TEST OF PRACTICAL KNOWLEDGE QUESTION (a) Give the botanical name of each of specimens I (Common wireweed) J (coatbuttons), K (Giant star grass), and L (cogo...

Answer Details

(a) Botanical names of the specimens

• I (Common wireweed): Sida acuta
• J (Coat buttons): Tridax procumbens
• K (Giant star grass): Cynodon plectostachyus (also accepted Cynodon nlemfuensis)
• L (Cogongrass / spear grass): Imperata cylindrica

(b) Description of Specimen K (Giant star grass)

• A perennial grass that spreads by creeping stolons (runners) which root at the nodes to form a dense mat.
• It produces erect flowering stems bearing finger-like (digitate) spikes arranged in a star shape at the top, from which its name is derived.
• Leaves are narrow, flat and green; the plant is drought tolerant and propagated vegetatively.
• It is a valuable fodder and pasture grass, palatable to livestock.

(c) Preparing silage from Specimen K

1. Harvest the grass at the flowering stage when it is succulent and nutritious.
2. Chop the herbage into small pieces to aid compaction.
3. Wilt slightly to reduce excess moisture.
4. Fill the chopped grass into a silo (pit or trench) in layers.
5. Compact each layer firmly to expel air and create anaerobic conditions.
6. Add molasses to supply extra carbohydrate for fermentation.
7. Seal the silo air-tight with polythene sheet and soil.
8. Anaerobic bacteria ferment the sugars to lactic acid, which lowers the pH and preserves the material. It matures in about 3 to 6 weeks as silage.

(d) Two methods of controlling Specimen L (cogongrass)

• Repeated deep ploughing and tillage to expose and destroy the underground rhizomes.
• Application of a systemic herbicide such as glyphosate to kill the whole plant including the rhizomes; slashing before flowering and smother-cropping with cover crops are also effective.