Agriculture and the Environment: Impacts and Conservation
Agriculture and the Environment tests the two-way relationship between farming and natural resources: how farming degrades soil, water, vegetation and biodiversity, and the practices that prevent or repair that damage.
Core rules
- Soil erosion follows from bare ground, slope and intense rain or wind. Wind strips the fine fraction from Kalahari sands; sheet erosion removes topsoil and its nutrients first.
- Overgrazing removes palatable grasses, exposes soil and encourages bush encroachment by Acacia species and Dichrostachys, lowering grazing capacity.
- Deforestation for fuel and fields, uncontrolled veld fires and careless cultivation damage vegetation cover and release carbon.
- Water pollution comes from fertiliser, manure runoff, pesticides and eroded sediment; buffer strips along streams and correct application rates reduce it.
- Conservation agriculture: minimum tillage, permanent soil cover and rotation; add water harvesting and integrated pest management to cut chemical dependence.
- Manure and crop residues are resources, not rubbish: compost them and incorporate them.
Worked example: manure nitrogen
Twenty tonnes per hectare of cattle manure containing 1% N supplies 20 000 × 0.01 = 200 kg N/ha. If half becomes available in the first season, that is 100 kg N. Urea at 46% N needs 100 ÷ 0.46 = 217 kg urea to supply the same nitrogen. This shows both the value of manure and why its nutrient content must be tested rather than guessed.
Traps
- Assuming all manure nitrogen is available in year one.
- Burning residues that would protect and feed the soil.
- Blaming drought for damage actually caused by overstocking.
- Ignoring spray drift and unsafe disposal of empty containers.