Nutrient Deficiency

Guide to Nutrient Deficiency Symptoms

If this topic fascinates you I highly recommend these links
This first link is particularly good about describing interactions and in depth pathology. Read this when you have time to absorb and comprehend the information presented. 
Plant Physiology - Chapter 5 -Mineral Nutrition 
 Blue Planet has done a good job of presenting photos for identification, and present quick reference to nutrient interactions. 
Blue Planet Nutrients 


The best site I know of for pictures of nutrient deficiencies is
http://customers.hbci.com/~wenonah/min-def/list.htm

Calcium deficiency - Blossom end rot

How to make a water soluble calcium

Phosphorous deficiency

Potassium deficiency

Sulfur deficiency

From http://www.hydroponics.net/learn/deficiency_by_element.asp

From: http://www.breedbay.co.uk/gallery/data/500/Soil_PH_chart.jpg

From: http://www.organicfertilizer.in/micronutrients.htm

From http://www.hydroponics-at-home.com/plant-nutrient-deficiency.html

From http://www.hydroponics-at-home.com/hydroponics-information.html

Hollow stem in broccoli is related to boron deficiency.

 Nutrient Antagonism and Interaction

GrowOrganic Peaceful Valley has a good http://youtu.be/CLFbwByeb9k

I found this conversation interesting.  Alan from BioNutrient.Org talks about soil building and how soil health effects our health.
Alan Chartockin Conversation with Dan Kittredge