Differences between organic and non-organic food?

Spread across my desk are seed packets from lettuce and salad leaf seeds sown yesterday as part of my usual successional sowing:

Lettuce - Colour shades mixed (T&M), Little Gem (T&M), Lobjoits Green Cos (Kings Seeds) and Mazur (free trial from DT Brown)

Salad Leaves - Green Spray Mibuna (Sea Spring Seeds - a lovely local seed company here in Dorset), Nice n Spicey Mixed (T&M), Speedy Mix (T&M), Wild Herby Leaf mix (also local - Pennard Plants).

When we eat them fresh from the garden it will be in the knowledge that nothing has been applied to the soil or the plants that will be harmful to either or to us. 

Can that be said of all foods, I doubt it and recently published research reports significant differences between organically and conventionally produced food.

Well worth a read:

Clear differences between organic and non-organic food, study finds

See also further discussion:

Will eating organic food make you healthier?