Agricultural Science 2021 Jamb Examination

Land preparation follows a sequential process to ensure the soil is suitable for planting. It begins with land clearing to remove vegetation and obstacles, followed by ploughing to turn and loosen the soil. Harrowing then breaks down the large soil clods, creating a fine tilth, and ridging completes the preparation by forming raised rows for planting.
This sequence ensures proper aeration, drainage, and root development for crops.

The theodolite is a precision optical instrument used in surveying to measure horizontal and vertical angles accurately.
It is essential in determining boundaries and creating maps.
Measuring tape and Gunter’s chain measure distances, while an Abney level measures slopes, not angles.
Thus, only the theodolite is specifically designed for angle measurement in surveying.

Transplanting, which involves moving seedlings from a nursery to the main field, is typically done by hand in most farming systems.
Other operations like planting, fertilizer application, and bush clearing can be mechanized using machinery such as planters, spreaders, and tractors.
Hence, transplanting remains largely a manual operation and is not fully mechanized.

Mechanized agriculture focuses on using machinery to improve efficiency and productivity.
The primary aim is to enable the cultivation of large areas of land with minimal human labour, increasing yield and production speed.
Although it can indirectly reduce production costs, the main purpose is large-scale cultivation and higher efficiency in farming operations.

Maize is a direct-seeded crop, meaning seeds are planted directly into the field rather than raised in nurseries.
Essential operations like weeding, thinning, and fertilizer application promote healthy growth and yield.
Since nursery practices are unnecessary for maize, they are not part of its cultivation process.

Ginning is the process of separating cotton fibres from their seeds using a machine called a cotton gin.
This process is essential before spinning the fibres into yarn.
Other crops like cocoa, oil palm, and palm kernel oil undergo entirely different processing methods such as fermentation or pressing, not ginning.

Ginger is propagated vegetatively using rhizomes, which are underground stems containing buds that sprout new plants.
This method ensures that the new plants maintain the genetic qualities of the parent.
Unlike seeds or tubers, rhizomes grow horizontally underground and are ideal for ginger propagation.

Stylosanthes gracilis is a tropical forage legume, not an animal legume.
It is propagated by seeds, resistant to drought, and produces root nodules that fix atmospheric nitrogen, enriching the soil.
Therefore, the statement that it is an 'animal legume' is incorrect because legumes are plants, not animals.

Planting different varieties of timber is a positive forest management practice that enhances biodiversity and ensures sustainability.
Problems of forest management include lack of information, poor government support, and destruction by bush fires.
Therefore, option C is not a problem but a beneficial practice.

Root-knot disease in tomato plants is caused by nematodes, specifically species of *Meloidogyne*.
These microscopic worms invade the roots, causing galls or knots that hinder water and nutrient uptake.
Viruses, bacteria, and fungi cause other plant diseases but not root-knot disease.