(a)List three edaphic factor that influence crop growth. [3marks]
(b) Explain the following terms as used in soil and water conservation: (i)gravitational water(ii)hygroscopic water [4marks]
(c) State two deficiency symptoms of each of the following nutrient elements in crops:(i)nitrogen; (ii) phosphorus; (iii)potassium [6marks]
(d) State three benefits derived from draining farmlands. [3marks]
Explanation
(a) Edaphic factors that influence crop growth
-Soil pH Soil texture
-Soil structure
-Soil colour
-Soil temperature
-Soil consistency
-Soil type
-Topography
(b)(i)Gravitational water: This is the excess water above field capacity drains out of the soil under the influence of gravity. This type of water is unavailable for plant use OR This is the water held in soil macro pores that drains out under the influences of gravity This type is unavailable for plant use
(ii) Hygroscopic water : This is the water present in an air-dry soil held tightly by soil solids. This type of water cannot be removed by evaporation and roots of higher plants. It is water unavailable for plant use crops
(c)Deficiency symptoms of nutrient elements in Crops
(i) Nitrogen
- Yellowing or leaves
- Stunted growth
- Premature dropping of leave
- Poor formation of fruits and flowers
(ii) Phosphorus
- Purplish coloured leaves
- Scorched leaves
- Stunted growth with few branches
- Lodging of plants due to Poor root development
- Inhibition of flowering, fruit and seed formation
(iii) Potassium
- Mottling, curling and spotting of leaves
- Streaking of older leaves
- Delayed maturity
- Weak and slender stems
- Premature loss of margins
- Browning of leaf margins
(d) Benefits derived from draining farmlands
- Facilitates planting
- Makes tillage operations easy
- Improves soil aeration
- Improves soil temperature
- Allows for cultural practices on the land
- Favours the growth of aerobic soil organisms
- Means of reclaiming land for agricultural purposes/makes more land available for
cultivation
- Helps to flush excess salts from soils
- Enhances seed germination
- Increases the depth of the root zone in the soil.
- Decomposition of plant and animal residues is increased
- Improves soil structure
- Increases soil productivity