(a) State four characteristics of clay. [4 marks] (b) Mention four effects of drought on plant growth and development [4 marks] (c) List two symptoms of pho...

(a) Four characteristics of clay

• It has very fine particles (less than 0.002 mm).
• It has high water-holding capacity and drains poorly (poor aeration).
• It is sticky and plastic when wet, and hard/cracks when dry.
• It is heavy to work (heavy soil) and generally high in nutrients (high cation exchange capacity).

(b) Four effects of drought on plant growth and development

• Wilting and eventual death of plants.
• Stunted growth and reduced yield.
• Shedding of leaves, flowers and fruits (premature ripening).
• Reduced germination and poor nutrient uptake (nutrients cannot dissolve without water).

(c) Two symptoms of phosphorus deficiency in crops

• Purplish/reddish colouration of the leaves and stem.
• Stunted growth with poor root development and delayed maturity.

(d) Importance of soil properties in crop production

(i) Soil reaction (pH):

• It determines the availability of plant nutrients in the soil.
• It affects the activity of soil micro-organisms (for example nitrogen-fixing bacteria).
• It influences which crops can grow well, since crops have preferred pH ranges.

(ii) Soil temperature:

• It affects the rate and speed of seed germination.
• It influences the rate of root growth and nutrient/water absorption.
• It affects the activity of soil micro-organisms and the rate of decomposition of organic matter.