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Agroecosystems remove nutrients from soils in order to grow crops. This is especially true with the practice of monoculture, which removes large amounts of nutrients from soil. Therefore, in order for more crops to grow, nutrients have to be added back in, which is where fertilizers enter the equation. The main nutrients that are needed by plants to grow, and therefore need to be replaced, are nitrogen and phosphorus, so most fertilizers focus on those two nutrients.
Unfortunately, fertilizers with these nutrients tend to be expensive to produce, and they cause environmental problems through runoff. As croplands are irrigated, or if it rains, the fertilizer in the soil drains away into the local water system. This can cause bodies of water, like the one shown below, to become polluted and dangerous. It can even leak into aquifers to contaminate sources of safe drinking water and cause disease.
IN CONTEXT
The Chesapeake Bay is a prime example of what can happen when fertilizer runoff occurs in high volumes. Phosphorus and nitrogen can cause what is called an algal bloom. Algae love fertilizers, just like crops, and when large amounts of fertilizer drain into bodies of water like the Chesapeake Bay (shown below), huge communities of algae grow. Algal blooms consume much of the oxygen and can threaten fish populations because there is not enough oxygen available.
This phenomenon has also occurred in the Gulf of Mexico, creating an algal bloom as big as some states, where it is difficult for aquatic species to survive.
There are several ways to address the impacts of fertilizers .Some of these are listed in the table below.
| Efforts to Address the Impact of Fertilizers | Effect |
|---|---|
| Organic farming | Organic farming does not use synthetic fertilizer and promotes soil health. |
| Manure | Using natural fertilizers like manure can reduce runoff problems. |
| Changing crops | When farmers change the crops they plant from year to year, it makes different demands on the soil's mix of nutrients, which promotes soil health and usually requires fewer added nutrients. |
Pesticides are chemicals that kill undesirable plants, insects, animals, and fungi that hinder crop production. There are a wide variety of pesticides that lead to an equally wide variety of negative environmental impacts.
The following are four main reasons why pesticides are used:
EXAMPLE
The pesticide DDT was a powerful pesticide that was eventually banned because it harmed many different animal species, especially baby birds.
There are a number of drawbacks to using pesticides.
IN CONTEXT
Atrazine is a prime example of a pesticide with dangerous effects. Atrazine was the most widely used pesticide in the world, yet it was banned in the EU in 2004 when scientists discovered its presence in drinking water and the harmful effects it can have on animals.
The impacts of pesticide can be decreased by using alternatives such as those in the table below.
| Pesticide Alternatives | Effect |
|---|---|
| Insect attractors | Planting crops that attract pests away from the more valuable crop |
| Crop rotation | Rotating crops or planting diverse crops to disrupt insect cycles |
| Integrated pest management | The practice of utilizing natural predators, parasites, and pheromones to disrupt insect cycles |
| Organic farming | Farming techniques that avoid or reduce the use of synthetic pesticides |
| Biological controls | Disruption in the mating of pests by utilizing substances like pheromones |
| GMOs | Planting GMO crops, which have been engineered with pest repellents inside them |
Source: THIS TUTORIAL WAS AUTHORED BY JENSEN MORGAN FOR SOPHIA LEARNING. PLEASE SEE OUR TERMS OF USE.
