Nitrogen (N) deficiency is the most common and widespread nutrient deficiency in small grains. Plants suffering from N deficiency are pale in comparison to healthy plants due to the breakdown in chlorophyll production.

Specific symptoms of N deficiency first appear (as with phosphorus and potassium) on the oldest leaves with the new leaves remaining relatively green. The older leaves become paler than newer leaves with chlorosis (marked yellowing) beginning at the tip and gradually merging into light green further down the leaf.

As the chlorosis spreads to other leaves, the oldest leaves become totally chlorotic, changing from yellow to almost white in color. However, necrosis (death of leaves or parts thereof) may not set in for some time. N-deficient plants will reach anthesis and maturity before plants with an adequate N supply.

In the field, symptoms almost always start as pale or yellow patches, which may spread rapidly so that, in a fairly short time, the whole field may appear yellowish.