AP Environmental Science Unit 5 Notes: Agriculture & Food Production

Green Revolution

Mid-20th-century “package” of agricultural technologies and practices (HYVs, synthetic fertilizers, irrigation, pesticides, mechanization) that greatly increased crop yields, with environmental and social trade-offs.

High-yield varieties (HYVs)

Crop varieties (especially wheat and rice) bred to produce more grain per plant under ideal conditions, typically requiring reliable water, high nutrients, and pest/weed control to reach full yield.

Synthetic fertilizers

Industrial fertilizers that supply key nutrients (nitrogen, phosphorus, potassium) to boost plant growth, but can contribute to nutrient pollution when overapplied or washed off fields.

Irrigation

Artificial application of water to soil to support crop growth; can stabilize yields but may increase water withdrawals and contribute to soil problems like salinization or waterlogging.

Pesticides

Chemicals designed to kill pests that reduce crop yield/quality; can cause non-target effects, runoff/drift, and select for resistant pest populations.

Mechanization (in agriculture)

Use of machinery (e.g., tractors, harvesters) and industrial inputs to increase farm efficiency and output; often increases fossil-fuel energy use.

Eutrophication

Nutrient enrichment of water (often from fertilizer/manure runoff) that triggers algal blooms; decomposition then lowers dissolved oxygen, potentially creating “dead zones” and causing fish kills.

Pesticide resistance

Evolutionary increase in the proportion of pests that survive a pesticide due to natural selection (resistant individuals survive and reproduce), reducing pesticide effectiveness over time.

Soil salinization

Buildup of salts in soil—often linked to irrigation in dry regions when water evaporates and leaves salts behind—reducing plant growth and potentially making fields unproductive.

Monoculture

Planting large areas with a single crop; can reduce biodiversity and increase vulnerability to pests and disease outbreaks.

Conventional tillage

Frequent plowing that breaks soil structure and leaves soil bare, often increasing topsoil erosion by wind and water.

No-till farming

Farming method that minimizes soil disturbance and leaves crop residues on the field, reducing erosion; may increase reliance on herbicides for weed control.

Cover crops

Plants grown mainly to protect/enrich soil (rather than harvest); reduce erosion, add organic matter, and can reduce nutrient loss from fields.

Contour plowing

Plowing along the natural contours of a slope to slow runoff, reduce water speed, and decrease soil erosion.

Terracing

Building step-like levels on steep slopes to slow runoff and reduce erosion by decreasing the slope length and water flow energy.

Leaching

Downward movement of dissolved substances (notably nitrate) through soil with infiltrating water, often contaminating groundwater.

Runoff

Surface flow of water over land that can carry sediment, nutrients (especially phosphate attached to soil), and chemicals into streams and lakes.

Aquifer depletion

Decline of groundwater levels when pumping exceeds natural recharge, raising pumping costs and sometimes contributing to land subsidence.

Water withdrawals (agriculture)

Removal of water from rivers, lakes, or aquifers for irrigation and other uses; large withdrawals can reduce river flow and lower groundwater levels.

Drip irrigation

Irrigation method that delivers water directly to the base/root zone of plants through tubing and emitters; typically the most water-efficient but higher cost and requires maintenance (clogging risk).

Center-pivot irrigation

Mechanized sprinkler system that rotates around a central point; offers controlled application but can lose water to evaporation/wind drift and requires energy for pumping/pressurizing.

Integrated Pest Management (IPM)

Pest-control strategy combining monitoring, thresholds, prevention (e.g., rotation), and targeted controls, using chemical pesticides as a last resort to minimize environmental impacts while maintaining yields.

Pesticide treadmill

Cycle where pesticide use selects for resistant pests, leading to increased or stronger pesticide applications over time to maintain control.

Biological control

Use of natural enemies (predators, parasites, pathogens) to suppress pest populations; can reduce pesticide use but may create unintended ecological impacts if introduced species become invasive or affect non-target organisms.

Concentrated Animal Feeding Operation (CAFO)

Industrial livestock facility where many animals are confined and fed grain-based diets; produces large amounts of concentrated manure, creating risks of nutrient runoff, water contamination, and air-quality issues.