Background Agricultural Connections
Modern agriculture methods play an important role in our society. Agricultural producers utilize the latest research in crop genetics and land management as well as animal production methods to produce a safe and abundant food supply. In addition, agricultural plants and animals provide fuel, clothing, shelter and thousands of other products we use every day. This lesson challenges students to explore the role of synthetic fertilizers, modern agricultural machinery, and soil and water conservation techniques.
Most agricultural fertilizers contain nitrogen, phosphorous, and potassium, which are commonly limiting nutrients for plants. Fertilizers vary in the concentration of these nutrients; farmers choose which formulation to use based on the soil content of their fields and what they are growing. Fertilizers provide for more vigorous plant growth, which can improve crop yields and help prevent soil erosion. Modern plowing and tilling implements, pulled by tractors, allow farmers to prepare large fields for planting by turning over soil and providing an even seed bed.
These farming methods can have environmental impacts. Land that is tilled and left bare (for example, over the winter) is more susceptible to erosion by wind or water. Topsoil that is washed or blown away can take decades to naturally replace. Excess nutrients applied to the soil can reach waterways through runoff and the groundwater. Nutrient input from agricultural land in the Midwest is thought to contribute to the dead zone in the Gulf of Mexico. In Activity 1 of this lesson, students design an experiment to test the effect of fertilizer on algae growth. In Activity 2, students see a demonstration of water erosion in bare soil.
Farmers are land stewards who can reduce and reverse the impact of agriculture on the environment by using farming practices that conserve resources. In Activity 3, students research the following conservation practices:
- Crop Rotation: The practice of growing different types of crops on the same plot of land in sequential growing seasons. Different crops use different amounts of nutrients. If the same crop is planted continuously, the soil will become depleted of some nutrients more than others, increasing fertilizer use. For example, some crops use a lot of nitrogen, while others are able to return nitrogen to the soil. A common rotation is to plant corn one year and soybeans the next year, since soybeans are legumes, which return nitrogen to the soil.
- Cover Cropping: Cover cropping helps reduce erosion. Instead of leaving bare soil when the main crop is harvested, farmers plant an additional crop and leave it in the field over the winter. For example, a farmer might harvest corn and then plant rye to cover the field.
- Conservation Tillage: Soil preparation that leaves crop residue from the previous year’s crop on the field. For example, corn stalks may be left on the field after harvest and soybeans planted directly into the corn residue the next spring. Keeping the soil covered in this manner reduces erosion and runoff
- Habitat Preservation: An area of a farm that is reserved in or returned to its pre-cultivation state, such as a grassland or wetland. These areas provide food and shelter for wildlife and prevent erosion and runoff, and provide an alternative to farming marginal land.
- Contour Farming: In hilly areas, rows of crops are planted perpendicular to the slope rather than parallel to the slope, following the contour of the land. This slows runoff from the land, allowing water to infiltrate the soil and reducing erosion.
- Buffer Stripping: An area of vegetation, often grass, planted at the edge of a field next to a body of water such as a lake or river. Filter strips help protect water quality by trapping and filtering sediment, nutrients, and other pollutants in runoff.
Most farmers employ several of these methods, and many farmers are innovating and doing on-farm research to make the best sustainable choices for their land.
