We do not use Mazzei injectors but Dosatrons which run on a little different principal but the set up should be the same. The Mazzei should have a table that gives it's flow rate at a given pressure. From there you need to know how much fertilizer total you want to apply then do a little math to get the concentration of solution you need to mix.

Say you want to put down 5lbs of fertilizer in 1000 gallons of water - how much concentrate do you need? The injector should be rated with an injection rate (say 100:1). That tells you that for every 100 gallons of water you run through the system 1 gallon of solution will be injected.

The formula should be:
Gallons total/injection ratio = gallons of concentrate
1000Gallons total/100 =10 gallons concentrate

Add your 5 lbs of fertilizer to ten gallons of water to make your concentrate. The injector also will have a flow chart for different pressures (say 3 Gallons Per Minute at 8 pounds of pressure). You take your total amount (1000gal water + 10gal concentrate = 1010gal total) and divide by 3GPM. That tells you that it will take 336 minutes to put down the total amount of water you want.

So in this particular problem you want ten gallons of concentrate run through the system for 336 minutes to put 1000 gallons of water with 5 pounds of fertilizer into your system.

It's not a complicated as it looks on the surface - remember the time calculation only works if the total out put of your drip tape run exceeds the GPM of your injector. Unless you have a very short run then it should be greater.

Tom

Thanks that is very close to what I am looking for. I just need to find the rates on the injector I have. It just showed up in a envelope. No documentation or anything. I started navigating mazzei's site. I will figure it out.

One thing I thought of. To figure the area I need to figure just what is under plastic. With my old overhead system we figured the whole lot.

Mazzei has technical info on their website if you know what injector you have.

Tom

Here is a link that might be useful: Mazzei Ag Product Cat

Hey Tom I am trying to figure out the correct amount of water my vegetables need a week.
Do you have a calculation for that.
I have beds 32 in wide, 200 foot long
I still. Haven't figured out my needed fertalizer amounts yet.

Most vegies call for about 1"/week but that varies with different types, the carrying capacity of soil and the amount of rain you get. In a perfect world, 1 inch/acre translates into about .6 gallons per square foot (27,000 GAAC/43,560FTAC). Now I figure that each emitter covers about 1SQFT. We use tape with the emitters on 12" centers so we use the length of a run as the square foot calculation (500 feet of tape = 500 SQFT) but it will vary if you use a different emitter spacing. So take you square foot, multiply by .6 and you should get a rough idea of your rough figure (500SQFTX.6GA=300GA). In theory that gives you 1FTAC coverage. We run .20GPH emitters so 500FT has 500 emitters which means to put out 300GA we need to run the system for three hours (500emittersX.20GPH=100GPH 300GA/100GPH=3HR)That figure can be fudged quite a bit if you have gotten rain in the week or if your soil holds water well. Evaporation also plays a role - more is needed in hot weather than cool, as do row covers and mulch.

All that math being said, we usually use the finger test (if we stick a finger in and it is good and wet down as far as we push it's probably OK. I have often considered getting a flow meter to see exactly how much water is doing down range but they cost so darn much it's not really worth it. There are times I am sure we over water, and others we underwater but in the end if the plants are doing well we call it a success. If we were irrigation hundreds of acres being more precise would probably be economical but for just two or three acres your not loosing too much.

Tom

Here is a link that might be useful: Irrigation formulas

Thanks Tom. I got 2.10 hrs on my one field with .45 gph per 100 foot at 12 ish psi. That will put out little over 500 gal through 1400 feet of drip. If I calculated right that should give us 1 inch of water at each emiter.