Lack of Nitrogen Causes What in Gardening?

Plants use significant amounts of nitrogen for growth.

Plants require the proper balance of nutrients to thrive. When nitrogen becomes deficient, garden plants display various deficiency symptoms. Recognizing and understanding the results of inadequate nitrogen in your garden plants enables you to correct the nutrient imbalance and enjoy a healthy, visually appealing garden.

Yellowing

Nitrogen deficiency usually begins with yellowing in older leaves, which are often found at the base of plants. Leaf veins become slightly lighter in color than the surrounding tissue. Generally, the rest of the plant remains green until the deficiency becomes more advanced, at which point the entire plant yellows and eventually dies if not given nitrogen fertilizer.

Slow, Weak Growth

Nitrogen-deficient plants experience fragile, unusually slow growth. Leaves, stems and new shoots are long and lanky and break easily. Foliage appears abnormally small and fails to grow and thrive. Trees experience stunting and reduced canopies, along with undersized twig growth and dieback.

Poor Fruiting and Flowering

Plants lacking nitrogen bloom poorly and produce limited, if non-existent, crops. Fruit quality is also affected. In oranges, the peel is pale in color and the flavor is compromised. Those plants lacking nitrogen that do flower or fruit may shed leaves, so they can use the limited available nitrogen for fruiting and flowering.

Susceptibility to Pests and Disease

When plants are strong and adequately nourished, they fight off various fungal diseases and pests like scale insects. Plants weakened by nitrogen deficiency are prone to attack, and their weakened state prevents them from resisting such invaders.

Nitrogen-Deficiency Causes

Nitrogen deficiency in the soil occurs for a variety of reasons. Nitrogen leaches from the soil during overwatering or heavy rainfall. Nutrients may also become unavailable to plants if the soil is excessively dry or waterlogged. Correcting watering practices may initiate nitrogen uptake. Nitrogen deficiency also occurs in soils low in organic matter or those that contain under-decomposed materials such as sawdust, straw, grass clippings and wood chips. Always use well-composted soil amendments.

Warning

Lack of nitrogen isn't the only cause of yellowing foliage and poor plant growth. A variety of other nutrient deficiencies cause pale leaves and stunting, including insufficient iron, potassium, sulfur, magnesium and zinc. When unsure about nitrogen deficiency, take a soil test. Some plants also tend to yellow according to the seasons, so familiarize yourself with what your plants look like throughout the year. Many pests and diseases cause symptoms such as yellowing leaves and defoliation. Inspect foliage carefully for problems before fertilizing -- and always follow fertilizer directions carefully, because too much fertilizer is toxic to plants.

References

• University of Arizona Cooperative Extension; Guide to Symptoms of Plant Nutrient Deficiencies; Shanyn Hosier, et al.; May 1999
• Cornell University Cooperative Extension; Recognizing Nutrient Deficiency Symptoms; James W. Boodley; June 2003
• University of Nevada Cooperative Extension; Recognizing Plant Nutrient Deficiencies; Angela O'Callaghan, Ph.D.
• Michigan State University Extension; Are You Sure That Yellowing Means Nitrogen Deficiency? Emily Sneller; May 13, 2011
• University of Florida IFAS Extension; Macronutrient Deficiencies in Citrus -- Nitrogen, Phosphorus and Potassium; Mongi Zekri, et al; 2009

Resources

• University of Florida; Nitrogen Deficiency in Palms;Timothy K. Broschat; 2009