HortSense Stewardship gardening links outside WSU Fertilizers supplement the nutrients already in the soil.
Organics require warm soil to break down and release their nutrients.
Too much of any fertilizer can cause pollution by leaching into groundwater or running off into surface waters. Organics may be safer in this respect because they tend to release their nutrients more slowly. Some common organic fertilizers are listed below. Their approximate percentages of nitrogen, phosphorus, and potassium are listed in parentheses. These percentages can vary somewhat from product to product.