Fertilizing is often referred to as “feeding” plants, but that’s not accurate. Plants feed themselves, producing their own food, sugars, and carbohydrates, through the process of photosynthesis. Plants don’t know or care about the source of needed elements. Chemical (synthetic) fertilizers are manufactured or refined from natural ingredients to make them more concentrated. They are processed into soluble forms that are immediately available to plants. Organic fertilizers are natural materials that have undergone little or no processing. They include both biological (plant and animal) and mineral materials. Here are some key pros and cons for each type:
Chemical (synthetic) fertilizers
- Contain relatively high concentrations of nutrients in a readily available (soluble) form
- Available in a wide variety of concentrations and formulations
- Provide rapid results
- Generally less expensive
- Can be rapidly leached during periods of heavy rain or irrigation
- May contain little or no trace elements
- Require fossil fuels to produce, contributing to climate change
- Released to the plant slowly over a period of months or even years
- Improves soil structure
- Builds populations of beneficial soil organisms
- Adds valuable trace elements
- Nutrients are in low concentrations
- More expensive to buy on a per pound of nutrient basis than synthetic fertilizers.
- May carry OMRI (Organic Materials Review Institute) certification; these are acceptable to use in organic food production.
What chemicals you use in your garden can impact ground water and local watersheds. Excess nitrogen and phosphorus are associated with algal blooms (heavy growth of aquatic plants) and limited oxygen, and cause fish kills in lakes, bays, and nonflowing water bodies.
To reduce fertilizers’ impacts on water quality:
- Apply only materials that are recommended based on results of a soil test.
- Avoid applying excess nitrogen and phosphorus fertilizer.
- Use organic materials or slow-release fertilizers and incorporate into the soil.
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