2. What is it? - Production of food through the growing of plants (Cultivation) Why do we need it? - Population growth leads to high demand for food - 10% of the lands on the Earth’s surface are suitable for agricultural practices

3. Misuse of agricultural lands and inappropriate agricultural practices result in the destroy of farmlands and various effects on the environment 1. Inappropriate agricultural practices a. Monoculture b. Excessive use of chemical fertilizers c. Over-harvesting d. Inappropriate irrigation techniques 2. Undesirable effects of chemical control of pests and weeds

4. Monoculture - Growing the same type of crops over several seasons on the same field - Ecological effects: 1. Inappropriate agricultural practices Depletion of particular kind of minerals in soil  Infertile soil Spread of a particular pest  accumulation of pesticide Reduce biodiversity in an area

5. Excessive use of chemical fertilizers - Chemical fertilizers provide extra inorganic nutrients, mainly nitrogen, potassium, etc. - Environmental problems : Soil destruction Water pollution and algal bloom Air pollution Soil destruction Algal bloom

6. Over-harvesting Plant tissues and minerals are taken away Nutrients depleted from the soil Infertile soil Inappropriate irrigation techniques Salinization caused by irrigation water Leach salts deep into the soil Abandoned farmland

7. Undesirable effects of chemical control of pests and weeds Upset the balance of ecosystem Bioaccumulation Reduction of cycling of materials Development of new resistant strains Unbalanced atmosphere

8. Crop rotation system Cultivate different kinds of crops on the same piece of land in turn One kind of crops should be leguminous plants Balancing the use of chemical fertilizers and organic fertilizers Organic fertilizers include animal manure and plant waste

9. THE END Thanks for… Reference book: Advanced-level Biology for Hong Kong Website: www.yahoo.com.hk