Inorganic fertilizer contains a combination of chemicals and minerals that were produced in a refinery, and it offers gardeners and farmers a more reliable form of plant nourishment because its nutrient levels are calculated to be consistent. However, inorganic fertilizer also affects soil in ways that can harm plants if the fertilizer is not applied carefully.
According to the Maryland Cooperative Extension, inorganic fertilizers provide the same three major nutrients that organic fertilizers do: nitrogen, phosphorus and potassium. Plants receive these nutrients more quickly from inorganic fertilizer, however, because the refinery has already broken them down into a digestible form; organic fertilizers must dissolve in the soil first, and the amount of nutrition they deliver is imprecise. For these reasons, inorganic fertilizer has a swifter, more efficient effect on plants.
The immediate availability of nutrients in inorganic fertilizer results in these nutrients, particularly nitrogen, being "loose" -- this means that rain and other sources of water can easily wash the nutrients below the root level of the plants and eventually into the surrounding streams, rivers and lakes. As a result, the plants receive no nourishment and must receive more fertilizer, and high concentrations of nitrogen and other compounds enter the ecosystem, with potentially fatal results for plant and animal life.
Unlike organic fertilizer, inorganic fertilizer must be applied carefully or the plants may die. This is because high levels of the chemical salts in inorganic fertilizer may "burn" a plant's root system -- although the process is called "burning," the effect is actually dehydration, which occurs when the salts draw out all the moisture from the roots and desiccate them.