Organic materials and fertilizers improve the soil texture, allowing it to hold water longer, and increase the bacterial and fungal activity in the soil. So, they not only assist your plants, they help the soil. Synthetic fertilizers, on the other hand, deplete the soil of its nutrients, making it unproductive

Organic fertilizers such as manures, compost or bone meal are derived directly from plant or animal sources, according to Ross Penhallegon, horticulturist with the Oregon State University Extension Service. Inorganic fertilizers such as ammonium sulfate or ammonium phosphate are often called commercial or synthetic fertilizers because they go through a manufacturing process, although many of them come from naturally occurring mineral deposits.

Organic fertilizers usually contain plant nutrients in low concentrations. Many of these nutrients have to be converted into inorganic forms by soil bacteria and fungi before plants can use them, so they typically are more slowly released, especially during cold weather when soil microbes are not as active.