Impact of agriculture Revision Notes

Pesticides and herbicides are chemicals used to control pests and weeds, increasing crop yields. However, excessive or improper use can contaminate soil and water bodies. These chemicals may kill non-target organisms, including beneficial insects, aquatic life, and soil microbes, disrupting ecosystems.

For example, runoff from fields treated with pesticides can enter rivers, harming fish populations. Humans may be exposed through residues on food or contaminated water, potentially causing health issues such as poisoning or long-term chronic effects.

Farmers must balance pest control with environmental safety by applying chemicals at recommended rates and using integrated pest management techniques.

• Excessive pesticide/herbicide use contaminates soil and water.
• Non-target species and beneficial organisms are harmed.
• Human health risks arise from exposure to chemical residues.

Fertilizers supply essential nutrients like nitrogen and phosphorus to crops, boosting growth. Overapplication leads to nutrient runoff into nearby water bodies, causing eutrophication — excessive nutrient enrichment that stimulates algal blooms.

Algal blooms reduce oxygen levels in water when they decompose, killing fish and other aquatic organisms. This process disrupts aquatic ecosystems and can affect human water supplies.

For instance, a farm applying more nitrogen fertilizer than crops can absorb may see nitrate leaching into groundwater, which is hazardous if used for drinking water.

• Excess fertilizers cause nutrient runoff and water pollution.
• Eutrophication leads to oxygen depletion and aquatic life loss.
• Nitrate contamination poses risks to human health.

Irrigation is vital in dry regions but improper management can degrade soil. Salinization occurs when irrigation water evaporates, leaving salts behind that accumulate and inhibit plant growth.

Waterlogging happens when excess irrigation saturates soil, reducing oxygen availability to roots and causing crop stress or death.

For example, continuous flooding of fields without proper drainage can cause waterlogging, while irrigation with saline water or poor drainage leads to salinization over time.

• Salinization results from salt buildup due to evaporation.
• Waterlogging saturates soil, reducing root oxygen and harming crops.
• Both reduce soil fertility and crop yields.

Producing more crops than needed can lead to significant waste, including unsold or spoiled produce. This wastes resources like water, energy, and fertilisers used in production and contributes to environmental degradation through disposal issues.

For example, surplus vegetables discarded due to market oversupply add to landfill waste, releasing greenhouse gases as they decompose.

Efficient production planning and improved storage can reduce waste and environmental impact.

• Overproduction causes food waste and resource inefficiency.
• Waste disposal contributes to pollution and greenhouse gas emissions.
• Better planning and storage reduce waste.

Continuous cropping without replenishing soil nutrients depletes essential mineral ions like nitrogen, phosphorus, and potassium, reducing soil fertility and crop yields over time.

Soil erosion, caused by wind or water removing topsoil, further diminishes productive land and can lead to sedimentation in waterways.

For example, planting the same crop repeatedly without crop rotation or fertilization exhausts soil nutrients. Heavy rains on bare fields can wash away fertile topsoil, degrading land quality.

• Continuous cropping depletes soil mineral nutrients.
• Soil erosion removes fertile topsoil, reducing productivity.
• Both threaten long-term agricultural sustainability.

Farmers may replace staple food crops with cash crops grown for export or profit, such as cotton or coffee. While economically beneficial, this can reduce local food availability and increase dependence on imported food.

This shift may negatively affect local diets and food security, especially in vulnerable communities.

For instance, a region converting rice paddies to grow tobacco may face food shortages if imports are disrupted.

• Cash crops can reduce local food production.
• Food security may be compromised in local communities.
• Economic gains must be balanced with nutritional needs.