Fertilizing Lawns: Consider the Source
Most synthetic lawn fertilizers contain at least 40 percent slow-release nitrogen. Slow-release nitrogen becomes available to the plant over a period of time depending on the soil moisture, temperature and microbial activity. The balance of the nitrogen is water soluble nitrogen, which is readily available for plant uptake.
In addition to supplying nitrogen over a longer period of time, slow-release nitrogen sources have a lower risk of burning plants and a lower potential to pollute water than water-soluble nitrogen sources. The tradeoff is that slow-release nitrogen is usually more expensive.
Natural organic fertilizers supply nitrogen in complex organic forms that not immediately available to plants. They require warm, moist soils for microbial activity to release nitrogen. Natural organic fertilizers are well-suited for applications during warm summer months when the potential for burning plants with high-salt synthetic fertilizers is high.
Lawns grown on mostly sandy soils should rely more on slow-release nitrogen to reduce the possibility of nitrogen leaching out of the root zone. Research shows that on most soils with some silt and clay, nitrogen leaching from lawns is rare.
