Synthetic vs. Organic: What's the Difference?
The main difference between conventional synthetic fertilizers and organic slow-release fertilizers is solubility, or how quickly they dissolve in water.
Synthetic fertilizers dissolve rapidly, releasing nitrogen quickly into the soil. They promote quick "green up" and shallow root systems. They quickly leach into ground or surface waters when it rains, preventing most of the nitrogen from actually being absorbed by your plants. This causes pollution that can lead to algal blooms. Over time, synthetic fertilizers can build up in your soil and kill the microbes that keep your soil and plants healthy.
Slow-release organic fertilizers, along with compost and compost tea, work by providing beneficial microbes and food for microbes already living in your soil. These microbes, in turn, produce nutrients for your plants. These fertilizers are less soluble than synthetics, leading to less leaching of nutrients, and lessening the need for frequent fertilizer applications.
Many landscapers now provide compost tea applications, or you can check out our how-to for brewing your own.