The Environmental Science of Sustainable Agriculture
Sustainable agriculture uses methods to produce food that don’t damage the environment or rely on toxic chemicals. Farmers and scientists have developed these methods because they produce food in ways that keep ecosystems and farmland healthy enough to continue to produce food into the future.
Conserving soil with sustainable agriculture
Fertile soil is literally the foundation of farming. Fertile topsoil is vulnerable to erosion, particularly after the crops that grow in them have been harvested. The following methods of working the land help keep soil healthy and reduce the effects of wind and water erosion:
Agroforestry: Agroforestry is the planting of trees and crops together across a field. The trees protect the topsoil by anchoring it in place and blocking winds that could blow it away. And, of course, farmers who use agroforestry can also harvest resources such as firewood or fruit from the trees.
Contour plowing: Soil moves downslope easily with a little help from gravity and water. One way to keep soil in place is to plow in contours that follow the shape of the land. Contour plowing creates crop rows across sloped hillsides rather than up and down the slopes. These rows keep soil from washing downhill.
Intercropping: Intercropping or strip farming is a method of planting two different types of crops in alternate rows in one field. If you harvest the crops at different times of year, then some vegetation is always present to anchor the soil.
Crop rotation: Farmers who use crop rotation plant different crops in their fields each year for a few years in a rotating cycle. This keeps the soil healthy, especially if some years the crops are nitrogen-fixing plants that help replenish nitrogen in the soil. Crop rotation also breaks the reproductive cycle of pest species who often prefer a particular crop.
Terracing: Farms that use terracing create step-like or shelf-like patterns across sloping hills. Each terrace provides a narrow, flat space to plant crops and retains the soil that would otherwise wash downhill.
Reduced tillage: In most cases, the worst soil erosion occurs when fields are tilled, or plowed, to prepare the topsoil for new seeds. Reduced tillage involves plowing tools that prepare the soil without removing all the vegetation or without churning up too much of the soil. Reduced tillage often requires the use of herbicides to help control weeds since some vegetation is left in the fields.
No matter which sustainable agriculture methods farmers use, they also have to add nutrients and organic matter to the soil regularly. In some of these methods, the vegetation left on the fields is a source of organic matter and nutrients.
Farmers can also spread natural fertilizers such as manure, across their fields. For farmers who work with both animals and crops, this is a great way to recycle what would otherwise be a waste product (manure) into something beneficial.
Integrated pest management in sustainable agriculture
In an attempt to reduce the use of pesticides, some farmers practice integrated pest management, or IPM. Instead of using a single method of pest control, IPM combines practices of crop rotation and intercropping with minimal chemical use. The goal of IPM is to reduce the use of chemical pesticides by fostering a habitat that discourages pests.
If an insect or disease infects a monoculture crop (a crop composed of a single species), the entire harvest is in danger of infection. Using crop rotation and intercropping helps reduce this type of damage. Many pests prefer to eat a certain species, and rotating the crop or intercropping interrupts the continuous food supply that a monoculture crop provides.
Another advantage to intercropping is that farmers can plant something that attracts prey insects — insects that will prey on the pests and keep their populations under control naturally.
IPM techniques do rely on chemical pesticides when necessary, but usually only as a last resort. By trying other methods first, the need for chemicals greatly decreases. This decrease in the number of chemicals being used on crops not only keeps pollutants out of the environment but also saves the farmer the cost of continually purchasing stronger pesticide formulas.
The highest cost in IPM comes upfront in training farmers how to manage, care for, and maintain their crop-growing ecosystems.