Human Influences on the Environment

Human Influences on the Environment

​Factor Controlled	How it is controlled​	Reason​
​Soil Ions	​adding fertilizers	​minerals for proteins and growth
Soil structure​	ploughing field, adding manure, aeration​ of heavy, clay soils	Oxygen for active transport/mineral, water uptake ​
Soil pH​	​adding lime to acidic soils	low pH reduces mineral uptake​
Carbon dioxide, light and heat​	burning fuels in glasshouses​/greenhouses/poly tunnels	​limiting factors of photosynthesis

​Improving yields from crop plants

​Some ways of optimizing crop yields:

Multiple Choice

Which of these conditions can be controlled in a glasshouse?

• temperature

• carbon dioxide concentration

• light

• all of these

WHAT is fertilizer?

​Fertilizer is food for plants. It adds to the nutrients found naturally in the soil. Like people, plants require nutrients to grow.

Plants need 17 nutrients to grow normally.

Nitrogen (N), phosphorus (P), potassium (K) and sulfur (S) are nutrients needed in large amounts.

These are called macro-nutrients. Crops also need certain nutrients in much smaller amounts. These are called micro-nutrients. Soil contains nutrients but not necessarily in the right amounts for good plant growth. As crops grow, they use nutrients from the soil. When they are harvested, they take nutrients with them. Although some nutrients remain in the soil and are left in the crop residues that remain on a field after a crop is harvested, soil nutrients need to be replenished for the next crop. This can be done through many methods, but the most effective way is by adding fertilizer.

A better understanding of how fertilizers work and how to use them most effectively enables farmers to apply soil nutrients in the amounts they need, and when and where they are needed, minimizing or avoiding loss of nutrients to soil, water and air.

Both conventional fertilizer and organic nutrients must be applied correctly. If too much is used, there is a risk that nutrients will run off the fields into waterways and/or be released into the air. Too many nutrients in water can cause excessive algae and plant growth that reduces oxygen levels in water and harms aquatic life.

ARE FERTILIZERS HARMFUL TO THE ENVIRONMENT?

Prepared in industries.

Best suited for crop requirements.

Can easily dissolve in water hence washes away.

More chances of overuse.

Does not contribute to soil texture.

Expensive

Commercial/Inorganic Fertilizers

Contain little or no synthetic materials. Animal manure or crop residues.

Some nutrients are water soluble that can be washed away.

Most nutrients released slowly as microbes decompose them.

Relatively less amount of nutrients than commercial fertilizers.

Might not have the right proportion of nutrients required by a crop.

Will cause less damage to crops due to excessive nutrition.

Holds soil intact.

Cheaper.

​Organic Fertilizers

Which one is better?

Eutrophication

• Run off of fertiliser from farmland enters the water and causes increased growth of algae and water plants

• The resulting ‘algal bloom’ blocks sunlight so water plants on the bottom start to die, as does the algae when competition for nutrients becomes too intense

• As water plants and algae die in greater numbers, decomposing bacteria increase in number and use up the dissolved oxygen whilst respiring aerobically

• As a result there is less oxygen dissolved in water, so aquatic organisms such as fish and insects may be unable to survive

Multiple Choice

Why does a plant need a fertilizer?

• to remove pests

• to be strong

• to get its mineral nutrition

• to get rid of weeds

Multiple Choice

Name a mineral that is commonly needed by a plant

• chlorine

• phosphorus

• iron

• fluorine

Multiple Choice

can fertilizers cause pollution?

• yes

• no

• don't know

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Fish Farming

Benefits of fish farming

•Most fish are caught in the wild, however overfishing has lead to dramatic declines of many fish populations

•Fish farms are ways of raising large numbers of fish in a small space to provide food (protein) for humans

•This has several advantages over wild caught fish, including:

•ability to selectively breed fish to ensure high quality, fast growing fish

•ability to protect against predators

•ability to control water quality (many wild caught fish have significant levels of pollutants such as mercury in their flesh)

•ability to control feeding to ensure rapid growth

​Deforestation

Consequences

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