IB Environmental systems and societies 5.2D Soil Conservation Notes

Soil Conservation: Protecting the Thin Layer That Feeds Us

1. Soil conservation refers to all strategies used to protect, maintain, or improve soil quality, ensuring long-term agricultural productivity and ecosystem health.
2. These techniques address erosion control, fertility maintenance, and sustainable cultivation, bringing environmental, economic, and sociocultural benefits.
3. Soil conservation matters because degraded soil causes serious problems.
   1. Loss of topsoil
   2. Declining fertility
   3. Erosion, desertification, and compaction
   4. Reduced agricultural yields
   5. Lower ecosystem resilience

Conservation from Water Erosion

1. Terracing
   1. Terracing reshapes steep slopes into flat platforms that slow water moving downslope.
   2. Water spreads across each terrace, lowering erosion risk and increasing infiltration.
   3. It reduces soil loss on steep land, allows cultivation of otherwise unusable areas, and prevents gully formation.
2. Contour Ploughing
   1. Ploughing follows the natural contour lines of the land rather than running up and down slopes.
   2. The furrows slow runoff and give water time to soak into the soil.
   3. It reduces topsoil removal and the formation of rills and small gullies.
3. Bunding
   1. Bunds are low retaining walls built along field boundaries.
   2. They capture rainfall, sediment, and runoff, storing water for irrigation.
   3. They cut the loss of soil and nutrients and are most useful where rainfall is intense and seasonal.
4. Drainage Systems
   1. Drains, ditches, and settling ponds manage excess water and let sediment settle before water leaves the field.
   2. They prevent waterlogging and stagnant water while reducing erosion and nutrient loss.
5. Cover Crops
   1. Plants are grown on bare soil between main crop seasons so their roots bind the soil and intercept rainfall.
   2. They reduce water erosion, improve soil structure, and add organic matter when ploughed under.

Conservation from Wind Erosion

1. Windbreaks
   1. Rows of trees or hedges are planted along field edges and within farms.
   2. The vegetation slows the wind so it can no longer lift topsoil.
   3. Windbreaks protect topsoil, shield crops from wind damage, and increase biodiversity around farmland.
2. Cover Crops
   1. Keeping the soil covered stops loose particles from blowing away.
   2. The vegetation protects soil from drying out and reduces its exposure to strong winds.
   3. Cover crops reduce wind erosion, add organic matter, and support healthy soil microorganisms.

Conserving Fertility with Soil Conditioners

1. Lime
   1. Lime contains calcium carbonate, which neutralises acidic soils.
   2. Raising soil pH most directly improves phosphorus availability and reduces toxic aluminium and manganese.
   3. Lime promotes healthy microbial communities, improving soil biological activity.
2. Organic Matter: Compost, Manure, and Green Manure
   1. Organic matter improves soil texture, structure, aeration, and drainage, making soils more resilient.
   2. Nutrients are released slowly, reducing leaching and building long-term fertility.
   3. Compost and manure enrich soil organic carbon, improving water retention and microbial health.
   4. Green manure is a crop grown specifically to plough back into the soil, adding organic material and nutrients.

Sustainable Cultivation Techniques

1. Avoid marginal land so steep or poor soils are not degraded.
2. Prevent overgrazing and overcropping to maintain soil structure and fertility.
3. Strip cropping alternates crops in strips to reduce erosion and improve fertility.
4. Mixed cropping and crop rotation diversify nutrients and reduce pest buildup.
5. Reduced tillage minimises soil disturbance, preserving structure and reducing erosion.
6. Limit heavy machinery to prevent soil compaction and degradation.

Benefits of Soil Conservation

Environmental Benefits

1. Biodiversity: healthy soil supports diverse ecosystems.
2. Water quality: less erosion means less sediment and nutrient runoff into water bodies.
3. Carbon sequestration: soil rich in organic matter stores carbon, helping to mitigate climate change.

Sociocultural Benefits

1. Food security: healthy soil supports reliable food production.
2. Cultural practices: techniques like terracing preserve traditional farming methods.
3. Community resilience: sustainable practices reduce vulnerability to climate change and economic shocks.