20-10-20 for your 200 gallons (757 liters):

[(100ppm)(757liter)]/[(1000mg/g)(20%)]
= 378.5 grams or
= 13.35 ounces

That's 13.35 ounces. Check that the fert has micros and if you must use hard water you're almost surely perfect to go. Even stick in up to a half level teaspoon of boric acid (less than 3 g) and a a dime's worth of Epsom Salt from Walmart if you are really gun ho.

This post was edited by PupillaCharites on Thu, Apr 24, 14 at 14:37

Ok, you think that same formula will work for lettuce and the like?

I need to learn that math, I have a heck of a time making things predictable.

Did you happen to see my water issues in the other thread?

I've got a bunch of fires to put out at the moment so I'll read the other as soon as I can.

Not for lettuce Rio, if that's what you meant. Well, really we don't know, but by defaul;t the tobacco would be no until you can get us an analysis of what's in it from the seller. The assumption for a complete tobacco float fertilizer is that it has very weak micronutrients. Like "Peat Lite" from J R Peters. So this tobacco stuff is loaded with nitrogen which prevents us from using much Calcium Nitrate. Calcium deficiency would be a problem for you doing fast leafies on rainwater. If you want to assume this 20-10-20 tobacco stuff you found is a typical tobacco float formula, you can't avoid paying the piper. Sure it could be used, but then you'd need to work out the calcium issue for rainwater and maybe bump up the phosphate, which is low for tobacco floats. Even though P's not a big problem for leaves, we'd need to look at it and possibly a sack of MKP (so if you can't get that locally - back to where you started by mail), cheap epsom salt and a blend of micronutrients. You could mailorder the blend of micros from JRPeters also, and it is a great deal and small = cheap to ship if that's the issue. Then I'd say look at that product and add the amount that gives 2.5 ppm of iron, so that would determine the amount of the micro blend to use.

It's all about your local vs. shipped economics. The tobacco formula would be a fine base if it was cheap enough and probably could work just fine with the adjustments mentioned. But we need to sharpen out pencils and be sure what your local guy is selling - analysis of it.

Most cheap bulk hydro complete ferts use Fe EDTA. which is great at low pH. I really think the tobacco formula would too. For most this is fine, but in my personal case I like to drift my pH up to 7 for some things and for that I'm a big propmoter of Fe DTPA. No biggie just something I'm noting if you go that route.

Thanks for the reply!

I am actually not raising tobacco in these beds. We are starting our vegatable plants in it.

Tried to order masterblend through Morgan county seeds today. But they can't seem to get it right. Guess I will look at peters.