exceptable ranges for growing lettuce

[Brian]

We are in a Agriculture class in Decatur, Illinois and we have a hydroponic test kit and we have just set up a hydroponic area where we are growing lettuce. We are trying to find out what is the exceptable ranges for growing lettuce. The ranges such as Nitrate Nitrogen range, Phosphorus range, Potassium range, Ammonia Nitrogen range, Sulfate range, Iron range, and Calcium and Magnesium range. This would help us a great deal if we would know these things.