(a) State four functions of each of the following macro-nutrients in plant nutrition: (i) nitrogen; (ii) phosphorus; (iii) potassium. [12 marks] (b) List fo...
Question 1 Report
(a) State four functions of each of the following macro-nutrients in plant nutrition: (i) nitrogen; (ii) phosphorus; (iii) potassium. [12 marks] (b) List four factors that affect the availability of nutrients to crops. [4 marks]
Answer Details
(a) Four functions of each macro-nutrient in plant nutrition
(i) Nitrogen
- Promotes vegetative growth and the development of leaves and stems.
- Forms an essential part of proteins, enzymes and protoplasm.
- Is a constituent of chlorophyll, giving leaves their green colour.
- Improves the quality and yield of leafy crops.
(ii) Phosphorus
- Promotes healthy root development and establishment of seedlings.
- Aids flowering, fruiting and seed formation, hastening crop maturity.
- Is involved in energy transfer within the plant (as part of ATP).
- Strengthens the plant and improves resistance to disease and lodging.
(iii) Potassium
- Strengthens stems and straw, reducing lodging.
- Aids the formation, movement and storage of carbohydrates and sugars.
- Improves resistance to diseases and to drought.
- Regulates the opening and closing of stomata and the water balance of the plant.
(b) Four factors that affect the availability of nutrients to crops
- Soil pH (acidity or alkalinity).
- Soil moisture content.
- Soil temperature.
- Presence of soil organic matter and micro-organisms (and soil texture/aeration).
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