Any tips on using natural fertilizers with my fertigation system to grow tomatoes in a greenhouse?

Q:

I’m growing tomatoes in a 430,000 square foot greenhouse. I’m looking for information about bioponics, i.e., using natural fertilizer with my fertigation system.

A:

Natural and organic fertilizers can be used in hydroponics. However, the process is highly technical and comes with a few challenges.

Firstly, obtaining high-quality, concentrated, natural fertilizers for commercial production is much more costly than using chemical fertilizer salts.

Secondly, growers usually have to blend many different sources to get the balance of minerals just right for heavy-feeding crops like tomatoes, and often nutrient deficiencies can become a problem.

Because natural fertilizers are often unprocessed, the system relies on strong microbe populations in the growing media and root zone to carry out mineralization of the organic nutrients to release plant-usable nutrient ions.

This process can strip oxygen from a plant’s root zone under warm growing conditions. Also, natural fertilizers are carbon-based, and as such, can ferment or go bad quickly, and they tend to block up drippers and emitters.

There are, however, a few good natural nutrient products on the market for hydroponic use that have been well-processed and mineralized and suit media-based growing systems (coconut fiber is a good substrate when using natural fertilizers and in organic systems). I advise trialing a number of these to determine which products help your crops grow best in your system.

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Written by Lynette Morgan
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Dr. Lynette Morgan holds a B. Hort. Tech. degree and a PhD in hydroponic greenhouse production from Massey University, New Zealand. Lynette is a partner with Suntec International Hydroponic Consultants and has authored several hydroponic technical books. Visit suntec.co.nz for more information.  Full Bio