5.4 Impacts of Agricultural Practices

TLDR

Some farming methods cause real environmental damage, and three you need to know are tilling, slash-and-burn farming, and the use of fertilizers. Each one boosts food production in the short term but creates problems like soil erosion, lost nutrients, and water pollution. On the AP Environmental Science exam, you should be able to describe these practices and explain the specific environmental harm each one causes.

Impacts of Agricultural Practices Summary

Agricultural practices can increase food production while also damaging soil, air, and water systems. For AP Environmental Science, the required examples are tilling, slash-and-burn farming, and fertilizer use.

The exam usually wants a cause-and-effect chain. Tilling exposes soil and increases erosion, slash-and-burn releases carbon dioxide and reduces long-term soil fertility, and fertilizer runoff adds excess nutrients to water, which can trigger eutrophication.

The damage from tilling, slash-and-burn, and fertilizers sets up Sustainable Agriculture (5.15) and Integrated Pest Management (5.14) later in Unit 5. Free-response prompts often ask you to pair a harmful practice with a solution, so knowing the problem first gives you something concrete to fix.

Three Farming Practices and Their Environmental Damage

• The three agricultural practices to know for this topic are tilling, slash-and-burn farming, and the use of fertilizers.
• Tilling loosens soil but leaves it exposed, which speeds up soil erosion and washes away nutrient-rich topsoil.
• Slash-and-burn clears land with fire, releasing carbon dioxide and pushing farmers to clear more land as soil loses fertility.
• Fertilizers add nutrients to soil, but runoff carries those nutrients into water and can trigger eutrophication.
• For each practice, practice naming the action and then explaining the specific environmental harm it causes.

Agricultural Practices That Cause Environmental Damage

Agricultural practices are the techniques farmers use to grow more food on their land. Some are more efficient than others, and some cause more environmental damage. For this topic, focus on three: tilling, slash-and-burn farming, and the use of fertilizers.

Tilling

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Tilling, also called plowing, digs up and turns over clumps of soil. This loosens the soil so water, air, and nutrients can move through it more easily, which can help crops grow.

The downside is erosion. Once soil is broken up and exposed, it becomes easy for wind and water to carry it away. The nutrient-rich topsoil is usually the first to go, often ending up in nearby streams, rivers, or the ocean. Tilling also disturbs the microbes living in the soil. Over time, repeated tilling leaves farmland less fertile.

Slash-and-Burn Farming

Slash-and-burn farming clears land by cutting down vegetation and then burning it. The ash adds some nutrients back to the soil, creating ready-to-use farmland in the short term.

The problem is that the soil loses fertility fairly quickly, which pushes farmers to slash and burn new areas of land to keep growing crops. Burning vegetation also releases carbon dioxide into the atmosphere, which connects this practice to climate change.

Fertilizers

Fertilizers are chemical or organic substances added to soil to boost fertility and help crops grow. Used correctly, they raise crop yields. Used in excess, they can damage the crops they are meant to support.

The bigger environmental issue is runoff. Fertilizers add extra nutrients like nitrogen and phosphorus to the soil, and rain washes those nutrients into nearby bodies of water. That nutrient buildup can trigger eutrophication, where algae grow rapidly, then die off and get broken down by bacteria that use up the oxygen in the water. Low oxygen levels can cause die-offs of fish and other aquatic species, and the pollution can also affect water supplies.

Naming a Farming Practice and Explaining Its Harm

MCQ: Multiple-choice questions often give you a scenario and ask which practice caused it, or what consequence a practice leads to. Match the practice to its main effect: tilling to soil erosion, slash-and-burn to lost soil fertility and carbon dioxide release, and fertilizers to runoff and eutrophication.

Free Response: Free-response questions usually want a two-part answer: describe the practice, then explain the environmental harm. A weak answer just names the practice. A strong answer explains the chain of cause and effect.

For fertilizers, do not stop at "runoff." Walk through it: extra nutrients wash into water, algae grow rapidly, algae die and decompose, bacteria use up oxygen, and fish and other organisms die from low oxygen. That full chain is what earns points.

Common Trap: When a prompt asks for a harmful agricultural practice, stick to practices that genuinely cause damage. Stay on topic by pairing each practice with a specific, accurate consequence instead of a vague statement like "it hurts the environment."

Common Misconceptions

• Misconception: Tilling is purely harmful.
  Actually: Tilling is not purely harmful. It does help crops by loosening soil for water and air, but it also exposes soil to erosion. A good answer mentions both sides when the question asks for benefits and drawbacks.
• Misconception: Algae directly poison the water during eutrophication.
  Actually: Eutrophication does not mean algae directly poison the water. The damage comes from algae dying, decomposing, and using up oxygen, which then causes aquatic organisms to die off.
• Misconception: Slash-and-burn is a permanent solution.
  Actually: Slash-and-burn is not a permanent solution. The cleared soil loses fertility quickly, which forces farmers to clear even more land.
• Misconception: Fertilizer is always helpful in larger amounts.
  Actually: Fertilizer is not always helpful in larger amounts. Too much fertilizer can damage crops and makes runoff pollution worse.
• Misconception: Fertilizer includes only synthetic types.
  Actually: "Fertilizer" includes both synthetic and organic types. Even organic fertilizers like manure can cause runoff and eutrophication if overused.

Related AP Environmental Science Guides

• 5.1 The Tragedy of the Commons
• 5.2 Clearcutting
• 5.0 Required Environmental Legislation
• 5.5 Irrigation Methods
• 5.3 The Green Revolution
• 5.6 Pest Control Methods