Few candidates attempted this question. In 4(a) (i-iii), many candidates were unable to define hygroscopic water, capillary water and gravitational water.
In 4(b) and (c ), most of the candidates could state ways in which soil water is important to crops and list ways by which water is lost from the soil.
However, in 4(d), some candidates could not give reasons for transplanting seedlings late in the afternoon.
The expected answers include:
This is the water which is absorbed on the surfaces of soil particles from atmospheric water vapour.
This is the water which rises above the water table in the soil and is held in the fine pores of soil particles by surface tension.
This is the water which can drain from the soil under the influence of gravity.
Reasons for transplanting seedlings late in the afternoon
-The rate of transpiration is very low at that period of the day hence
less water is lost from the plant cells;
-The rate of evaporation of soil water is less during that period thus
the plant roots will be turgid and able to supply the plant with water;
- Temperature at that period is relatively low and helps to prevent
scorching/wilting of the plants by high intensity of sunlight.