Topic 3: Questions and Answers

• Answer the questions below.
• Give yourself one hour.
• Check your answers afterwards and do corrections.

Questions

1. Describe the pressure a growing population places on natural resources. (5)
2. Outline three agricultural practices that can contribute to the sustainable utilisation of natural resources in agriculture. (6)
3. Describe the three types of soil degradation. (6)
4. Name five warning signs that soil erosion is taking place. (5)
5. Define water quality. (6)
6. What is meant by water source? (1)
7. Describe the water cycle. (10)
8. Describe five methods that farmers can use to increase the amount of water that enters the soil. (10)
9. What is agricultural pollution? (4)
10. List the five major soil pollutants. (5)
11. Describe the three factors that determine the severity of a pollutant. (6)
12. What is silage and how does it contribute to pollution? (6)

[Total marks 70]

Answers 

1.                      
   • Land: A small part of the Earth’s surface can be used for agriculture. Only 12% of South Arica’s land is suitable for agriculture. The increasing demand for food resulted in traditional farming methods being replaced with use of chemicals and fertilisers. These practices are non-sustainable as they lead to soil degradation.
   • Water: Only about 0,036% of the total amount of water on the planet is found in surface water sources such as rivers, lakes and dams.
   • SA’s annual population growth rate is between 2% and 2,5%. This means that nearly a million more people per year need food, using the same amount of soil and water.
2.                    
   • Conserve the soil: so that rain does not wash it into rivers or dams, it is not blown by wind, and not polluted by chemicals (including fertiliser, herbicides and pesticides).
   • Conserve water: check tanks for leaks, ensure it is not polluted by chemicals or animal waste.
   • Manage animal waste on the farm: use it to enrich the soil.
   • Plan farm processes (e.g. ploughing and irrigation): to avoid negative impact on the environment and natural resources.
3.                      
   • Physical degradation: when the structure of the soil is damaged by wrong cultivation methods or ploughing when the soil is too wet or too dry.
   • Biological degradation is caused by cuttings from unregistered nurseries, or illegally imported plants and seeds, spread of pests or pathogens, and by tilling and converting areas with natural vegetation to agricultural land.
   • Chemical degradation is caused by the use of chemicals.
4.                  
   • Muddy water in streams and rivers
   • Dams filled with mud
   • Plants with bare roots
   • Dust storms
   • New soil deposits: water carries soil from higher ground to lower ground
   • Pedestals
   • Bare ground
   • Deep cattle and footpaths. (Any 5)
5. Water quality is the physical, chemical, biological and aesthetic characteristics or properties of water, which determine its fitness for use and its ability to maintain the health of aquatic ecosystems.
6. It is where the available water is stored (surface or underground).
7. The water in rivers, etc. is in the liquid phase. Through evaporation, this water changes to the gas phase. Ice changes to water vapour through sublimation. Evaporation and sublimation use heat energy from the sun. The water vapour rises up into the atmosphere and cools down. When the vapour cools down, tiny drops of water form (condensation). The tiny droplets combine with one another to form clouds. When these droplets become heavy enough, they fall to the ground in the form of rain, snow, or hail (precipitation). Plants absorb water through their roots. The water moves up through the plant and evaporates from the leaves. The water in the air rises and forms clouds. The clouds produce rain and the cycle begins again.
8. Method 1: stop soil erosion.
   Method 2: pocketing water – make shallow pockets in the soil.
   Method 3: end-of-season ploughing – at the end of the rainy season the soil is still moist; when the next rainy season starts, the soil is loose.
   Method 4: no-tillage farming – crop remains form mulch; prevents evaporation and soil doesn’t become compacted.
   Method 5: preserving the plant cover to decrease water runoff and prevent soil compaction.
9. Agricultural pollution is the pollution of water, soil or air by agricultural activities.
10. Fertiliser; herbicides and pesticides; wrong irrigation practices; improper soil management; spillages.
11. The severity of a pollutant is determined by its:
    • chemical nature – whether it is a salt, heavy metal, acid, etc.
    • Its concentration – the higher the concentration, the more harmful it is.
    • Its persistence – the longer it takes to break down, the more harmful it is.
12. Silage is fodder made from grass crops (e.g. maize, sorghum or alfalfa). The plant material is first allowed to ferment and stored for use when grazing is scarce. The process of making silage is called silaging or ensiling. During fermentation a liquid is formed, which contains nitric acid, which can pollute water sources and cause eutrophication.

[Total marks: 70]