What are inorganic fertilizers,
and what do they do to soil?
Plants need an adequate supply of nutrients to sustain themselves. Most farmers today use chemical fertilizers as a source of nutrients because continuous cropping depletes soil of nutrients. Nitrogen, a product of an industrial procedure called the Haber Process, and phosphorus, a nutrient obtained from mines, are used often. Chemical fertilizers are effective, but these fertilizers lack the organic mater that supports beneficial organisms in soil. These organisms are needed to maintain healthy soil and enhance plant nutrition.
When most of the humus is gone and the fertilizers continue to be applied to the crops, more nutrients may leach into nearby waterways, often causing algae blooms. This process is called "eutrophication." When fertilizer runoff enters a body of water, aquatic plant growth increases, and floating algae beds often form. These beds block sunlight and cause bottom dwelling plants to die. Bacteria then eat these decaying plants, reducing the water's oxygen content, which kills a number of fish and other aquatic organisms. This problem is worsened by the release of hydrogen sulfide and methane, compounds lethal to most fish, from organisms that flourish in oxygen-depleted environments.
Some alternatives to chemical fertilizers are organic fertilizers like animal or human waste, plant waste, and rotating crops with plants that naturally add nitrogen to the soil. These steps toward sustainability prevent soil loss and degradation as well as keeping nutrients in the soil.
Realizing the need for better nutrient application methods and standards, Pennsylvania has been involved in nutrient management since the early 1980s, when nutrients were identified as a problem in the Chesapeake Bay. In 1997, a nutrient management law was implemented in PA that requires an N-based nutrient management plan on farms with more than two animal units per acre. Fertilizers are to be applied only as needed, and farmers are encouraged to monitor their own soil.
Pennsylvanian farmers are welcome to seek membership in the Nutrient Management Program, and those with an approved NM plan implement it in accordance with the approved schedule. Approved NM plans specifically detail the application of nutrients for each field or crop group and any necessary "best management practices" to address nutrient runoff or leaching concerns.
To read more about nutrient management, please visit the following sites: