes, you might apply the same strength fertilizer (provided it’s made for hydroponics) the same through any of the above systems, but you are likely to see varying levels of success in doing so. Experienced professional hydroponics growers know that not only is it important to choose a high quality nutrient program, they also know it’s equally important to apply it the right way for their growing system and crop type in fertilizing hydroponics gardens for the highest potential rate of success.
Real Life Fertilizing Hydroponics Gardens Applications
Now, let’s get down to it. Real world working examples on how to apply the same nutrients in the variety of gardens and growing methods we have been discussing above.
As of late, we at Grozine have been trialling a newer hydroponic fertilizer program release called Elite Nutrients. We are pleased to say we have been experiencing great success in a variety of garden types, so we are going to use that as our working example in fertilizing hydroponics garden applications here. This guide applies just as well if you are using General Hydroponics (GH), Rock Nutrients, Emerald Harvest, Advanced Nutrients, Heavy16, Cyco Nutrients or one of the other common brands.
Where to Start
Firstly, have some knowledge of the plant type and strain that you are going to grow. For example is it a lighter feeding plant or a heavy feeder? One isn’t necessarily better than another—it’s all about how you apply fertilizer in your hydroponic garden. At Grozine, we grow Scotch Spearmint in a variety of systems as part of our ongoing research in improving the results for growers producing crops for essential oil yields; amongst many other types of crops. However, let’s use Scotch Spearmint as an example, which takes us to the next step.
Secondly, what phase of growth are we targeting for optimum feeding? The list below that we use for Scotch Spearmint may help if you use electronic meters or pens to read your nutrient concentration.
Propagation & Establishing Plants (0.2-0.6 EC*)
Pre Veg & Early Veg (0.3-1.0 EC)
Veg (0.6-1.2 EC)
Bloom (0.8-1.2 EC)
Peak Bloom (1.0-2.0 EC)
Ripening (0.6-1.2 EC)
*EC (Electrical Conductivity, usually in hydroponics 1.0 EC is equal to 700 PPM (parts per million). Note that EC is universal and that there are at least two different PPM scales commonly used with hydroponic solution measurement instruments (total dissolved solids testers TDS)
Thirdly, which system are we going to be growing in, and will it be recirculating?
Above: Example of a Professional Crop Feeding Program NOTE special propagation schedule for aeroponics/clone machines
How To Apply Hydroponic Nutrients in Different Systems
OK, so based on the above three steps, let’s look at how we would approach fertilizing different hydroponic garden types, assuming the same growing environment and crop type following Elite Nutrients proven crop feeding program.
The best place to start is the Manufacturers General Recommendations. Luckily for us, with Elite this is super easy as they provide a free app to calculate mixing ratios based on the size of your individual reservoir when using the Elite Nutrients App (we downloaded it for free from iTunes HERE).
Here’s a screenshot, based on a 100 Litre reservoir in the first six weeks of the peak bloom stage
Once you know these general hydroponics fertilizer applications rates for your particular crop feeding program, you have a baseline for which you can apply the generalization to various systems we outline below.
Special Note: Complete Feeding Programs (HERE) take the guess work out of what type of nutrient to apply and when—just follow the chart. What we are teaching you here in this article are fundamentals for fine tuning to your preferred crop and growing method. Some growers develop their own programs too using a range of products from a variety of manufacturers; however, this takes trial and error and can cost you yields in the process.
Soilless (Peat, Coco Coir)
Drain To Waste Versus Re-Circulating, apply a little milder than you would with recirculating in drain to waste gardens, maybe less 20% concentration for example. Overtime, nutrients will accumulate in the substrate because they are not getting washed through continuously as they do in recirculating systems.
With Peat Mix or Coco Coir, usually FULL STRENGTH based on manufacturer’s recommendations is fine (feed, feed, water regimen). However, it shouldn’t exceed the target rates we outlined above too greatly—add more fresh water after adding nutrients if necessary until you find the sweet spot when mixing your hydroponics reservoirs.
100% Strength for 100 L
80% Strength for 100 L
Hydroponics Substrates (Growstone, Stone Wool)
Same rule here applies as with above when factoring Drain To Waste versus Recirculating application rates, and that’s use about 20% less strength overall in Drain to Waste.
In hydroponic substrates, the physical properties of the medium (especially with Growstone) have the potential to allow for more air to surround plant roots because the media are designed for growing and are more porous. This means plants don’t have to work as hard to absorb water and nutrients, the plants are working more efficiently on a metabolic level. The chemical properties of these growth media types also make it easier for roots to extract nutrients, for example they don’t have to fight Cation or Anion levels as much (the “magnetism” potential of the substrate particles to hold nutrients)
For Hydroponics Substrates, typically 80% of recommended general hydroponic strength is good, less an additional 15% if recirculating
80% Strength for 100 L
65% Strength for 100 L
Aeroponics (little or no substrate)
We are unfamiliar with any Drain to Waste aeroponic systems widely used. So for our discussion the recommendations here are based on recirculating aeroponics systems.
As with hydroponics, aeroponics systems help more oxygen surround plant roots versus traditional growing methods. Aeroponics systems use sprayers to infuse air from the atmosphere into the nutrient rich spray that is continuously or intermittently misted through a root chamber that supports the bare root plants.
Typically for Veg and Bloom purposes, using nutrients at around 60% of the recommended hydroponic nutrient strength is a good rule of thumb for aeroponics unless the manufacture gives specific directions for aeroponics use (Elite Nutrients DOES have such a recommendation for aerocloning HERE)
Water Culture (DWC, DFT, RDWC, NFT, etc)
These types of setups most often Recirculate the nutrient solution (DWC is the exception) and utilize very little or no growing media, ie Water Culture, roots are surrounded by nutrient rich water and air.
What DOES differ amongst these types of systems is the level of aeration and the amount of Dissolved Oxygen (DO) the solution may contain.
In our experience, DWC (Deep Water Culture), DFT and NFT systems offer increased aeration levels over conventional soilless growing practices. As a result, lower nutrient concentrations versus general recommendations usually perform very well, typically at around 60% to 75% of full strength.
RDWC (Recirculating Deep Water Culture) systems like the ones we operate in our greenhouse may operate at SuperCharged Dissolved Oxygen levels. Approximately 1.0L of air per minute per 4.0L of solution volume helps put growth rates into the “supercharged” growth bandwidth.
When growing crops in the Supercharged O2 Bandwidth, only unusally low levels of hydroponic fertilizer are needed or recommended. At these higher levels, growth rates are actually stronger at considerably lower concentrations versus higher. Only 25%-50% strength from full strength is recommended here in fertilizing hydroponic gardens.