Deficiencies in trace elements - mainly iron - are known as chlorosis.  Specific symptoms are identified with the name.  For example, iron chlorosis is a condition due to lack of iron.  Iron chlorosis causes a leaf to become yellow.  The newest leaves on the ends of branches are the most affected by this condition, although in severe cases all the plant's leaves are affected.  In advanced stages, iron chlorosis causes plant tissue to die, manifested as brown scorched areas of the leaf.  There are three ways to treat iron chlorosis problems with iron-providing fertiliser containing, for example, iron sulphate: foliar sprays, soil incorporation or trunk injection.  A simple approach is to apply a mixture of iron sulphate and sulphur to the soil.

Copperas, commonly known as iron vitriol or green vitriol, is a form of ferrous sulphate heptahydrate.  This green salt has a physical property like wet snow.  It is difficult to store but very easy to dissolve.  In the past a main source of copperas was extraction from iron pyrite-rich nodules.  Nowadays, there are two main sources:

• finishing of steel
• production of titanium dioxide via the sulphate process.