(a) Describe an experiment to compare the water-holding capacity of sandy, loamy and clayey soils.
(b) List three factors that may affect the water-holding capacity of soils.
(c) (i) State the characteristics of sandy and loamy soils.
(ii) What type of vegetation does each support?
Explanation
(a) To perform an experiment to compare water holding capacity of sandy, loamy and clayey soil, one will need to obtain samples of sandy, loamy and clayey soils, dry soils samples or air dry samples to constant weight, insert funnels in the neck of the three measuring cylinders and place a folded filter paper or cotton wool in each of the funnels, put a known or equal weight of each of the air-dried soils in each of the funnels respectively and label them as sandy, loamy and clayey, pour equal amount of water into each soil and leave the set up till no more drops of water pass through it to the cylinder. Find the differences between the volume of water retained by each soil.
Observation: Sandy soil has more volume of water, followed by loamy soil and clayey soil in the cylinder.
Conclusion: Clayey soil has the greatest water retention capacity followed by loamy soil and sandy soil.
(b) Factors that may affect water holding capacity of a soil are:
(i) Humus content/organic matter/living organisms
(ii) Clay content
(iii) Soil texture.
(iv) size of soil particles
(v) mineral salt and pH
(c)(i) Sandy soil contains silica, large particles, low nutrients and low capillary power, retains little water, is porous / well drained, possesses coarse, gritty or rough texture and large air spaces and its mineral nutrients are easily leached. Loamy soil contains humus, organic matter, a mixture of sand clay and silt in about equal proportion and possesses moderate aeration, capillary power and water holding or retaining capacity.
(ii) Sandy soil supports scanty vegetation, grass or grassland and shrubs while loamy soil supports heavy or luxuriant vegetation (forest).