Nutrient Deficiencies

Healthy plant

Plants deprived of one or more essential nutrients show poor growth, and where deficiencies are severe, may exhibit characteristic symptoms.

The sweet corn plant shown here has been grown in sand and supplied with adequate quantities of all nutrients in solution. Compare this with plants grown with nutrient solutions from which N, P, K, or S has been omitted.

Sulfur deficiency

The importance of sulfur (S) as a plant nutrient in Australian soils has often not been realized because sulfur has been added when phosphorus (P) deficiencies are corrected with single superphosphate. In plants, sulfur is a component of several amino acids and is therefore found in proteins.

Sulfur deficiency causes leaf chlorosis and may be confused with nitrogen (N) deficiency. However, unlike nitrogen, sulfur cannot be remobilized in the plant, so chlorosis is first seen on the younger leaves where nutrient demands are highest.

Potassium deficiency

Australian soils often have relatively high levels of soluble or exchangeable potassium, and deficiencies are less frequent than for nitrogen (N) or phosphorus (P). Within the plant, potassium (K) remains as a soluble ion. One of its roles is in regulating the uptake and transpiration of water, which helps maintain the turgor or rigidity of plant cells.

Potassium-deficient plants are more susceptible to disease and show less drought tolerance. Scorching of leaf margins may be seen. Weakening of stalks in grasses may lead to lodging (plants falling over).

Nitrogen deficiency

Most soil nitrogen (N) is present as organic compounds that are unavailable to plants. Mineralization reactions release plant-available N. Look at the Soil Organic Matter module. Look at the Soil Organic Matter module.

Nitrogen is a constituent of proteins, DNA, chlorophyll, and many other molecules present in plants.

Deficiency symptoms are first seen as chlorosis or yellowing of the older leaves because nitrogen from proteins is mobilized and translocated to the newer, growing leaves. Plants are stunted, and the older leaves may die.

Phosphorus deficiency

Plants have a high requirement for phosphorus (P), but the amount present in the soil solution and available for immediate uptake is generally very low. For this reason, P deficiencies are common, especially in Australian soils. In plants, P is a component of the energy transfer compounds ATP and ADP, as well as DNA.

Symptoms of P deficiency include marked reduction in growth, and in some grass species like corn, leaves may show purple discoloration. Chlorosis of leaves is not seen.