Bucket Chemistry 101 Bodie Pennisi, Paul Thomas and Mel Garber 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 This is a photo of the fertilizer stock tank. Concentrated solution is pumped out of it, injected into the water line, and distributed to the plants.

PROPORTIONER A device used in a fertigation system to control the rate of fertilizer applied through the system. This is a proportioner used in a fertigation system to control the rate of fertilizer applied through the system. It is the blue device attached to the green stock tank. The stock tank can vary in size from a 5 gallon bucket to a 2,000 gallon tank.

Fertilizer Injector or Proportioner Stock Fertilizer Tank 1 part stock solution Water line 100 parts of water Injector ratio 1 : 100 Irrigation line to plants

Fertilizer Injector or Proportioner Stock Tank Water line 1 part stock solution 5 gal 25 50 100 200 500 etc. x parts of water Injector ratios 1:50 = 1:100 = 1:200 = 1:500 = 2% 1% 0.5% 1% To get from ratios to percent: (1/50) x 100 = 2% To get from percent to ratios : 100/2%=1:50

Parts per million (ppm) 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: Recommended fertilizer application rate. Example: 8 ounces per 100 gal or 200 ppm nitrogen 2. Fertilizer formulation and analysis. Example: 20-10-20 Injection ratio Example: 1:100 Size of stock tank in gallons Example: 25 gallons

Weight Basis Example: A chrysanthemum grower gets a recommendation to apply 20-20-20 water-soluble 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: Recommended fertilizer application rate. 16 ounces per 100 gal 2. Fertilizer formulation and analysis. 20-20-20 Injection ratio 1:30 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 water-soluble 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: Recommended fertilizer application rate. 150 ppm nitrogen 2. Fertilizer formulation and analysis. 20-10-20 Injection ratio 1:100 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 nutrient x 0.75 150 ppm = 10.0 oz of 20-10-20 per 100 gal 20 % x 0.75 (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 Are You 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% K2O = 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