a)(i) Give two examples of each of specimens A and B. (2 marks) (ii) State three advantages of the application of specimen Ain crop production. (3 marks) (i...

(a)(i) Examples of the specimens (specimen A being an organic manure and specimen B an inorganic fertilizer):

• Specimen A (organic manure): poultry droppings and cow dung (also compost or green manure).
• Specimen B (inorganic fertilizer): NPK 15:15:15 and urea (also sulphate of ammonia or single superphosphate).

(a)(ii) Three advantages of applying specimen A (organic manure) in crop production:

1. It improves soil structure and increases the water-holding capacity of the soil.
2. It adds humus and releases its nutrients slowly over a long period.
3. It improves soil aeration and encourages the activity of useful soil organisms.

(a)(iii) Two methods of applying specimen B (inorganic fertilizer):

1. Broadcasting (spreading it evenly over the field).
2. Band or ring placement near the plant (or foliar spraying of soluble types).

(b) Percentage of water in the soil samples. Working from the recorded masses:

(b)(i) Mass of fresh soil = (mass of crucible + fresh soil) - mass of crucible.

• Sample C = \( 100 - 80 = 20 \) g
• Sample D = \( 140 - 80 = 60 \) g

(b)(ii) Mass of water = (mass of crucible + fresh soil) - (mass of crucible + soil after heating), that is the loss on heating.

• Sample C = \( 100 - 95 = 5 \) g
• Sample D = \( 140 - 100 = 40 \) g

(b)(iii) Percentage of water \( = \dfrac{\text{mass of water}}{\text{mass of fresh soil}}\times100 \).

• Sample C \( = \dfrac{5}{20}\times100 = 25\% \)
• Sample D \( = \dfrac{40}{60}\times100 = 66.67\% \)

(c) There is an inverse (antagonistic) relationship between the amount of water and the amount of air in the soil: both share the same pore spaces, so as the water content rises the air content falls, and vice versa.