ZIMSEC Form 4 Agriculture Complete Summary Notes 7 – 8


Intensive subsistence farming     


Rice growing in South East Asia     











O Level and A Level Notes By Subjects and grades (








Rice being grown in SE Asia




Many workers.

Flat land (or sometimes steep terraced hillsides).

Hot and wet monsoon climate.

Limited amounts of fertiliser and pesticide.





Rice (and possibly other crops such as maize).

Some farmers keep animals such as chickens to supplement their diet.

Very little, if any, will be left over to sell and most will feed the farmer and his family.





Rice growing is labour intensive and heavily dependent on high rainfall and hot temperatures.

The growing population means there is a high demand for food which puts pressure on the
farmer to produce two or even three crops a year.






Crops can be affected by disease, which can reduce yields.

Children are often denied basic education because they are required to work on the farms.

This has a long-term impact on the development of the country.

Without enough rain the rice crop fails and there is a lack of food. This can lead to starvation in remote communities.

Soil erosion and salinisation


Soil erosion


This is a problem in parts of the UK that are very flat, such as East Anglia. When the soil is left bare after ploughing, the wind can pick up speed due to the flat land and blow away the unprotected soil.




In addition, hedgerows have been removed from farmland to allow machinery to be used more easily and farm the land more intensively. Hedgerows help to hold the soil together and act as valuable windbreaks.


Consequences of soil erosion in MEDCs




The effects of drought in Africa

If the topsoil (the most productive layer of the soil) is removed, then crop yields can decline.

Loss of biodiversity (a diverse range of wildlife) in rivers – fish species find it difficult to breed because they lay their eggs in the gravel at the bottom of rivers and deposition of sediment smothers the gravel. Eggs that are smothered in

sediment do not receive sufficient oxygen to

Roads and footpaths can become slippery, causing a hazard to walkers, motorists and cyclists.

Drains can become blocked with eroded soil causing localised flooding.

Sediment can find its way into water storage reservoirs, reducing storage capacity for water
supplies and increasing flood risks.

Phosphates (chemicals from fertilisers) in the soil can cause excessive algal growth in rivers, lakes and reservoirs. If the sediment finds its way to an estuary or is dredged and dumped out at sea it can also cause algal growth in marine water. Algal growth causes damage to ecosystems and can be toxic.

Water quality can be reduced – it may require treatment before it becomes fit for human consumption.

The navigability of water courses can be reduced because of deposition of sediment.
Soil erosion is also a problem in

The soil is exposed and vulnerable to erosion as a result of the removal of vegetation and overgrazing.

Trees, which provide protection from the wind and rain, are removed to be used as fuel.

Nomadic tribes have become more sedentary, which puts pressure on the land where they

When soil is blown away the land becomes useless for grazing and crops and causes
desertification. This is a problem in the Sahel region of Africa.








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