Fertilizer Needed
I really like drip irrigation. I also really like fertilizer injectors for the drip irrigation (fertigation). One of the issues I have is knowing how much to use. I like to use water soluble fertilizers such as Miracle Gro, Schultz, and Jack’s. The problem is that these are usually used to mix a gallon at a time, or used in a hose end sprayer. They don’t have any kind of directions for making concentrate to inject into an irrigation system. So I never really know how much fertilizer I am giving my plants.
On the site of JR Peters, makers of Jack’s soluble fertilizer, which I really like, I found this Fertilizer Calculator. It’s a start, and gets you some better information, but I wanted to be able to calculate how much fertilizer I needed for a given amount of water, the concentration of fertilizer in a mix of concentrate, and the gallons of concentrate you can make for a certain package size. I found another site, Greenhouse Product News, which had an article explaining the calculation for given inputs of fertilizer. That article, and more specifically, the downloadable article, gave much better info for calculating fertilizer needed in an injector system.
I took the formulas here and created this spreadsheet for calculating the amount of fertilizer needed, the concentrate, and the gallons.
Fertilizer Concentration Calculator
To use, you simply add a fertilizer type, or if the one you are using is listed, enter the fertilizer analysis, desired concentration and ratio, and you will be given the amount of fertilizer needed. The other tabs will give you concentration of the fertilizer given the amount and ratio used,
Fertilizer Concentration
and the number of gallons of concentrate for a given desired concentration and ratio.
Gallons of Concentrate
I hope you find this useful, and if you have any suggestions, please leave them in the comments.
