Bucket Chemistry 101
Bodie Pennisi, and Paul Thomas
Extension Horticulture Specialists
The University of Georgia
Bucket Chemistry
Fertilizer Problems Are
Not That Bad !
The Way To Tackle
Them Is …
Greenhouse Crops and
Fertilizer
Recommendations
Fertilizer Stock Tank
PROPORTIONER
A device used in a
fertigation system to
control the rate of
fertilizer applied
through the system.
Fertilizer Injector or Proportioner
Stock
Fertilizer
Tank
1 part
stock
solution
Injector ratio
1 : 100
Water line
100
parts of
water
Irrigation line to
plants
Fertilizer Injector or Proportioner
Stock Tank
1 part
stock
solution
5 gal
25
50
100
200
500 etc.
To get from ratios to percent:
(1/50) x 100 = 2%
To get from percent to ratios :
100/2%=1:50
Water line
x parts of water
Injector ratios
1:50 =
1:100 =
1:200 =
1:500 =
2%
1%
0.5%
.01%
Fertilizer recommendations for greenhouse
crops are given as either ppm of a specific
fertilizer nutrient or in pounds and ounces
(weight basis) of a fertilizer formulation per 100
gallons of water
Parts per million (ppm)
One part of a substance into one million
parts of another substance
Things You Need To Know To Solve
ppm Problems:
1. Recommended fertilizer application rate.
Example: 8 ounces per 100 gal or 200 ppm nitrogen
2. Fertilizer formulation and analysis.
Example: 20-10-20
3. Injection ratio
Example: 1:100
4. Size of stock tank in gallons
Example: 25 gallons
Weight Basis
Example: A chrysanthemum grower gets a
recommendation to apply 20-20-20 watersoluble formulation to a final concentration of 16
oz per 100 gallons of water.
How much fertilizer should be mixed in a 25 gallon
stock tank if an injector with a 1:30 injection ratio
will be used?
Things You Need To Know To Solve
This Problem:
1. Recommended fertilizer application rate.
16 ounces per 100 gal
2. Fertilizer formulation and analysis.
20-20-20
3. Injection ratio
1:30
4. Size of stock tank in gallons
25 gallons
Solution
Step 1: Adjust the rate for the stock tank size using the
following equation:
Equation 1
oz per 100 gal
= oz fertilizer per stock tank
100 / Stock Tank Size (gal)
16.0 oz per 100 gal = 4.0 oz of 20-20-20
100 / 25 gal
Solution
Step 2: Adjust the rate for the injection ratio:
Equation 2
oz per stock tank x injector ratio =
oz per stock tank using injector
4.0 oz per 25 gal x 30 =
120.0 oz per 25 gal @1:30 ratio
Commercial Fertilizer (ppm)
Example: A pansy grower gets a
recommendation to apply 150 ppm
nitrogen using 20-10-20 watersoluble formulation.
How much fertilizer should be mixed in
a 25 gallon stock tank if an injector
with a 1:100 injection ratio will be
used?
Things You Need To Know To Solve
This Problem:
1. Recommended fertilizer application rate.
150 ppm nitrogen
2. Fertilizer formulation and analysis.
20-10-20
3. Injection ratio
1:100
4. Size of stock tank in gallons
25 gallons
The Rule of 75
1 oz / 100 gal = 75 ppm
HOW DID WE GET THIS ?
One ounce (28 grams) of any pure dry substance
that will dissolve 100% in a volume of 100 gal
equals 75 ppm
1 oz = 28 g or 28,000 mg
28,000 mg ÷ 379 L = 73.88 ppm
( 1 gal = 3.79 L 100 gal = 379 L )
Solution
Step 1: Convert the ppm recommendation to a weight
basis using the following equation:
Equation 3
desired ppm = oz fertilizer per 100 gal
% of fertilizer x 75
150 ppm
20 % x 75
= 10.0 oz of 20-10-20 per 100 gal
(final solution)
Solution
Step 2: Use equation 1 to adjust for a stock tank size of
25 gallons:
oz per 100 gal
= oz fertilizer per tank
100 / Tank Size (gal)
10.0 oz per 100 gal = 2.5 oz of 20-10-20 per 25 gal
100 / 25 gal
Solution
Step 3: Use equation 2 to adjust the rate for a 1:100 injection
ratio: (In other words, concentrate it! )
oz per stock tank x injector ratio =
oz per stock tank using injector
2.5 oz per 25 gal x 100 =
250.0 oz per 25 gal using a 1:100 injection ratio
Solution
Step 4: Convert ounces to pounds and ounces where:
16 ounces = 1 pound (dry)
250.0 oz per 25 gal = 15 lbs 10 oz 20-10-20
16 oz /lb
(. . . .in a 25 gallon stock tank)
This will give you 150 ppm with a 1/100 ratio
You Are Done !
