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Fertilizer burn is a condition that emerges in plants that have been over fertilized. The excess fertilizer in the soil acts to actively pull water out of the plant, causing it to dryout and interfering with plant growth. The burn is visible as an area of browning, yellowing, and withering. If it is allowed to persist, the plant can actually die, especially if it is at a vulnerable stage of development.
The mechanism behind fertilizer burn is fairly simple. When plants are fertilized normally, they absorb salts and minerals from the fertilizer, maintaining a high osmotic pressure in addition to providing nutrients. Since water flows from areas of low to high pressure, the high osmotic pressure in the plant helps pull water up into it so that it can meet its water needs.
When too much fertilizer is applied, it creates a high osmotic pressure in the soil solution that surrounds the roots of the plant. This interferes with the ability of the plant to absorb water and can sometimes pull water out of the plant. Roots and leaves alike can be damaged, causing a plant to become unhealthy. Fertilizer burn can also happen when fertilizer levels are relatively normal, but the plant is not getting enough water.
Sometimes, the burn appears almost immediately after excessive fertilization although in other instances, it may take several weeks for signs of damage to appear. This is especially common with organic and time release fertilizer products, in which time is required for salts to start building up to a dangerous level. Treatment involves removing the excess fertilizer, if possible, and flushing the soil with water to remove the buildup of salts.
People can avoid fertilizer burn by making sure that the needs of their plants are met without exceeding them. Any fertilizer product is capable of causing burn, no matter what the label says, and it should be applied in moderation and in accordance with a strict schedule to avoid using too much. In addition to being damaging to the plants, over fertilization can also be harmful for the environment, as it generates runoff that can pollute waterways. Nutrient pollution leads to a proliferation of algae and other organisms in the water, which can interfere with water quality and hurt fish populations; in waterways that drain to the ocean, it can cause problems with sea life as well.