Despite land degradation, agricultural yields continue to increase, in part thanks to synthetic fertilizers and pesticides that temporarily boost soil productivity. Fertilizer consumption has increased exponentially since the 1950s, so much so that 50% of all commercial fertilizer ever produced has been applied since 1984.
While fertilizer application can increase short term crop yields or keep the grass on your lawn green through November, it comes with its share of detrimental environmental and health effects. Many of the problems stem from the inability of the soil to retain all of the fertilizer applied. In fact, it is estimated that about one half of every metric ton of fertilizer applied to fields never even makes it into plant tissue, but instead ends up evaporating or being washed into local waterways.
Nitrogen (N), phosphorus (P), and potassium (K) are the primary major nutrients required for plant growth and are the main components of most fertilizers. These chemicals are energy intensive to produce, create vast amounts of waste, and contribute to greenhouse gas emissions. Producing one unit of N requires 1.4 units of carbon and 3 units of carbon are required to manufacture, transport and apply 1 unit of P as P2O5 fertilizer. For every ton of phosphoric acid produced, five tons of phosphogypsum are generated. Over the past 50 years, more than 700 million metric tons of phosphogypsum have accumulated in Florida alone, huge stacks at times covering more than 300 hectares at more than 60 meters high with settling ponds that threaten local water sources. The production of nitric acid, the primary feedstock for synthetic commercial fertilizer, is also a source of nitrous oxide, a greenhouse gas 310 times more potent than carbon dioxide, and accounted for 15.9 Tg CO2E in 2005, the equivalent emissions of 2.9 million vehicles.
According to the World Health Organization, some 3 million people a year suffer from severe pesticide poisoning. Pesticide exposure can lead to cancer, birth defects and damage to the nervous system. Drinking water contaminated by pesticide runoff is a main source of exposure.
Excess fertilizer use and runoff causes eutrophication in waterways which threatens animal and plant health. The surplus nutrients stimulate excessive plant growth, such as algal blooms, which consume nearly all the available oxygen in the water and cause other plants and animals to suffocate. Surplus nitrogen and phosphorus from fertilizer runoff, animal manure, soil erosion and sewage have created a “dead zone” of more than 7000 square miles in the Gulf of Mexico near the mouth of the Mississippi River. These huge algal blooms are starving out shellfish and threatening commercial fisheries and area economies-the U.N. reported nearly 150 dead zones throughout the world’s oceans in 2007.
Solutions: Reduced fertilizer use
In response to the negative environmental effects of fertilizer and pesticide consumption, several countries and U.S. states have enacted taxes upon or banned the use of these chemicals. Learn more
The nitrogen concentration in compost is found in stable compounds in the organic matter. The nitrogen compounds remain in the soil, available for uptake by the plant roots over a long period of time, greatly reducing the threat of water pollution and eutrophication. According to the European Commission, long-term application of compost will establish higher nitrogen levels in soils such that compost will completely displace synthetic fertilizers.
Data quantifying the amount of reduced pesticide and fertilizer use attributable to compost use is not readily available across a wide range of applications. Subsequently, models that calculate the climate benefits of improved organics management through composting, such as the EPA’s WAste Reduction Model (WARM), fail to account for the upstream benefits of reduced chemical fertilizer and pesticide consumption. According to the EPA, “To the extent that compost may replace or reduce the need for these substances, composting may result in reduced energy-related GHG emissions.”
In a study commissioned by Seattle Public Utilities, Morris and Bagby (2007) concluded that residents using natural lawn care practices compared to synthetic practices produced an annual community benefit of $75 in ongoing public health, ecological, water conservation and hazardous waste management benefits. Natural lawn care practices produced “between $16 and $21 of environmental benefits from reduced use of synthetic fertilizers and pesticides, $8 of environmental benefits for switching from gas to electricity for lawn mowing, $42 in cost savings due to reduced irrigation, and $5 or $6 from lower hazardous waste management costs. There also is a potential one time avoidance of $31 in construction costs resulting from reduced need for storm water detention and diversion capacity.”