page 74

ESSENTIAL ELEMENTS, MOBILITY AND pH EFFECT

essential element - an element required by plants for normal growth, development and completion 
                               of its life cycle, and which cannot be substituted for by other chemical 
                               compounds.  

17 ELEMENTS ARE REQUIRED BY PLANTS   
 3 supplied naturally by air and water - comprise the bulk of the plant   
    C, H, 0     
 6 macronutrients - required at 0.1 to 6% of the dry weight of plants   
    N, P, K, S, Ca, Mg    
 8 micronutrients - required at 1 to 300 ppm of the dry weight of plants   
    Fe, Zn, Cu, Mo, B, Mn, Cl, Ni    
    Cl and Ni are ubiquitous - hence, will not be addressed in detail   

The essential elements can be easily remembered by a catch phrase such as   
C. HOPKiNS CaFe, CuB, Mn, C.l. MoNiZnsky, Mgr   
  

NUTRIENT MOBILITY  
Two directions of movement in plants   
1) acropetal - means towards the apex; transport up the in xylem   
2) basipetal - means towards the base; transport down in the phloem   

Two classifications of nutrient mobility   
1) mobile - moves both up and down the plant by both acropetal and basipetal  transport (in both  
                  the xylem and the phloem).   
    Deficiency appears on older leaves first.   
    N, P, K, Mg, S     
2) immobile -  moves up the plant by only acropetal (in the xylem) transport   
    Deficiency appears on new leaves first.   
    Ca, Fe, Zn, Mo, B, Cu, Mn   
  

EFFECT OF pH    
The pH determines solubility in the soil  
1) more available at low pH (below 5.5), and less available at high pH.    
    Fe, Zn, Cu, Mn, B    
2) more available at high pH (above 6.5), and less available at low pH.   
    N, K, Mg, Ca, S, Mo     
3) more available at intermediate pH (6-7)     
    P      

Ideal pH  
slightly acid:   
a) around 6.5 for field soil   
b) around 5.5-6.0 for artificial growing media made with peat moss or composted bark


page 75

FERTILIZER ANALYSIS AND RATIO

FERTILIZER ANALYSIS  
analysis - sequence of 3 numbers on the fertilizer label that gives the percent composition of  
                N-P205-K20 in a fertilizer; required by law to be on the label of every fertilizer sold.   

Example: 8-8-8 means the fertilizer contains:   
8% N   
8% P20  
8% K20   
24% total nutrient content   

    Buy fertilizers by price per pound of fertilizer, not price per bag.   

100 lb. of 8-8-8 @ $4.99
100 lb. @ 24% = 24 lb. of nutrients
@ $4.99 =
20.8 cents per lb

100 lb. of 13-13-13 @ $5.99
100 lb @ 39% = 39 lb. of nutrients
@ $5.99 =
15.3 cents per lb.

   
FERTILIZER RATIO   
ratio - the relative proportion of N to P205 to K20 in a fertilizer.

Analysis
8-8-8
20-20-20
10-20-10
18-6-12

Ratio
1-1-1
1-1-1
1-2-1
3-1-2

    
USING FERTILIZER RATIOS TO MANIPULATE GROWTH   
a) to favor vegetative growth    

  • use a high N, low P and K fertilizer 
  • for example, use a 2-1-1 or 3-1-1 ratio fertilizer (higher 1st number) 

b) to favor flowering, root and underground storage organ growth   

  • use a low N, high P and/or K fertilizer 
  • for example, use a 1-2-2 or 1-3-2 ratio fertilizer (higher 2nd and/or 3rd number) 

page 76

FUNCTION OF NUTRIENTS
Nutrient  Symbol Function
nitrogen

N
1) Component of chlorophyll; amino acids, proteins and enzymes;  
    nucleic acids (RNA and DNA); some auxins and cytokinins. 
phosphorus

P
1) Component of the high energy compounds ATP, NADPH and   
    NADP; nucleic acids (DNA and RNA); and phospholipids. 
potassium

K
1) Needed for protein and enzyme synthesis and activation.    
2) Involved in maintaining proper water balance    
3) Needed for photosynthesis. 
magnesium

Mg
1) Component of chlorophyll.    
2) Activates many enzymes. 
calcium

Ca
1) Ca pectates in middle lamella of cell wall cement cells together.    
2) Required for normal cell division and meristem growth.    
3) Stabilizes membranes
sulfur

S
1) Component of several amino acids (methionine, cystine,
cysteine).
iron

Fe
1) Required for chlorophyll synthesis.    
2) Component of many enzymes and carriers, especially those of   
    electron transport chain.
zinc

Zn
1) Required for tryptophan, hence auxin (IAA), synthesis.
manganese

Mn
1) Required for chlorophyll synthesis.    
2) Activates many enzymes.
copper

Cu
1) Required for chlorophyll synthesis.    
2) Component of many enzymes and carriers, especially those of   
    electron transport chain.
boron

B
1) Required for complete flowering and fruit development.    
2) Involved in translocation of carbohydrates and hormones. 
molybdenum

Mo
1) Component of enzymes in N metabolism (nitrate to organic N)    
2) Component of enzymes in nitrogen fixation (N gas to ammonia)
chlorine

Cl
1) Oxygen evolution in photosynthesis    
2) Stomatal functioning 
nickel

Ni
1) Component of several enzymes, especially urease (breaks
down urea)
 

page 77

TISSUE CONCENTRATION, DEFICIENCY SYMPTOMS AND FERTILIZER SOURCES

Nutrient

Tissue Concentration

Characteristic Deficiency Symptom*
Fertilizer Sources

  
MACRONUTRIENTS

N

2-6%
older leaves - overall chlorosis NH4 nitrate, sulfate, phosphate;     
K, Na, or Ca nitrate; urea 

