SOLUBILITY OF FERTILIZER MATERIALS

There are several instances when it may become necessary to apply fertilizer materials in solution.  Solubility of materials is an important factor in preparing foliar sprays or starter fertilizer solutions.  Some chemicals have low solubility's and hot water may be needed to get them dissolved.

Solubility in Cold Water

Material

 (lb/100 gal)
Primary Nutrients
Ammonium nitrate 984
Ammonium sulfate 592
Calcium cyanamide Decomposes
Calcium nitrate 851
Diammonium phosphate 358
Monoammonium phosphate 192
Potassium nitrate 108
Sodium nitrate 608
Superphosphate, ordinary 17
Superphosphate, triple 33
Urea 651
Secondary and Micronutrients
Ammonium molybdate Decomposes
Borax 8
Calcium chloride 500
Copper oxide Insoluble
Ferrous sulfate 242
Foliarel 123 @ 68oF
Magnesium sulfate 592
Manganese sulfate 876
Sodium chloride 300
Sodium molybdate 467
Solubor 79 @ 68oF
Zinc sulfate 625

Source: O.A. Lorenz & D.N. Maynard. 1980. Knott's Handbook for Vegetable Growers.  (2nd edition.) John Wiley & Sons, Inc., New York.

 

Calculating Parts Per Million

From the Texas Greenhouse Management Handbook

Greenhouse growers frequently express the concentration of fertilizers, in terms of parts per million (ppm).  This unit of measure is relatively unique to the greenhouse industry and often there is some confusion on how ppm is calculated.  The following is a "simplified" formula suitable for most green-house applications.

I. To calculate the ppm contained in 1 ounce of material first solve for B:

A x 75 = B

A = the % active ingredient (AI) in the fertilizer

B = ppm contained in 1 ounce of the material in 100 gallons of water

Example:  Calcium nitrate contains 15% N (0.15 x 75 = 11.25).  If 1 ounce of calcium nitrate is dissolved in 100 gallons of water the solution will contain approximately 11.25 ppm N.

II. To calculate the number of ounces of material required to make up a desired ppm concentration solve for C:

C = Desired ppm conc. / B

B = ppm contained in 1 ounce of the material in 100 gallons of water (from above).

C = number of ounces of material to add to 100 gallons of water to achieve the desired concentration.

Example:  To make up a 250 ppm solution of calcium nitrate first multiply the AI x 75 (.15 x 75 = 11.25).  Next divide the desired concentration by 11.25 (250/11.25 = 22).  To make up a 250 ppm solution of calcium nitrate you would add 22 ounces to 100 gallons of water.

Practical Examples

I.  Make up a nutrient solution of 300 ppm N.   Half of the N to be supplied by ammonium nitrate and 1/2 calcium nitrate dilute 5 and 13 ounces respectively in 100 gallons of water.

II.  Make up a 200 ppm solution of ammonium nitrate for use with a 1:100 proportioner.

.33 x 75 = 29.75

200/29.75 = 7 ounces of ammonium

7 x 100 = 700 to adjust for proportioner

To make up a 200 ppm solution of ammonium nitrate for use with a 1:100 proportion dilute 700 ounces of material in 100 gallons of water.

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