Sustainable agriculture Revision Notes

Organic fertilizers are natural materials added to soil to improve fertility and structure without synthetic chemicals. Examples include crop residues (leftover stalks and leaves after harvest) and animal manure. These materials decompose, releasing nutrients slowly and enhancing soil organic matter, which improves water retention and aeration.

Using organic fertilizers reduces reliance on chemical fertilisers that can cause pollution and soil degradation. For example, a farm applying composted manure can maintain crop yields while supporting beneficial soil microbes and preventing nutrient runoff into waterways.

• Crop residues and manure enrich soil naturally.
• Slow nutrient release supports long-term fertility.
• Improves soil structure and water retention.
• Reduces chemical fertiliser use and pollution risk.

Managed grazing involves controlling livestock movement to prevent overgrazing, which can lead to soil compaction, loss of vegetation cover, and erosion. Rotational grazing is a common method where animals are moved between paddocks to allow vegetation recovery.

For instance, a cattle farmer divides pasture into sections and rotates herds every few days. This maintains plant diversity and root systems, stabilising soil and reducing erosion risk.

This technique balances livestock production with land conservation, ensuring pasture remains productive over time.

• Rotational grazing prevents overgrazing and soil damage.
• Allows vegetation recovery and root regrowth.
• Maintains pasture productivity and biodiversity.
• Reduces soil compaction and erosion risk.

Crop rotation is the practice of growing different crops sequentially on the same land to maintain soil nutrients and disrupt pest and disease cycles. For example, rotating legumes (which fix nitrogen) with cereals replenishes soil nitrogen naturally.

Planting pest-resistant and drought-resistant crop varieties reduces the need for chemical pesticides and excessive irrigation. For example, drought-tolerant maize varieties can survive dry spells, reducing water demand.

Together, these practices improve yield stability and reduce environmental impacts from chemicals and water overuse.

• Crop rotation maintains soil nutrient balance.
• Breaks pest and disease cycles naturally.
• Pest-resistant crops reduce pesticide use.
• Drought-resistant crops lower irrigation needs.
• Supports sustainable yield and environmental protection.

Trickle drip irrigation delivers water directly to plant roots in small, controlled amounts, minimising evaporation and runoff. This method is highly efficient compared to flood or sprinkler irrigation.

Rainwater harvesting collects and stores rainfall from roofs or land surfaces for later agricultural use, reducing dependence on groundwater or rivers.

For example, a vegetable farm using drip irrigation combined with rainwater tanks can maintain crops during dry periods while conserving water resources, crucial in water-scarce regions.

• Drip irrigation targets water efficiently to roots.
• Reduces water loss by evaporation and runoff.
• Rainwater harvesting stores natural rainfall for irrigation.
• Decreases reliance on external water sources.
• Enhances water use efficiency in farming.

Unsustainable agricultural practices, such as continuous monoculture, overgrazing, and excessive tillage, can cause soil erosion, nutrient depletion, and loss of soil structure. For example, clearing vegetation on steep slopes for farming without protection leads to heavy topsoil loss during rains.

Soil erosion reduces land productivity and causes sedimentation in rivers, harming aquatic ecosystems.

Soil conservation strategies include contour ploughing (ploughing along slope contours to reduce runoff), terracing (creating stepped fields on slopes), maintaining ground cover with cover crops, and applying mulches to protect soil surface. These methods reduce erosion and maintain soil fertility over time.

• Unsustainable farming causes soil erosion and nutrient loss.
• Soil erosion lowers productivity and pollutes waterways.
• Contour ploughing and terracing reduce runoff on slopes.
• Cover crops and mulches protect soil surface.
• Conservation maintains long-term land productivity.