Nitrogen is one of the primary ingredients contained in fertilizers, and the most important ingredient for plant growth. It helps the plant receive energy, make protein, grow, develop and produce seeds. With such an important job, it's understandable why some gardeners would think that the more nitrogen the better. However, in excessive doses, nitrogen alters the plant's ability to grow and produce properly.
Plants that receive too much nitrogen may give off the appearance that they are healthy and thriving by producing lots of new, leafy growth. However, this new growth is often weak, soft and sappy, which makes the plant attractive to various pests and unable to sustain the stress of drought. And if the plant is aromatic, it loses much of its fragrance.
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Although a plant receiving a lot of nitrogen has a plethora of new, leafy foliage, there is often only foliage. It's difficult for fruit and flowers to grow when there is too much nitrogen in the soil. Fruit that does grow is distorted or doesn't ripen properly, while flower buds fall off or are disfigured if they do bloom.
A balanced amount of nitrogen creates a strong, sturdy plant; however, when applied in excess, the reverse happens. Too much nitrogen causes plants to become spindly with frail stems. As the foliage continues to grow abundantly, the weak stems become less able to support the plant. Additionally, root growth is stunted, which leads to even less plant support. Eventually, the plant dies because it can no longer support itself.
When a plant has too much nitrogen, the nitrogen blocks other nutrients from being absorbed by the plant. When a plant can't absorb the proper amounts of necessary nutrients, it alters the sugar and vitamin content in the plant. The result is bitter-tasting fruits and vegetables that are high in nitrogen.
Excessive amounts of nitrogen burn the plant and damage the leaves. Burn is caused by dehydration of the roots and crown that cause the foliage to turn brown or yellow. Nitrogen plant burn doesn't have to occur immediately. Burn symptoms may not show until a few weeks after fertilizing.
- Gardening and Water Quality Protection: Understanding Nitrogen Fertilizers; G. Andrews; 1998
- Food and Fertilizer Technology Center for the Asian and Pacific Region; Excessive Nitrogen Causes Poor Coloring of Tomato; 2003
- National Science Foundation; How Does Your Garden Grow? Some Information on Soil Fertility;
- Vision; Drowning in Excess Nitrogen; Alice Abler; 2010
- University of Minnesota Extension; Responsible Fertilizer Practices for Lawns; Robert J. Mugaas; 2009