Most plants, especially those that are grown outside of their native ranges, need soil supplements in the form of fertilizer. This might include adding nitrogen for growth, phosphorous for bloom production or potassium for resistance to drought and cold. However, fertilizers must be applied carefully to ensure there are no harmful results.
Application Rates
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Fertilizer application rates can vary with the type of fertilizer that is needed to produce the desired results. For example, nitrogen, which is added to increase leaf and stem production, can kill plants quickly if applied at a higher level than recommended. Nitrogen works best if applied often and in small amounts. On the other hand, phosphorous can stay in the soil for years and is applied occasionally in larger amounts.
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Monitoring Fertilizer Levels in Soil
Because excess fertilizer can kill plants and damage the soil where plants grow, fertilizer levels must be carefully monitored to be sure the correct amount is always present. This is accomplished with a soil test done by a soil lab or with a hand held device. Most county agricultural extension offices can help you with soil testing.
Expense of Fertilizer
No matter what kind of fertilizer you use, few people can manufacture it on their own. Even making organic fertilizer by making compost takes time and space and does not provide an immediate solution to a nutrient deficiency in the lawn or garden. For that reason, fertilizer must be purchased and frequent applications can be expensive over time.
Toxicity of Fertilizers
Even organic fertilizers can be toxic if consumed in large amounts. Chemical fertilizers carry warning labels and many are toxic to humans and pets if consumed or if there is prolonged contact with skin.
Potential Runoff to Non-Target Areas
Both chemical and organic fertilizers have the potential to cause environmental damage by running off into non-target areas during heavy rain. For example, nitrogen and phosphorous in chemical fertilizers and bacteria in organic fertilizer can cause excess algae growth in waterways and harm the quality of drinking water.