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

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

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

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

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

Undesirable effects of chemical control ofpests and weeds

• Upset the balance of ecosystem

• Bioaccumulation

• Reduction of cycling of materials

• Development of new resistant strains

• Unbalanced atmosphere

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

THE ENDThanks for…

Reference book:

Advanced-level Biology for Hong Kong

Website:www.yahoo.com.hk