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

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% P₂0₅   
8% K₂0   
24% total nutrient content   

   
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) 

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

  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

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