Not Yet !
How many parts per million of actual phosphorus and
potassium will be applied with the 150 ppm N from the
20-10-20 ?
Equation 4:
Oz fertilizer per 100 gal x 0.75 x percent nutrient =
the ppm desired nutrient .
Phosphorus 10.0 oz per 100 gal x 0.75 x 10% P2O5
= 75 ppm P2O5
Not Yet !
For actual phosphorus :
P2O5 is actually only 44% elemental phosphorus
Therefor
75 ppm P2O5 x 0.44 = 33 ppm actual phosphorus
Equation 4 – Now lets find the potassium true value!
Oz fertilizer per 100 gal x 0.75 x percent nutrient
= ppm desired nutrient
Potassium 10.0 oz per 100 gal x 0.75 x 20% K 2O
= 150 ppm K2O in solution
For actual potassium : K2O is 83% elemental potassium
150 ppm K2O x 0.83 = 124.5 ppm actual potassium
Final analysis:
150 ppm N : 33 ppm P : 124.5 ppm K
A Test !
A poinsettia grower needs to apply 500 ppm
nitrogen using ammonium nitrate (33.5-0-0).
He also needs to treat his crop with 100 ppm
magnesium using Epsom salts (10% magnesium).
How much of each fertilizer must be added to a 5
gallon stock tank for delivery through a 0.4%
injector?
If You Got These Answers
You Were Right!
15 lbs 9 oz NH4NO3
and
10 lbs 6 oz MgSO4
Things You Need To Know To Solve
This Problem:
1. Recommended fertilizer application rate.
500 ppm nitrogen and 100 ppm magnesium
2. Fertilizer formulation and analysis.
33.5-0-0 and 10% magnesium
3. Injection ratio
0.4%
4. Size of stock tank in gallons
5 gallons
Solution
Step 1: Convert the recommendation for nitrogen ppm to a weight basis :
500ppm
= 19.9 oz of 33.5-0-0 per 100 gal (final solution)
33.5 % x 75
Step 2: Adjust for a stock tank size of 5 gallons:
19.9 oz per 100 gal = 0.995 oz of 33.5-0-0 per 5 gal
100 / 5 gal
Step 3: Adjust the rate for a 0.4% injection ratio:
0.4% injection ratio is 1:250 (100/ 0.4 = 250)
0.995 oz per 5 gal x 250 = 248.75 oz per 5 gal using 1:250
Step 4: Convert ounces to pounds and ounces:
248.75 oz per 50 gal = 15 lbs 9 oz 33.5-0-0 per 5 gal for 500 ppm N
16 oz
Solution
Step 5: Convert the recommendation for magnesium ppm to a weight basis :
100ppm
= 13.3 oz of 10% Mg sulfate per 100 gal (final solution)
10 % x 075
Step 6: Adjust for a stock tank size of 5 gallons:
13.3 oz per 100 gal = 0.665 oz of 10% MgSO4 per 5 gal
100 / 5 gal
Step 7: Adjust the rate for a 0.4% injection ratio:
0.665 oz per 5 gal x 250 = 166.25 oz per 5 gal using 1:250 injection ratio
Step 8: Convert ounces to pounds and ounces:
166.25 oz per 50 gal / 16 oz = 10 lbs 6 oz 10% Epsom salts per 5 gal for 100 ppm Mg
Nursery Crops and
Fertilizer
Recommendations
Application of Granular Fertilizer
to Container Nursery Crops
Recommendation: Apply 3 lbs of nitrogen per
cubic yard of medium per growing season.
Nursery Response: How much Nutricote (17-6-8)
do I apply to each container of my Hollies in
Trade 1-size containers ?
Things You Need To Know To Solve
This Problem:
1. Recommended fertilizer application rate.
3 lbs nitrogen per cubic yard
2. Fertilizer formulation and analysis.
17-6-8
3. Container size
Trade 1
4. Number of containers per cubic yard
300
Useful Conversions
Pounds Nitrogen/Acre/Year are converted to
lbs fertilizer/A/Yr by the following formula:
lbs N/A/Yr x 100 constant = lbs fertilizer/A/Yr
% fertilizer
Pounds Nitrogen/cubic yard/Year
are converted to lbs fertilizer/ cubic yard /Yr
by the same formula:
lbs N/cu yd/Yr x 100 constant = lbs fertilizer/cu yd/Yr
% fertilizer
Solution
Step 1: Convert the pounds nitrogen recommended to pounds of Nutricote (17-6-8):
3 lbs N/cubic yard x 100 = 17.65 lbs Nutricote per cubic yard
17
Step 2: Calculate pounds of Nutricote per #1 container.
