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 sometimes leak into aquifers, contaminating where we source much of our safe drinking water, and then can cause disease.
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 ways to address the impacts of fertilizers.
|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 also reduce runoff problems.|
|Changing crops||When farmers change what crops they are planting from year to year, it makes different demands on the soil's mix of nutrients, which promotes soil health and usually requires less added nutrients.|
Pesticides are chemicals which kill undesirable plants, insects, animals, and fungi that hinder crop production. There are a wide variety of pesticides with an equally wide variation in negative environmental impacts.
There are four main reasons why pesticides are used:
EXAMPLEThe 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.
The impacts of pesticide can be decreased by using alternatives such as:
|Insect Attractors||Planting crops which attract pests away from the more valuable crop|
|Crop Rotation||Rotating crops or planting a diversity of crops to disrupt insect cycles|
|Integrated Pest Management||The practice of utilizing natural predators, parasites, and pheromones to disrupt insect cycles|
|Organic Farming||Avoids or reduces synthetic pesticides|
|Biological Controls||Disrupts pests from mating by utilizing substances like pheromones|
|GMOs||Planting genetically modified crops, which have been engineered with pest repellent inside them|