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Nutrient solution

April 30th, 2012 · No Comments

Today I bit the bullet and mixed up some nutrient solution for our plants. Emily has been mixing 20-20-20 in a 35 gallon trash can and watering with a submersible pump. I wanted to get the plants exactly what they need so I’ve done a bunch of research on the most nutritious formulations. Obviously I want to get succulent, flavorful strawberries, but I also want beautiful, luxuriant flower baskets full of vibrant color. From my research, it appears that NPK will grow plants but the micronutrients are important for high brix. Calcium being very important. Boron can be limiting either way: too much and it is toxic; too little and the plants cannot take up Calcium.

Anyway, at Larry Harris’s recommendation, I purchased some fertilizer from Hydrogardens — a special strawberry mix. Unfortunately, it has not arrived yet. I got some Grow More from Alaska Mill and Feed but it does not have the same mix of nutrients as the strawberry formula.

A few late nights researching on the internet and in my hydroponics books and I discovered a handy tool: hydrobuddy. It is written by a chemist and available for free, open-source download at http://scienceinhydroponics.com/
With the help of that program and my reference books to help me figure out the molar weight of some of my chemicals, I came up with a formula that approximates the Hydrogarden Strawberry formula.
I have a 10′ x 12′ x 4′ tank and filled it with snow meltwater. I made a spreadsheet to calculate how many gallons per inch. 37.5″ deep calculated to 2805 gallons.
In that, I mixed 12 lb of Calcium Nitrate (solution grade) 7 lb of Epsom Salts, 7 lb of Grow more, 1 oz of chelated Iron (EDTA). My formula was short on Potassium (K) and I had some KOH left over from a previous year. Hydrobuddy calculated that I needed 3.5 lb of KOH to get the levels of K I wanted. Unfortunately, KOH is very Alkaline so I only put in about 1.5 lb because I was afraid of raising the pH too much. The goal was 6.5 to 6.8 pH. 1.5 lb of KOH brought the pH about 7.5. I added 2/3 of a gallon of General Hydro pH down (which is primarily phosphoric acid according to the label) and that brought the pH down to about 6.6. My Horiba EC meter measured the EC at 1.15mS/cm.

According to Hydrobuddy, this batch of nutes has the following concentrations in ppm
N (NO3-) 79
N (NH4+) 12
P 55
K 85
Mg 30
Ca 87
S 39
Fe 0.6
Zn 0.15
B 0.06
Mn 0.15
Cu 0.15
Mo 0.001

I need about two or three times as much K so I’ll have to get more pH down or some sulfuric acid to be able to use the KOH

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