Compound Fertilisers are products containing 2 or more major nutrients eg. DAP and MAP, which are high in nitrogen and phosphorus.
Straight Fertilisers contain 1 of the macronutrients (NPK); nitrogen, phosphorus and potassium. Single superphosphate and sulphate of ammonia contain other essential nutrients such as sulphur.
Blended Fertilisers have a physical mixture (blend) of the major elements (NPK) with trace elements added when required.