人教版高中英语必修4 Unit 2 Working the land Using language 阅读课2课件（15张ppt）

(共15张PPT)
Chemical or
Organic Farming
What is the substance we put on the soil which makes crops grow ?
It is fertilizer.
How many kinds of fertilizers do farmers use ?
There are two kinds. They are chemical fertilizers and natural ones.
safe food
green food
≈ organic food
safe or not ?
A quiz:
Organic food just refers to vegetables and fruits.
Green food has a color of green.
Green food is certain to be healthy and safe.
Organic food is free of chemical fertilizers.
Organic food is grown away from dirty water supply.
Green food can be grown around big paper factories.
×
×
×
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Fasting reading
Why are chemical fertilizers so popular in farming today?
3. What is organic farming?
2. Long-term use of chemical fertilizers is
good. (T/F)
Organic farming is simply farming without using chemicals.
Long-term use of chemical fertilizers can cause damage to the land, even more dangerous, to
people’s health.
Because chemical fertilizers can help stop crop disease and increase production.
Careful reading
1. What problems are caused by using chemical fertilizers?

2.What is the advantage of organic farming?

3. What’s the main idea of paragraph4?
1.What problems are caused by using chemical fertilizers?
First, they damage the land by ___________________________________________
Chemicals ________________________________
for a long time. And this affects _____and _____
__________ ,since they __________ the crops and cannot be _________ ; these chemicals in the food supply ________ in the bodies, _________ cancers or other diseases. In addition, fruit and other food with chemicals grow too fast to _____________________ having more ______ than ________________________

killing the helpful bacteria and pests as well as the harmful ones.
stay in the ground and underground water
crops
and humans
animals
get inside
washed off
build up
leading to
be full of much nutrition
water
vitamins and minerals
2.What is the advantage of organic farming?
Make the soil richer in minerals and so
more fertile.
2) Reduce diseases in crops and help them
grow strong and healthy.
3) Keep the air, soil, water and crops free from chemicals.
1. Farmers often change the kind of crop in each field every few years.
corn ,wheat
peas soybeans
Put the minerals back into the soil, making it rich and healthy.
3. What’s the main idea of paragraph 4?
There are many organic farming methods for
making the land healthy and fertile.
Methods Advantages

2. Farmers plant crops with different lengths of roots.
This uses different levels of soil.
crops that need a deeper level of soil (vegetables)
crops that use the surface of the soil (peanuts)
Methods Advantages

3. planting grass between crops
prevent wind or water from carrying away the soil and leave it in the ground to become a natural fertilizer for the next year’s crop
Methods Advantages

Summary
chemical fertilizers
stop crop disease
increase production
cause problems
damage the land
lead to illnesses
not nutritious
natural fertilizers
pollute the environment...
reduce disease
makes soil fertile
protect the environment
strong and healthy crops
organic farming
A summary of organic farming:
no use of chemical fertilizers
away from industrial areas
away from dirty water supply
no air pollution
some special ways of farming to use
healthy and safe food
Language points
1. bacteria 单数:bacterium 细菌
2. pest 害虫，害鸟 3. turn to 转向,求助于,翻到
4. build up 逐渐积聚;增进,增强;逐步建立
Build up one’s strength after an illness.
5. lead to 导致; 通向;往
His mistakes led to his failure.
This road leads to the railway station.
6. focus on 聚集；集中
Please focus your mind on the reason.
All eyes were focused on him.
7. keep…free from“远离”或“避免”
keep free from emotional reactions keep free from restrictions