# Help me with fert math

Discussion in 'Fertilizer Application' started by Fubba, May 29, 2014.

1. ### FubbaLawnSite Senior Memberfrom Middle GAMessages: 360

This is my first year putting down liquid fert. I'm combing two products for a nitrogen and potassium mix. The potassium source also contains some nitrogen. I know how to figure up how much of a product I need to put down in order to get the lbs/sq ft. I do not know how to do this when combining two products. Can anyone help?
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2. ### greendoctorLawnSite Fanaticfrom Honolulu, HawaiiMessages: 10,131

First of all, figure out how much N you want to apply per 1000 sq ft. Then figure out how much K. To keep things simple, my usual mix involves 1 lb potassium nitrate and from 1-5 lb of ammonium sulfate depending on grass type as well as what am I trying to do. Grow ins from plugs or sprigs get more N. Centipede grass is low N. Zoysia is low N also unless it is a grow in.

3. ### RigglePLCLawnSite Fanaticfrom Grand Rapids MIMessages: 13,807

Green is right. Figure out how much potassium you will need to add to the tank. Find out how much nitrogen you have automatically included. Then add your nitrogen carrier to bring it up to the amount needed.
For instance figure it out for 10,000 sqft. Then find the amount of water needed for 10,000 sqft. Then for a full tank.
Then make a fill chart for half a tank, 1/4, 3/4 and so forth. Use Excel and print it out.

You may also wish to let Excel make a fill chart for one bag of KNO3, let it find the amount of water you need to add for one bag--water is easier to measure than a powder.

4. ### lilmarvin4064LawnSite Senior Memberfrom transition-zoneMessages: 757

a lot of times the product will indicate - "contains 3.15 lbs of N per Gallon" (30-0-0) or something similar. So if I want to apply 1/10th of lb of N per 1000, on 10,000 sq ft, I figure (.1 x 10 = 1 lb of N) then, 1 lb n / 3.15 = .317 gallons of product, or (128oz/g x .317) = 40.5 oz of product