Agricultural Science 2015 Jamb Examination

Human power is the most basic form of farm power and is readily available. It is easy to control and causes little damage to crops or implements. However, its greatest disadvantage is that the energy output is very low compared to animal or mechanical power. Human labour can only cover a limited area and tires quickly, making it inefficient for large-scale farming.

A magnetic compass is an instrument that shows direction with respect to the Earth's magnetic field. In surveying, it is used to establish or find the bearing of a base line, which is the main reference line from which other measurements are taken. An abney level is for measuring slope or gradient, a plumb bob ensures vertical alignment, and ranging poles are used for marking points, not direction.

Micro-nutrients such as zinc, copper, manganese, molybdenum, and boron are essential for plant growth but are required in very small amounts compared to macro-nutrients like nitrogen, phosphorus, and potassium. Their main role is to activate enzymes and support physiological processes, not directly promoting pest resistance or being fixed by microbes. Hence, their defining feature is their requirement in very small quantities.

Soil texture refers to the relative proportion of sand, silt, and clay, while structure describes how soil particles are arranged into aggregates. Both directly influence pore size and thus determine how much water the soil can hold and make available to plants. Soil pH affects nutrient availability but not water retention, and colour is only an indicator of organic matter or drainage, not a determinant of water-holding capacity.

Soil organisms thrive best in soils with good texture, structure, and organic matter. Soil pH and temperature both affect microbial activity, while higher organic matter increases microbial population. The false statement is that soil with good texture and structure cannot harbour soil microbes, since these are in fact ideal conditions for them to flourish.

Bush burning can temporarily add potash to the soil and may destroy some weed seeds, but its most harmful effect is the destruction of valuable soil organic matter. Organic matter improves soil fertility, structure, and water-holding capacity. Once it is destroyed, soil productivity declines, making this the most significant disadvantage of the practice.

Leguminous crops such as calopogonium, pueraria, and centrosema form symbiotic relationships with Rhizobium bacteria, which fix atmospheric nitrogen into nitrates, enriching the soil. Exoriepus, however, is not a legume and does not contribute significantly to soil nitrate enrichment.

The distribution of cattle depends on the availability of pastures for grazing, rainfall which influences pasture growth, and the presence or absence of diseases like trypanosomiasis. Light does not play any direct role in cattle distribution, hence it is not a determining factor.

Poaching is the illegal hunting or capturing of wildlife, and prohibiting it in game reserves is aimed at conserving wildlife populations. Conservation ensures the survival of endangered species, maintains biodiversity, and preserves ecological balance. The aim is not to reduce populations or starve hunters, but to protect and conserve wildlife.

At field capacity, the soil holds water in small pores after gravitational water has drained away. This water is called capillary water, and it is available for plant roots to absorb. Hygroscopic water is tightly bound to soil particles and unavailable to plants, while gravitational water drains quickly beyond the root zone. Superfluous water is not a recognized category in soil science.