Mixing liquid fertilizers safely
It is not recommended to apply dry fertilizer to woody ornamentals after Aug. 1, for fear the resulting new growth will not have sufficient time to harden and will be killed by the first frost in October.
Liquid fertilizer can be applied up until Sept 15. It is readily available for plant uptake and new growth should have plenty of time to harden off before frost . How to mix it is a common question. It is usually applied too strong. We usually prefer to make the calculations based on the parts per million of nitrogen.
I need to know the age of the crop (seedling or 2 years old), the size tank used, or the size of the stock tank used with a proportioner, the ratio and the fertilizer analysis used and if it is desired to feed with each irrigation, weekly or merely spray the foliage in order to provide the amount to use.
The amount of dry (to be dissolved in water) fertilizer must be weighed. We generally will choose a ppm between 100 and 200 to be safe.
The amount could be a few grams for a backpack or ounces or possibly pounds. 100 ppm of a 20 percent nitrogen fertilizer requires only 6 grams or roughly 1.5 teaspoons per 3 gallon backpack.
A 200 ppm solution using 20-20-20 would require 13.33 ounces by weight in 100 gallons of water. 150 ppm would require 10 ounces by weight. 100 ppm would require 6.66 ounces by weight in 100 gallons of water.
A Hozon is a simple, inexpensive proportioner that attaches to a water faucet before the garden hose. It has a tube that is dropped into the stock tank (a 5 gallon bucket is commonly used) that is placed beside the faucet. As the water is turned on, the fertilizer solution in the bucket is pulled into the hose by the suction created by the water flow from the faucet.
The Hozon is a 1 to 15 ratio. It is not adjustable. For every 15 gallons of water that passes though the Hozon, it will pull 1 gallon from the bucket.
To apply a 100 ppm solution using a 20 percent nitrogen fertilizer, add 1 ounce by weight of the fertilizer for each gallon of water in the stock tank; (1.5 oz for 150 ppm or 2 oz for 200 ppm). Add 5 oz by weight to 5 gallons in the stock tank for 100 ppm when using a Hozon.
I have a table I can fax for more expensive proportioners with different ratio settings; different nitrogen percents, etc.
Amounts are based on the maturity of the crop, what other fertilizer is present, how it will be applied and frequency. Small amounts can be added at each watering the entire growing season if desired. The key word here is small.
200 ppm can be applied to the foliage occasionally by sprayer to give a crop a little boost. I am not sure it is as beneficial as many assume, but they feel better. The best boost would be to water the roots with it.