Explanation:
(a) Difference between subsistence agriculture and commercial agriculture
Subsistence Agriculture

Production is mainly for family consumption
Less capital is required
Uses family labour/unskilled labour
Use of local breeds of animals
Use of local crop varieties
Hardly use agro-chemicals/Cultural methods are used to control pests and diseases
Records are rarely kept Use of primitive/local tools
Poor housing facilities for rearing animals
Peasant farmers are involved
Doer not require improved processing facilities
Does not involve any marketing Uses crude storage facilities
Yield per unit area is low
Food crops are produced
Small area of land is cultivated
Use of inorganic fertilizers is limited

Commercial Agriculture

Production is mainly for sale
Huge amount of capital is required
Skilled/hired labour is employed
Use of exotic/improved breeds of animals
Use of improved crop varieties
Mostly use agro-chemicals
Records are kept Mechanized/use of machines
Modern housing facilities for rearing animals
Farmers involved may be rich
Requires improved processing facilities
Requires organised market Uses modern storage facilities
Yield per unit area is high
Cash crops are produced
Large area of land may be cultivated
Frequent use of inorganic fertilizers

(b) Advantages and Disadvantages of sources of farm power
(i) Wind :
Advantages
- Running cost is low
- Wind is safe to use
-Wind is a renewable source of energy
- Wind power is environmentally friendly
Disadvantages
-Wind energy converters work only during windy period and as such lie idle during less windy months/ Excessive variation in wind regimes can adversely affect the cost effectiveness of wind energy
-Too weak a wind force cannot be used for any work Success in exploitation of wind energy highly depends
on the specific site
- Wind mills occupy a large portion of land
- Requires high technical expertise
- Initial cost may be high
(ii) Internal Combustion Engine:
Advantages
- It is versatile/can be used for many farm operations
- Efficient source of power
-Not weather dependent
Disadvantages
-A high capital investment is required
- It requires specialized skills in its operation and maintenance
- In developing countries, there is inadequate spare parts for machines
-It contributes to the degradation of the environment/ It Exhaust gases pollute the environment
-Use is subject to to vagaries of fuel shortage
(iii) Electricity
Advantages:
-A very efficient source of farm Power
-it is versatile, with many valued uses
- It is a clean source of power •
-A large amount of energy can be supplied
- It is a fairly reliable source of farm Power
Disadvantages
-High capital outlay to set up
- Very dangerous to operate
- In developing countries, supply cannot be guaranteed at all time
-Needs technical know-how '
-Maintenance cost is high