3/20/13&

1&

Brian Whipker

How Fertilizer Formula Influences Plant Growth

N"

Fer&lity"Rate"

P" K"

What"key"nutri&onal"factors"

influence"plant"growth?"

Understanding a Fertilizer Bag

Acidic"or"

basic?"

Nitrogen"

form?"

Mixing?"

EC"check"

values?"

Contains"P,"

Ca,"Mg,"micros?"

Fer&lizer"

sources?"

Understanding Nitrogen

Type%

Bag%%%NO3-N%

Bag%%%NH4-N%

Bag%%%

Urea%

Total%%%NO3-

N%

Total%%%NH4-N%+%Urea% Total%%%

NH4-N%Total%%%Urea%

20-20-20% 6.11$ 3.89$ 10.0$ 30.5%$ 69.5%$ 19.5%$ 50.0%$

20-10-20% 12.06$ 7.94$ 0.0$ 60.3%$ 39.7%$ 39.7%$ 0.0%$

15-5-15% 11.75$ 1.20$ 2.05$ 78.3%$ 21.7%$ 8.0%$ 13.6%$

13-2-13% 11.9$ 0.3$ 0.8$ 91.6%$ 8.4%$ 2.3%$ 6.1%$

Nitrogen"Form&

Prefer">80%"as"Nitrate"N"

NH4NN+Urea"boost"growth"

Avoid"excess"NH4NN+Urea"with"cold"temperatures"

•  Description: Yellowing (chlorosis) – Use of only

NH4-N based fertilizers (20-20-20)

– Plants grown cold (50F nights)

Leaves&–&En/re&Plant&

Ammonium&nitrogen&toxicity&

Ini&al"•  Description:

Yellowing (chlorosis) – Use of only

NH4-N based fertilizers (20-20-20)

– Plants grown cold (50F nights)

Leaves&–&En/re&Plant&

Advanced"

Ammonium&nitrogen&toxicity&

3/20/13&

2&

Understanding a Fertilizer Bag

•  P is an essential element – Target 5 to 10 ppm in substrate – P is the primary contributor to plant stretch

Is"Phosphorus"(P)"provided?"

Understanding Phosphorus

Phosphate"vs."Compactness"P2O5&as&a&%&of&N&in&postCplant&fer/lizer&

P2O5&=&50%&of&N& 15%& 7.5%& 0%&(e.g.&20C10C20)& (13C2C13)&

Source:"Paul"Nelson,"NCSU"

Phosphorus Deficiency: Lower Leaf Purpling

Brian"W

hipker"

Phosphorus Deficiency: Lower Leaf Spots

Brian"W

hipker"

Brian"W

hipker"

NP"

NP"

NP"

P"Deficiency:"Leaf"spo[ng/yellowing"Gerbera%growth%as%fertilization%rate%increases%

(in%ppm%N)%

&50""""""""""""75"""""""""""100"""""""""""200""""""""""""300""""""""400&

K. Yeon Jeong, B. Whipker, I. McCall, and J. Frantz!

Brian"W

hipker"

Understanding&Fer/lizer&Rates&

3/20/13&

3&

•  Description: Lower leaves with total leaf yellowing

Nitrogen&Deficiency&

Nitrogen"Deficiency"

Understanding a Fertilizer Bag

•  Need Ca and Mg –  Irrigation water, dolomite lime, or fertilizer

•  Micros – Supply minimal package unless water

source contains excessive levels

Ca,"Mg,"&"micros"provided?"

Magnesium Deficiency Lower leaf interveinal chlorosis

Brian"W

hipker"

Understanding a Fertilizer Bag

Acidic"or"basic?"

Understanding a Fertilizer Bag Other"Informa&on"

Understanding a Fertilizer Bag

Mixing"and"Target"EC"

200""""""""""""""""""""2.0""""""""13.5""""""17.3"""""""27.0""""""40.5""""""""""""""""1.24"

3/20/13&

4&

Know the critical element concentrations and

interactions? •  Generally N supplied at 100 to 300 ppm •  Ratio of N to K20 usually 1:1 •  Low P is preferred •  Check for Ca, Mg, S, and micros

– Note Cal-Mg formulas use Magnesium Nitrate because of solubility, thus S may not be supplied.

– Epsom salts (Magnesium sulfate) is an excellent source of Mg and S (1#/100 gal water, if water tests confirm the need)

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