1. Yes, and it gets complicated trying to explain the differences between Nitrates and Nitrites. In a good, healthy soil the Soil Food Web, the soil microbes, change the various types of Nitrogen into what they plants can use and in many instances the plants are "fed" that N by some types of fungi. Some forms of Nitrogen are more readily available than others, more soluble, and are therefore more susceptible to leaching from the soil and polluting your groundwater.
2. Whether the N in an animal manure is more soluble or not depends on the form it is in. Poultry manure and horse manure have very readily available forms of N and so are "hot" while cattle, sheep, and goat manures are more stable and are considered "cold". All animal manures should be composted before being put in the garden, fresh manure should not be put on a garden plot, especially if food is being grown there.
3. Poultry and horse manures have very readily available forms of N and that availability is what makes them "hot".

Very informative- Thank you for the response.
I assume that your comment, "All animal manures should be composted before being put in the garden, fresh manure should not be put on a garden plot, especially if food is being grown there." is to guard against pathogens, is that correct?
That brings up another thought in light of the recent Tomato and Jalapeno problems- How is e-coli found when checking vegetable crops?

Manure contains a lot of nutrients in the form of salts which are readily available. Salts dissolve rapidly in water and go into solution where they are available to plants. Salts in high concentrations will burn plants which is why fresh manure is considered 'hot.' Nutrients in plants are part of an organic complex. For example nitrogen is a component of protein. The organic materials break down at different rates depending on how resistant they are to microbial decay and therefore release nutrients at different rates. The actual nutrients used by plants are the same and are in the same form regardless of whether they come from a chemical (salt) fertilizer or an organic source such as manure or compost.

Composting animal manures is to guard against the potential disease pathogens that are present in all manures. The disease pathogens found on the vegetables were found after smears were taken from those vegetables adn cultured in the labs, after people started getting really ill after eating those foods. Anytime someone gets ill after eating some food that should be reported to your county health department and if someone is hospitilized that will be done, once it is determined the problem was food poisoning.

So would I be correct to assume that it's basically impossible for the average person to know whether or not their veg is infected with e-coli?