Remember that there one cubic yard of medium can fill up 300 Trade 1 containers:
17.65 lbs = 0.0588 lbs Nutricote per Trade 1 container
300
Step 3: Convert pounds to grams and grams to tablespoons:
1 lb = 453.6 grams
1 tbs = 15 grams
0.0588 lbs x 453.6 = 26.69 grams
26.69 grams / 15 = 1.78 tbs Nutricote
Final answer: 2 tbs of Nutricote per Trade 1 Holly per season
Other Useful Conversions
Milligrams per liter equal ppm
mg/L = ppm
1 gram = 1,000 ppm
1 % = 10,000 ppm
Tank
Mixes
Tank Mixes
Example: A grower wants to prepare a tank
mix containing 200 ppm actual nitrogen
and 200 ppm actual potassium using
calcium nitrate (15.5-0-0) and
potassium nitrate (13-0-44).
How much of each fertilizer must be added
to a 50 gallon stock tank for delivery
through a 1:100 injector?
Things You Need To Know To Solve This
Problem:
1. Recommended fertilizer application rate.
200 ppm nitrogen and 200 ppm potassium
2. Fertilizer formulation and analysis.
calcium nitrate (15.5-0-0)
potassium nitrate (13-0-44)
3. Elemental nutrient analysis.
4. Injection ratio
1:100
5. Size of stock tank in gallons
50 gallons
Note: When combining two or three
fertilizers to formulate a tank mix, it is
usually easiest to start with a fertilizer
containing two nutrients of interest, usually
phosphorus or potassium, and do the
calculation for nitrogen last.
Solution
Start with the potassium nitrate because it contains
both nitrogen and potassium. Since K2NO3
contains 13% actual nitrogen and 44% K2O, first
calculate the amount of K2NO3 to add to 100
gallons to get 200 ppm actual potassium. However,
44% is not actual K, it is K2O.
Step 1: Convert 44% K2O to actual K. Contains
83% actual K :
44 % K2O potassium nitrate x 0.83 = 36.52%
actual K
Solution
Step 2: Determine ounces per 100 gallons of K2NO3
for 200 ppm actual potassium using equation 3:
200 ppm
= 7.3 oz of 13-0-44 per 100 gal
36.52 % x 0.75
(final solution)
Solution
Step 3: But wait … how much nitrogen was added?
Calculate by using equation 4.
7.3 oz per 100 gal x 0.75 x 13% N
= 71 . 175 ppm actual N
So a solution containing 7.3 ounces potassium
nitrate per 100 gallons is 200 ppm potassium
and 71.175 ppm nitrogen.
Solution
Now adjust the amount of potassium nitrate for the stock
tank size and injector ratio.
Step 4: Using equation 1 to adjust for a stock tank size of
50 gallons:
7.3 oz per 100 gal = 3.65 oz of 13-0-44 per 50 gal
100 / 50 gal
Step 5: Using equation 2 to adjust the rate for a 1:100 injection ratio:
3.65 oz per 50 gal x 100 = 365.0 oz per 50 gal @ 1:100 injection ratio
Solution
Step 6: Convert ounces to pounds and ounces:
365.0 oz per 50 gal = 22 lbs 13 oz 13-0-44 per 50 gal for 200 ppm K
16 oz
Solution
Step 7: Calcium nitrate (15.5-0-0) contains 15.5% nitrogen and
200 ppm total nitrogen is required.
However, the potassium nitrate supplied 71.175 ppm N.
Therefore, subtract 71.175 from 200 and apply equation 3:
200 – 71.175 ppm = 11.1 oz of 15.5-0-0 per 100 gal
15.5% x 0.75
(final solution)
Step 8: Use equation 1 to adjust for a stock tank size of 50 gallons:
11.1 oz per 100 gal = 5.55 oz of 15.5-0-0 per 50 gal
100 / 50 gal
Solution
Step 9: Using equation 2 to adjust the rate for a 1:100 injection ratio:
5.5 oz per 50 gal x 100 = 555.0 oz per 50 gal using
1:100 injection ratio
Step 10: Convert ounces to pounds and ounces:
555.0 oz per 50 gal / 16 oz =
34 lbs 11 oz 15.5-0-0 per 50 gal for 200 ppm N
Now You Are Really Done !