Agricultural Science Paper 2, Nov/Dec 2010  
Questions: 1 2 3 4 5 6 7 8 9 10 Main
General Comments

Question 5

((a) What are ornamental plants?                                                                [2 marks]

(b) List five factors that influence the choice of a crop nursery site.              [5 marks]

(c) Give two examples of each of the following methods of weed control:

(i) Physical method;                                                                                  [2 marks]
(ii) biological method;                                                                               [2 marks]
(iii) cultural method.                                                                                 [2 marks]

(d) Give three functions of potassium in crops.                                              [3 marks]


This question was not popular with the candidates and the performance of the few that attempted it was discouraging.

In question 5(a), most ofthe candidates could not define ornamental plants. However, in question 5(b), many candidates could list the factors that influence the choice of a crop nursery site.

In question 5{c), most of the candidates were unable to give examples of physical, biological and cultural methods of weed control. Further to this, most of the candidates could not give the functions of potassium in crops as demanded in question 5 (d).

The expected answers include:

Meaning of ornamental plants

Ornamental plants are grown for their aesthetics, that is, their beauty, order and attractiveness.

Examples of methods of weed control
Physical method
- Hand pulling
- Hoeing and spudding
- Tillage
- Mowing and slashing
- Flooding
- Smothering with non-living materials

Biological method
- Use of moth/beetle of Cactoblastic cactorum to control prickly pear (opuntia spp.)
 - Use of ruminants such as goat and sheep to graze e.g. oil palm plantation
- Planting of leguminous crops such as Centrosema spp and Calapogonium spp on uncropped land

Cultural method
- Mulching
- Crop rotation
- Proper spacing
- Use competitive crops
- Burning

Functions of Potassium in crops
- It is an essential constituent of plant tissues
- It aids synthesis of carbohydrate
- It activates various plant enzyme reactions
- It promotes the development of young plants
- It is necessary for neutralization of organic acids in plants
- It helps in nitrate uptake from the soil
- It is associated with stomata movement and therefore influences water relationship



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