P

0.2-1.2%
older leaves - deep green, purple coloration of petioles superphosphate; NH4 or K phosphate; phosphoric acid 

K

1-6%
(luxury
consumption)
older leaves - interveinal chlorosis with marginal and tip necrosis K nitrate, chloride, phosphate, or sulfate; K frit 

Mg

 0.2-1%
older leaves - interveinal chlorosis and bronze coloration dolomite (Ca/Mg carbonate),   
Mg sulfate (Epsom salt)

Ca

0.5-2% 
stem tips - die, small leaves limes (Ca carbonate/hydroxide);     
Ca sulfate (gypsum) or nitrate;   
superphosphate

S

0.3-0.7%
all leaves overall chlorosis, on young leaves 1st then progresses to old leaves sulfate carriers; elemental S;   
air pollution; superphosphate

  
MICRONUTRIENTS** 

Fe

50-300 ppm
young leaves - severe interveinal chlorosis  Fe chelate; Fe sulfate; some pesticides 

Zn

5-75 ppm
new growth - rosetted growth & small leaves Zn chelate; Zn sulfate;     
some pesticides

Mn

30-300 ppm
young leaves - interveinal chlorosis with necrosis when severe Mn chelate; Mn sulfate;   
some pesticides

Cu

5-30 ppm
stem tips - die, stunted; leaves small; multiple buds formed Cu chelate; Cu sulfate;   
some pesticides

B

30-200 ppm
stem tips - internodes short, thick; leaves thick, brittle, with necrosis borax; boric acid

Mo

1 ppm
similar to N deficiency, except occurs on young leaves. Na or NH4 molybdate 

Cl & Ni

?
virtually never seen in nature ubiquitous

*chlorosis = yellowing;  necrosis = browning;  interveinal = between the veins  
**micronutrients are often applied as a multi-micronutrient mix; ex. STEM, PERK, Micromax


page 78

NUTRIENTS WITH SIMILAR DEFICIENCY SYMPTOMS
 

Nutrients That Cause Interveinal Chlorosis

Deficiency Of

 Interveinal Chlorosis Occurs On

 With No Necrosis

 Plus Necrosis

Young Leaves

Fe

Mn

Old Leaves

Mg

K
 

Nutrients That Cause Overall Chlorosis

Overall Chlorosis Occurs on

Deficiency Of

Old Leaves

N

New Leaves

Mo

New Leaves, Then Spreading to Old Leaves

S
 

Nutrients That Effect the Shoot Tip

Various Deficiency Symptoms
on Growing Point, Emerging Leaves or
Shoot Tip 

Deficiency Of

Small New Leaves and Rosetted New Growth

Zn

Thick and Brittle New Leaves

B

New Leaves Distorted and Necrotic

Ca

Vague Symptoms: New Leaves Small, Wilted, Translucent or Necrotic

Cu
 

page 79

NITROGEN CYCLE

  WAYS IN WHICH NITROGEN IS LOST FROM THE SOIL   
1) leaching (especially nitrate which is negatively charged)   
2) plant absorption   
3) microorganisms consume (see C:N ratio next page)   
4) denitrification


page 80

NITROGEN CONVERSIONS

NITROGEN REACTIONS  
mineralization or ammonification -the conversion of organic nitrogen (in the -NH2 form) to  
                                                       inorganic nitrogen (in the NH4 form).  
                                                     - the speed of conversion depends on the C:N ratio (see below).  
nitrification - a two step process converting ammonium to nitrite, then nitrite to nitrate.   
                   - the soil bacterium Nitrosomonas converts ammonium to nitrite  
                   - the soil bacterium Nitrobacter converts nitrite to nitrate  
                   - this occurs very quickly so little ammonium (which can be toxic if high) and  
                     virtually no nitrite (which is highly toxic) accumulates in the soil.  
denitrification - the conversion of nitrate in the soil to gaseous nitrogen that escapes into the  
                         atmosphere.   

nitrogen fixation - the conversion of gaseous nitrogen to ammonia.   
                           - only nitrogen fixing microorganisms can cause nitrogen fixation;   
                             some form symbiotic relationships with plants (see table below)  
  

CARBON:NITROGEN (C:N) RATIOS IN ORGANIC MATTER  
C:N Ratio - proportion  of carbon to nitrogen present in organic matter.   
a) high C:N ratio - wood, sawdust, uncomposted bark   
    - microbes use up all nitrogen in organic matter when consuming carbon,  
    - then the microbes use up the nitrogen in the soil   
b) low C:N ratio - manure, bone meal, fish emulsion, organic fertilizers   
    - microbes consume carbon,   
    - then release excess nitrogen from the organic matter into the soil  
    - thus, low C:N organic matter acts as an organic nitrogen fertilizer 
   
 

MICROORGANISMS THAT CAN FIX NITROGEN  
Type Microorganism

Nitrogen-Fixing
Microorganism

Forms Symbiotic
Relationship With
1) Bacteria 

Rhizobium

Legumes
(soybean, clover, mesquite)
2) Bacteria

Azotobacter 
Clostridium

free living only
3) Filamentous Bacteria

some Actinomycetes

Some woody plants,
(Alnus and Elaeagnus)

4)
Blue-green algae

 

Anabaena

Azolla and Cycads
(can also be free living)
 

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