Agricultural Science 3 Nov/Dec 2013

Agricultural Science Paper 3,Nov/Dec 2013

Questions:		1	2	3	4		Main

General Comments
Weakness/Remedies
Strength

Question 4

The table below gives details of factors that affect the productivity of a fish pond.
Study it carefully and answer the questions that follow.

Productivity Factors	Details
Organic waste	High
pH range	4.8 – 5.2
Water level	Less than 20% of pond capacity
Sediment	15% of pond capacity
Oxygen content	Low
Plankton population	Low
Aquatic vegetation	Excessive
Turbidity	Very high
Leeches	Abundant

State two management practices that a farmer should undertake to increase the

water level and reduce the amount of sediment in the pond. [ 2 marks ]

2 Mention two steps a farmer should take to increase the oxygen content and

plankton population in the pond. [ 2 marks]

3 State the management practice that should be carried out by a farmer to raise the

pH level and control leeches in the pond. [ 2 marks ]

4 State three demerits of excessive aquatic vegetation in a pond. [ 3 marks]

5 State two measures a farmer could adopt to reduce turbidity of

water in the pond. [ 2 marks]

6 State four factors to be considered in siting a fish pond. [4 marks]

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OBSERVATION

This question was poorly attempted by the candidates. In 4(a), most of the candidates were able to state the management practices that a farmer should undertake to increase the water level and reduce the amount of sediment in the pond, but in 4 (b), majority of them could not mention the steps a farmer should take to increase the oxygen content and plankton population in the pond.
Finally, a good number of the candidates were able to state the management practice that should be carried out by a farmer to raise the pH level and control leeches in the pond but they were unable to state the demerits of excessive aquatic vegetation in a pond as required in 4(c) and (d) respectively. Also, in 4(e), most of the candidates were unable to state the measures a farmer could adopt to reduce turbidity of water in the pond. However, in 4(f), most of the candidates were able to state the factors to be considered in siting a fish pond.
The expected answers include:
(b) Steps a farmer should take to increase the oxygen content and plankton
population in the pond.

            -    Removal of organic waste
            -    Removal of aquatic vegetation/weed control
            -    `Reduction of turbidity of pond water
            -     Increasing the pH level of water in the pond/liming
            -     Fertilization of pond

(d)    Demerits of excessive aquatic vegetation in the pond.
         -     It enhances pond siltation
         -     It makes movement of fish difficult
         -     Leads to undesirable reduction in the temperature of the pond water
         -     It provides refuges for fish predators such as frogs, snakes and crabs
         -     It diminishes the penetration of sunlight into the pond for use by the plankton
                population

(e)    Measures a farmer can adopt to reduce turbidity of water in the pond
         -    Desilting
         -    Weed control
         -    Avoidance of excessive feeding
         -    Liming
         -    Avoidance of over application of organic manure
         -    Construction of dykes around the pond