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Fertilizers & Plant Food

The Backstory

Synthetic fertilizers and composts may promise rapid results and "time release" formulas, but they are often riddled with cheap fillers like sawdust and harmful chemicals like ammonia and excess nitrogen.

Problems with Conventional Fertilizers

Conventional fertilizers are commonly derived from non-renewable petroleum. In fact, a single 40-pound bag contains the equivalent of 2.5 gallons of gasoline. In addition to their oil base, synthetic fertilizers are spiked with concentrated forms of nitrogen and phosphorus, which are harder for plants to absorb than their naturally occurring counterparts. The excess phosphorus and nitrogen not absorbed by plants runs off into storm drains that feed into rivers and streams, contributing to algae blooms that deprive waterways of oxygen and kill off aquatic life. Such an algal bloom has created a "dead zone" in the Gulf of Mexico the size of New Jersey.

They can also prove detrimental to your lawn in the long run. Healthy soils contain billions of beneficial microorganisms and earthworms that turn thatch and cuttings into nutrients for grass, helping to build a healthy soil. Synthetic fertilizers can kill these helpful organisms, sterilizing your soil.

Problems with Organic Fertilizers

Reassuring as they may sound, organic fertilizers come with their own problems, mainly because they contain nitrogen and phosphorus that can wash off into waterways, just as conventional fertilizers do. And just like conventional fertilizers fortified with synthetic ammonia, manure and guano (bird droppings) both have high levels of naturally occurring ammonia that can "burn" plants.

Organic fertilizers may also contain ingredients that have not been harvested in the most eco-friendly way. Bone, blood and feather meals are byproducts of the meat industries and are added to fertilizers as a source of nutrients. Despite the health benefits to your soil, these byproducts have the potential to contaminate it with disease-causing pathogens, and they may have come from unsanitary factory farms. Fish meal, another industry byproduct, may be contaminated with PCBs and mercury and could come from overharvested fish populations. To give some sense of the human health threats these animal byproducts can pose, the Northeast Organic Farming Association, a USDA-accredited organic certifying agency, allows their use only under the strict warning that humans should avoid direct contact with them.

Peat is another additive in many fertilizers, but its use could actually contribute to global warming. Peat bogs store more carbon dioxide than all of the world's tropical rainforests, and when the peat is harvested, all the stored CO2 is released back into the atmosphere. These wetland areas also support diverse ecosystems that can be damaged when the bogs are drained to harvest peat. Often the drained land is converted into forests, but the wildlife diversity is lost. In some areas, butterfly populations that thrived in wetland peat bogs have decreased as much as 90 percent.

Finally, some organic fertilizers contain sewage sludge, leftover from wastewater treatment plants. Considered a useful soil additive for its high concentration of nitrogen and phosphorus, sewage sludge also comes with all the pharmaceuticals, antibacterials, industrial synthetic chemicals, heavy metals and other chemicals that wastewater treatment plants aren't able to remove. Though the EPA has endorsed sewage sludge, or biosolids, as fertilizers for years, recent findings have brought their safety into question. A February 2008 Environmental Science and Technology study revealed that earthworms living in soil treated with sludge were absorbing the pharmaceuticals and personal care product ingredients that treatment plants leave behind. While the study wasn't conclusive, their presence in earthworms led scientists to suspect chemicals were building up in the crops growing in the soil and also in birds and animals that ate the worms.