WAEC Agriculture 2020
Questions & Answers

Distractor check: Learners might confuse decomposition with weathering or erosion, but those processes involve physical rock breakdown or soil movement rather than organic decay. Reasoning to the answer: Decomposition is carried out by biological agents like bacteria and fungi to break down organic matter, which ultimately yields humus to enhance soil structure and fertility. Common mistake: Confusing the biological breakdown of organic matter into humus with inorganic weathering processes.

Distractor check: Students might think of budding or grafting since they are common tree-crop practices, but cocoa relies primarily on a different propagation method for nurseries. Reasoning to the answer: Cocoa (Theobroma cacao) is predominantly propagated using seeds planted in nurseries because this approach preserves genetic diversity and remains cost-effective for large-scale farming. Common mistake: Assuming all tree crops are propagated vegetatively through cuttings rather than seeds.

Distractor check: Candidates might choose deeper planting depths like 3-5 cm or more, which are suitable for larger seeds but detrimental to rice establishment. Reasoning to the answer: Rice seeds must be sown at a shallow depth of 1-2 cm to guarantee rapid germination and emergence, since placing them deeper causes poor crop establishment and lower yields. Common mistake: Planting rice seeds too deeply, which hinders proper emergence.

Distractor check: Students often default to nitrogen, which promotes vegetative leaf growth, but reproductive development requires a different primary nutrient. Reasoning to the answer: Phosphorus is essential for energy transport via ATP and robust root development, making it the key nutrient that directly drives seed and fruit formation in plants. Common mistake: Confusing nitrogen's role in vegetative growth with phosphorus's role in seed and fruit formation.

Distractor check: Learners might select hydroponics or aquaponics, which involve water and nutrients, but miss the specific detail about roots suspended in a mist. Reasoning to the answer: Aeroponics suspends plant roots directly in the air and applies a nutrient-rich mist, which maximizes oxygen access and accelerates nutrient uptake for faster growth. Common mistake: Confusing aeroponics, which uses a mist, with general hydroponics where roots are submerged in liquid.

Distractor check: Students might pick root rot, leaf blight, or anthracnose, which affect yams or other crops, but are not viral in origin. Reasoning to the answer: Yam mosaic virus causes mottled foliage, reduced yields, and stunted growth in yams (Dioscorea spp.), and it is spread primarily by aphids or infected planting stock. Common mistake: Confusing fungal or bacterial yam afflictions with the yam mosaic virus.

Distractor check: Candidates might point to rainfall, temperature, or human activity as primary drivers, overlooking the fundamental geological foundation of soil. Reasoning to the answer: Parent material, consisting of underlying rock or sediment, supplies the original minerals that dictate soil composition and govern how quickly weathering transforms it into soil. Common mistake: Overlooking the foundational role of parent material in favor of climatic factors when considering soil formation.

Distractor check: Students might consider goats, sheep, or pigs, but these livestock types are raised primarily for meat or milk rather than egg production. Reasoning to the answer: Ducks (Anas platyrhynchos domesticus) are specifically raised for high-volume egg production, yielding larger eggs than chickens alongside quality meat. Common mistake: Assuming poultry like ducks are kept exclusively for meat instead of recognizing their high egg yield.

Distractor check: A student might choose erosion or tilling, but those describe natural degradation or cultivation rather than the mechanical removal of the upper layer for land use. Reasoning to the answer: Topsoil stripping involves the deliberate mechanical removal of the nutrient-dense topsoil layer for activities like mining or construction, which destroys fertility if neglected. Common mistake: Confusing natural soil erosion with intentional topsoil stripping for industrial projects.

Distractor check: Options like drying, smoking, or salting use dehydration or curing, but the prompt specifically highlights cooling as the preservation method. Reasoning to the answer: Freezing exposes vegetables to temperatures below -18°C to stop enzymatic action and microbial growth, thereby maintaining their texture and nutritional value over time. Common mistake: Confusing freezing with drying or other methods that do not rely on low-temperature cooling.

Distractor check: Candidates might confuse inbreeding with crossbreeding or outcrossing, which involve mixing different breeds or lines rather than keeping matings strictly within the same breed. Reasoning to the answer: Inbreeding involves mating closely related animals within the same breed to lock in desirable traits, though it carries the trade-off of increasing homozygosity and genetic abnormalities. Common mistake: Confusing inbreeding within a single breed with crossbreeding different breeds.

Students might mistakenly choose Zinc, Copper, or Iron because they are all well-known plant nutrients. However, Sulphur is the correct macro-element because plants require it in larger quantities than micronutrients, making it essential for protein synthesis—such as forming amino acids like cysteine—as well as for chlorophyll formation. Common mistake: confusing macronutrients, which are needed in larger amounts, with micronutrients required only in trace amounts.

Apiculture or Pisciculture might look plausible to students thinking of general animal-rearing industries like bees or fish. The correct answer is Sericulture, which specifically involves the rearing of silkworms like Bombyx mori on mulberry leaves to produce silk cocoons, serving as a key agro-industry across many Asian countries. Common mistake: mixing up specialized animal rearing terms like sericulture for silkworms and apiculture for bees.

Students might incorrectly pick leaf drop or stunted roots, thinking of general stress responses in crops. The right choice is interveinal chlorosis, which happens because manganese is vital for photosynthesis and enzyme activation, leading to yellowing specifically between the veins while the veins themselves stay green in young leaves. Common mistake: assuming all nutrient deficiencies cause overall leaf loss rather than specific patterned discoloration like interveinal chlorosis.

Deep ploughing or slash and burn might seem like effective ways to clear or manage land quickly. Minimum tillage is actually the most sustainable choice for small farms because it reduces soil disturbance, thereby preserving soil structure, organic matter, and microbial life while minimizing erosion and boosting long-term sustainability. Common mistake: confusing intensive land clearing techniques with sustainable practices that preserve soil structure.

Options like Elephant grass or Guinea grass are common grasses that might mislead students looking for forage types. Stylo is the correct answer because it is a tropical legume used as forage, which fixes nitrogen to boost soil fertility while simultaneously supplying high-protein feed for livestock. Common mistake: failing to distinguish between standard tropical grasses and leguminous forage crops that fix nitrogen.

Students might lean toward Rickets or Scurvy due to familiarity with vitamin deficiencies in general. Anemia is the correct answer because a lack of vitamin B12 leads specifically to pernicious anemia in animals, which impairs the production of red blood cells and results in fatigue, weakness, and poor growth. Common mistake: attributing general vitamin-related bone or tissue disorders like rickets or scurvy to vitamin B12 instead of blood-related anemia.

Increases pest infestation or encourages erosion might be chosen by someone misinterpreting agricultural management practices. Improving soil fertility is correct because crop rotation systematically alternates crops to replenish nutrients—such as legumes fixing nitrogen—while also suppressing weeds and pests and enhancing overall soil health for sustained productivity. Common mistake: assuming that rotating crops would degrade soil quality rather than replenish it.

Students might mistakenly select Extensive system or Ranching, confusing confined settings with open grazing. Intensive system is correct because it confines animals in barns or pens with high-output feeds, maximizing production per unit area though it demands careful waste management. Common mistake: mixing up extensive and intensive livestock farming systems regarding confinement and feed inputs.

Whitefly, Aphid, or Mealybug might seem plausible if students think of general sap-sucking plant pests. Stem borer is the correct choice because the larvae of the sugarcane stem borer, Chilo sacchariphagus, specifically tunnel into the stems, causing wilting, reduced juice content, and yield losses reaching up to 30%. Common mistake: confusing general sap-feeding insects with stem-boring larvae that physically tunnel into crop stalks.