5.4 Impacts of Agricultural Practices

Irrigation impacts

Irrigation boosts crop yields but causes major issues: salinization (salt buildup as water evaporates, leaving minerals), waterlogging (roots drown from excess water), and depletion of aquifers via overdrafting. Flood irrigation wastes water through evaporation and runoff, while drip irrigation is far more efficient but costlier to install.

Fertilizers and pesticides

Fertilizers add nitrogen/phosphorus to soil but excess runoff causes eutrophication, algal blooms, and dead zones in waterways. Pesticides kill pests but cause pesticide resistance, biomagnification in food chains (like DDT), and harm to pollinators. Overuse degrades soil health and off-target ecosystems.

Soil degradation & livestock

Monoculture farming depletes soil nutrients and increases pest vulnerability, while heavy tillage causes erosion and loss of topsoil. Concentrated Animal Feeding Operations (CAFOs) produce large waste volumes causing water pollution and greenhouse gases (methane). Overgrazing removes vegetation, leading to erosion and desertification.

Key terms

Salinization

Buildup of salts in soil as irrigation water evaporates, leaving minerals that can harm crops.

Eutrophication

Nutrient enrichment (often from fertilizer runoff) causing algal blooms and oxygen depletion in water bodies.

Biomagnification

Increasing concentration of toxins (like pesticides) at each successive trophic level in a food chain.

CAFOs

Concentrated Animal Feeding Operations; produce large waste volumes causing water pollution and methane emissions.

Monoculture

Growing a single crop species over a large area, depleting soil nutrients and increasing pest vulnerability.

Try an AP-style question

How does tilling (plowing) affect soil?

1. It prevents all erosion
2. It improves soil structure long-term
3. It increases erosion and releases carbon
4. It adds nutrients permanently