Phosphorus deficiency

During the early stages of vegetative development, the most noticeable feature of phosphorus (P) deficiency in wheat is the reduced growth and vigor of the plant. The color of all leaves of P-deficient plants becomes a dark dull green with slight mottling of the oldest leaf. Leaves appear coiled to a greater degree than normal; old leaves sometimes encase younger leaves. New growth can appear spindly and may remain folded for some time.

Specific symptoms are, however, on the old leaves. Chlorosis begins at the tip of the old leaf and moves down the front of the leaf. The base of the leaf, like the remainder of the plant, stays dark green. Unlike nitrogen (N) deficiency, necrosis of these chlorotic areas is fairly rapid, with the tip becoming orange to dark brown and shrivelling and the remainder turning yellow. When this occurs, the second oldest leaf has generally taken on the early symptoms of P deficiency. Severe deficiency often causes pale to yellowish red leaves, starting with the lower leaves and moving from the leaf tips inward. Affected tissue may turn brown and, with severe deficiency, may eventually die. Green portions of the leaves may be bluish-green and the base of the culms purple. Other common symptoms of P deficiency are delayed and irregular plant maturity and small heads.

P deficiency is usually more general across a field than N deficiency and usually results in stunted plants with fewer shoots if the deficiency is mild. The whole field is affected to a greater or lesser degree unless the deficiency is due to faulty fertilizer or lime application.

Phosphorus Deficiency