(a) ldentify each of specimens N, O, P and Q. (4 marks) (b) Determine the plant population per hectare, if one seed of specimens N is sown per hole at a spa...

(a) Identification of the specimens

• Specimen N is groundnut seeds.
• Specimen O is maize grains.
• Specimen P is guinea corn (sorghum) grains.
• Specimen Q is the aphid.

(b) Plant population per hectare at a spacing of 60 cm x 25 cm

One hectare = 10,000 m². Converting the spacing to metres, 60 cm = 0.6 m and 25 cm = 0.25 m.

Area occupied by one plant = 0.6 m × 0.25 m = 0.15 m².

\[\text{Plant population} = \frac{\text{Area of land}}{\text{Area per plant}} = \frac{10000}{0.15} = 66\,667 \text{ plants per hectare.}\]

Since one seed of specimen N is sown per hole, the plant population is about 66,667 plants per hectare.

(c) Two reasons for including groundnut (the plant from which specimen N is obtained) in crop rotation

• Being a legume, it fixes atmospheric nitrogen in the soil through Rhizobium bacteria in its root nodules, thereby restoring and improving soil fertility.
• Its spreading, ground-covering growth smothers weeds and protects the soil surface, checking erosion.

(d) Three uses of specimen P (guinea corn/sorghum)

• It is used as food for human beings.
• It is used as feed for livestock and poultry.
• It is used in the production of local and alcoholic beverages; the stalks are also used for roofing, staking and as fuel.

(e) Two ways the activities of specimen Q (aphid) affect crops

• The aphids pierce the tender leaves, stems and pods and suck the plant sap, causing distortion of leaves, defoliation and reduced yield.
• They transmit viral diseases from plant to plant as they feed.