Why Is Cotton Harmful to the Soil?

Cotton can be found in everything from T-shirts and cotton swabs to your favorite pair of jeans. But conventional cotton growing practices are under fire for depleting the soil of nutrients. A number of factors, including the heavy use of pesticides, synthetic fertilizers and genetic modification, contribute to the depletion of the soil where cotton crops are planted.

Conventionally grown cotton requires the use of large amounts of chemical pesticides to ensure a healthy crop, which may have a negative impact on the soil and the surrounding environment. In 1995, pesticides were applied to 10 cotton fields in Alabama to combat a severe cotton worm infestation. It rained heavily afterward, and the run-off contaminated Big Nance Creek, killing 240,000 fish over about a 16-mile area. The pesticides used to grow cotton remain in the soil, where they can seep into the groundwater, and require the use of stronger fertilizers.

Growing cotton robs the soil of large amounts of nitrogen and potassium. Even using crop rotation practices, heavy applications of fertilizers are required to maintain healthy plant growth. To grow one pound of raw cotton in the United States, more than one-quarter pound of synthetic fertilizer is needed.

Synthetic nitrogen fertilizers in particular are believed to be the worst for the environment, mostly due to their effect on the water supply. These fertilizers also emit nitrous oxide, which has more of an impact on the ozone layer (and, as a result, global warming) than carbon dioxide.

Genetically modified cotton has been developed to help protect cotton crops from common pests. Some cotton has been genetically modified to include the gene for the Bacillus thuringiensis (Bt) toxin. This modification does protect against some pests and reduces the need for insecticides. However, a study done in India showed that the Bt cotton also does so much damage to soil enzymes and microorganisms, that by the time the cotton is ready to be harvested, the soil in which the cotton was grown is essentially dead.

The issues surrounding conventionally grown cotton do not only affect the soil is which the cotton is grown. Pesticides and synthetic fertilizers that are sprayed on crops can spread through the air to surrounding land; runoff from heavy rain can spread pesticides through the ground, resulting in further soil damage.

Even if cotton farmers practice crop rotation, because the pesticides and fertilizers do not remain on the plants themselves, they can affect future cotton crops, other food crops and land that may not belong to the cotton farmer at all.