(a) (i) Explain the term surface drainage. (ii)List three disadvantages of surface drainage (b)(i) Define irrigation. (ii) State two aims of irrigation. (ii...

Answer Details

(a)(i) Surface drainage. It is the removal of excess water from the surface of the land by directing it into open channels, ditches, drains or furrows that carry the water away, usually by shaping and sloping the land so that water flows off freely. It prevents water-logging of the topsoil.

(ii) Three disadvantages of surface drainage:

1. The open channels and ditches occupy land that could otherwise be cropped.
2. The channels can cause soil erosion and gullying as the flowing water carries away topsoil.
3. They require regular cleaning and maintenance, since they easily become blocked by weeds and silt.

(b)(i) Irrigation. Irrigation is the artificial application of water to the soil (crops) through pipes, channels or sprinklers to supplement rainfall and provide the moisture needed for plant growth, especially during the dry season.

(ii) Two aims of irrigation:

1. To supply crops with adequate water for growth where rainfall is insufficient or unreliable.
2. To make dry-season (all-year-round) crop production possible and to increase yields.

(iii) Five problems associated with irrigation:

1. High cost of installing and maintaining irrigation equipment and structures.
2. Build-up of salts in the soil (salinity), which reduces soil fertility.
3. Water-logging of the soil when drainage is poor.
4. It can encourage water-borne diseases (such as bilharzia) and breeding of disease vectors.
5. Scarcity or unreliable supply of water at the source, and silting of dams and canals.