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Ask Erik: Grand Master Debaters - Organics Versus Hydro, Another Perspective

Erik Biksa gets to the bottom of an important debate in the latest edition of Ask Erik. Erik Biksa gets to the bottom of an important debate in the latest edition of Ask Erik.


Q: Dear Erik, I’ve heard all the arguments about hydro versus organic. We grow hydro because growth rates and yield are great, plus the system uses grow rocks in pots on drip trays. The bonus is everything is totally reusable. We pull out the old roots, clean up the rocks, sterilize the system and plant again. We can flip the room from harvest to planting in a day or two — within hours if we want to.

We have had a few issues, however, usually when it comes to adding organic supplements. We do our own custom feeding program. It seems when we add organics, we run into problems. I know the garden can benefit from the ingredients in them. Any advice?



There are a lot of beneficial ingredients in organic and bioactive products that can assist crops in a number of ways, including faster growth, bigger yields and better quality. The trick is the delivery system. In soil-based systems the delivery is natural, as the beneficial microbes and enzymes in the soil occur naturally in similar conditions.

In hydro, the variables for the delivery of the organic ingredients change: The substrate is different, and if the reservoir is re-circulated or premixed and used for several days, the microbes need to learn to swim and are bathed in oxygen-rich conditions. Couple that with warm grow room temperatures and you can get population explosions in some types of microbes versus others, leading to imbalances in the growing system that can potentially lead to other problems.

If you are using a finer grade of grow rock it will retain enough moisture for drain-to-waste applications to be efficient. If a doser system is used or the reservoir is mixed daily and not left to stand aerated, you stand a much better chance of creating the right environment for balanced biochemistry in the plant’s root zone. If you have coarser grow stones already in the system, consider mixing in up to 50% coco coir. This will help retain moisture and further provide substrate for colonization by all the healthy factors you need for success with organics in a hydro system.
A big part of your success will also depend on the nature of the products you want to add. Highly-refined organic and bioactive ingredients are preferred over raw-type organic ingredients for use in hydroponics systems.

Kelp is a great example. More crudely refined kelp extracts are going to impart organic matter into your hydro system. While tolerable in smaller quantities, having this stuff floating around in a warm, highly-aerated reservoir can lead to problems. As further decomposition of the ingredients occurs, changes to the nutrient chemistry can lock out nutrients or cause drastic pH swings.

If you add some microbes and less-refined sources of carbohydrates, like molasses-based products that act as a food source, things will get really out of hand. Adding raw carbs with organics in hydro is like throwing gas on the fire.

There are some really well-engineered crop-feeding programs out there that already take all this into account, in case you prefer not to take as many chances when your investment is on the line. Starting with one of the more basic products is a good idea with hydro systems. If all works as planned, keep working your way up the chart, adding more products as you go along.


Erik Biksa

Bonus Tip:
Sometimes the tasty organic ingredients you want to deliver to your plants can be applied through foliar sprays. Bypassing the root system, reservoir and growing medium means a more direct approach with fewer potential bumps in between.


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Last modified on Wednesday, 26 September 2012 12:55

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