Throughout my years of being involved in tower farming, I have been asked repeatedly by potential customers about our challenges with pH and EC, when managing hundreds/thousands of individual reservoirs, versus just one central reservoir, as its commonly used in conventional hydroponics.

As I was recently being questioned by a hydroponic farmer at the AgraME (agricultural trade show in Dubai) regarding this subject, I realized that I was not qualified to respond eloquently, at least not scientifically. I could not just answer “we do not experience such problems with a Tower Farm!”, although this has been my experience running a Tower Farm for years without EC nor pH problems! In fact, in spite of years of being involved with Tower Farms (indoors and outdoors), I rarely experienced pH discrepancy nor EC problems. Realizing that the EC and pH control were amongst some the main challenges involved in hydroponics and aquaponics, and in light of my technical ignorance on the subject, I asked Tim Blank, the genius horticulturist who invented and conceptualized the Tower Farm technology by Tower Garden®. So here is what he responded to me:

Comparing managing the pH and EC (electrical conductivity) of a Tower Farm’s individual sumps versus a hydroponic system operating with a central reservoir:

We do guide the conductivity range, but we do it a bit differently than a central reservoir system.

CENTRAL RESERVOIR: This is how a central reservoir works and why it is different or a bit more challenging than a Tower Garden Reservoir. Let’s use a channel system as an example.

• Conductivity and pH have acceptable ranges, and growers attempt to set best pH and Conductivity points on a reservoir controller.
– It doesn’t mean pH and conductivity tolerances can be less or greater, they actually are.

• There is generally thousands of plants sharing one sump, so the ration of water per plant is WAY less than the Tower Garden.
– This means that conductivity, pH, and temperature can move extremely quickly, sometimes within an hour.
– So without constant sensing and dosing, these sumps can leave an acceptable range quickly.
– Lower grade fertilizers can accentuate this process.

• Over time, the minerals get out of balance and build up, skewing the actual elements in the conductivity the plants need. These reservoirs get flushed at periodic intervals.

• Of course root pathogens ultimately infect these systems and stress will reduce growth time or ultimately kill the crop when environmental pressures are extreme.

TOWER GARDEN: Our water to plant ratio is much higher, so pH and conductivity move much much slower, so constant management is not required. We can adjust the dosers for pH and conductivity as needed as they need adjustment. Our mineral blend plant food is made from clean and quality products and generally provides a wider range for pH and conductivity.

Even though the reservoirs are separate, they generally move in tandem for both pH and conductivity. This is why we recommend flushing with similar time intervals.
It is important to remember that “the proof is in the pudding” we have many farms that set to the seasonal setting below, and produce tremendous crops without ever flushing sumps for a half year.

Our entry level grower simply sets the dosers according to seasonal conductivity needs

• Winter – general guidelines for use: set doser dilution ration to 1:200

• Spring – general guidelines for use: set doser dilution ration to 1:300

• Summer – general guidelines for use: set doser dilution ration to 1:400

• Fall – general guidelines for use: set doser dilution ration to 1:300

*Doser settings can be fine-tuned according to specific region, environmental conditions, and desired nutrient solution conductivity.

*Full strength solution is at 1:200 and typically desired during cooler months. As temperatures increase, the solution becomes more diluted up to 1:400 during summer as plant transpiration has increased significantly.
These setting keep conductivity in an acceptable range.
Like the central reservoir it can be good to flush the sumps every couple of Months.

**Our more advance growers will sample from a dozen random TG reservoirs every 2 to 3 days.
This data allows them to fine tune nutrient strength and pH delivery at the dosers feeding the gravity sump.
BIG Benefit: Root pathogens do not spread in our system thus protecting the crop at anytime of year.

BELOW IS OUR GENERAL GUIDELINES HANDOUT.

Conductivity Guidelines for Tower Garden ®

Conductivity is a reference of how weak or strong the mineral content is in your Tower Garden sump. This document provides basic guidelines for maintaining optimal conductivity ranges.

Conductivity meters read in different ranges and the 2 most common would be the following:
Single numbers with decimals. EXAMPLE: 1.0
A meter that reads out in greater detail. 1,000 on this type of meter is the same as 1.0. (Both types of readings are referenced below)

Conductivity is very much influenced by water quality. The more minerals that are in the water supply, the quicker conductivity will increase in the Tower sump. Many growers exceed these ranges recommended below and still maintain tremendous success in growing.
A key visual indicator that conductivity may be building up too much, is strong wilting of the leaves during brighter daylight hours. Crops outdoors under direct sun will wilt faster and require a lower conductivity than the exact same crops growing in a greenhouse.

NOTE: this same type of wilting can occur from 3 other things:

1. Wilting after a period of prolonged cloudy weather.
2. Wilting from high relative humidity that is often experienced in the southeast summers.
3. Wilting from mild or severe root disease preventing the uptake of water at a high volume.

DOSER SETTING GUIDELINES:

• Winter – general guidelines for use: set doser dilution ration to 1:200

• Spring – general guidelines for use: set doser dilution ration to 1:300

• Summer – general guidelines for use: set doser dilution ration to 1:400

• Fall – general guidelines for use: set doser dilution ration to 1:300

Doser settings can be fine-tuned according to specific region, environmental conditions, and desired nutrient solution conductivity.

Full strength solution is at 1:200 and typically desired during cooler months. As temperatures increase, the solution becomes more diluted up to 1:400 during summer as plant transpiration has increased significantly.

CONDUCTIVITY RANGES:

Winter/Cold Season:

Utilize a full strength fertilizer solution (20/mls per gallon of water – doser setting 1:200) = Conductivity of 2.3/2,300 (conductive reading will change slightly with various water sources).

Using a central reservoir features great advantages. However, its nutrient solution constantly needs to be tweaked in order to offset the variation of pH and EC and pathogens contaminations. This is truly something that we do not experience indoors at True Garden, our Tower Farm in Arizona, nor do we have these problems outdoors at Ibiza Farm, in Spain. I do understand now that Tower Garden’s advantage mainly has to do with a superior ratio of water and nutrients per plant in comparison to working with a central reservoir. I do also understand that we benefit from the purity of our mineral blend which we use as fertilizer. Anyway, in a less scientific way, I can only tell anyone concerned about this subject not to worry about it! Our fully automated aeroponic Tower Farms systems have been around for over a decade! We are not in the test mode of development! Tower Garden technology is not in its inception phase of development. We have profitable Tower Farms with as little as several dozen towers and others featuring several thousands of towers. In comparison to hydroponics, running an aeroponic Tower Farm greatly reduces the problems of electrical conductivity and pH fluctuations. In other words, it also reduces the labor involved in managing a commercial Tower Farm in comparison to hydroponic farm.