Reading deficiency in a leaf
Which element a plant is short of can often be guessed just by looking at its leaves. It is a genuinely useful skill for a grower.
Three questions to the answer
1. Which leaves have changed colour?
Old, mature leaves — think nitrogen or potassium.
Young leaves — think iron.
2. What colour is it?
Yellow (chlorosis) — nitrogen, potassium, sulphur or iron.
Red or purple patches — phosphorus.
Brown — potassium.
3. Which part of the leaf?
Beside the veins — sulphur.
The leaf tip has died — calcium.
The whole leaf evenly yellow — nitrogen.
Field activity
Observe a cultivated plot or a farm and put together a collection of diseased plant parts showing different deficiencies. Identify the mineral that is short in each case.
Collect your specimens without damaging the crop — photograph the leaves rather than picking them where you can.
An important caution
Colour changes in leaves are not caused by mineral deficiency alone. Disease, pests, waterlogging or drought can all produce similar signs. So observe the whole plant before concluding anything.