Central to the science of agronomy is the topic of increasing crop yields and growing healthy plants that provide high nutritional value. While the debate will continue between organic and inorganic fertilizers one fact is clear. When it comes to feeding a hungry world inorganic fertilizers are unsurpassed in their ability to provide high levels of nutrients to plants in an efficient and economical manner. Understanding their differences helps us all to understand their appropriate uses.
Plants fed a strict diet of organic fertilizers are not necessarily healthier to eat than plants fed conventional or manufactured fertilizers. The nutritional quality of food is controlled by the amount and proportional balance of the nutrients fed to the plant, not by the source of the nutrient.
Fertilizers are made of organic or inorganic materials produced from natural or synthetic origins that are added to plant systems in order to supply one or more nutrients required for the plants healthy growth.
Fertilizers produced from organic materials contain carbon and either one or more of the essential plant nutrients nitrogen, phosphorus and potassium.
Animal manures, composts, sewage sludge and by-products from processed animal and vegetable materials are the most common organic fertilizers.
On the other hand carbon is not normally a component in the basic chemical structure of inorganic fertilizers. Usually referred to as manufactured, commercial, synthetic or mineral, inorganic fertilizers are produced from the naturally occurring substances of nitrogen, phosphorus and potassium.
Nitrogen (N), the most used nutrient in plants, comprises about 78% of the atmosphere. To produce nitrogen for fertilizers air is combined with methane from natural gas, and, under pressure and temperature, is converted to anhydrous ammonia which is the basis for most nitrogen fertilizers.
The fossilized remains of marine life deposited in the earth is the primary source of phosphorus (P), the second most used of the primary plant macro-nutrients, N P and K. Its conversion to usable form by the plant mimics natural processes occurring in the soil.
Evaporated oceans are the primary source of the salts from which potassium (K) is produced.
The primary difference between organic and inorganic fertilizers is the nutrient content. Organic fertilizers contain small concentrations of plant nutrients which means they must be applied at high rates in order to provide the nutrient needs of plants.
While it does contain nutrients, manures nutrient levels vary greatly from load to load. Nutrients in manure usually are not readily usable to the plants and are not properly balanced to provide all the nutrient needs the plant requires. Inorganic fertilizers on the other hand can be applied to the exact
levels or nutrients required by the plants.
Transportation costs for manure are relatively high because its nutrient content is relatively low so it is not economical for farm producers to move manure more than a few mile from the feedlot. Large amounts of organic fertilizers must be applied in order to meet the needs of the growing plants. A 50
pound bag of inorganic fertilizer is roughly equivalent to one ton of feedlot manure. In addition, applying excessive manure can create an environmental liability rather than a nutrient source.
Without the use of inorganic fertilizers farmers could not produce enough food to feed the world. The use of fertilizers accounts for an estimated 30-50% of crop yields in the U.S. Higher yields are common in developing areas of the world through the use of inorganic fertilizers. Still, crops use and remove
more nutrients from the soil than we return with fertilizers. It is a necessity to utilize inorganic fertilizers to replace the nutrients taken from the soil during crop growth. The use of inorganic fertilizers produces higher crop yields and higher yields mean more feed available for a hungry world.