PSLE Agriculture cheat sheet

Agriculture: Core Concepts and Practices

• Agriculture is the cultivation of crops and rearing of animals for food, fibre and other products; it splits into crop farming (arable) and livestock farming (pastoral).

• Photosynthesis: carbon dioxide + water + light energy → glucose + oxygen, catalysed by chlorophyll in green leaves; glucose is stored as starch or converted to sucrose for transport.

• Soil is a mixture of mineral particles, organic matter (humus), water, air and living organisms; loam, a balanced mix of sand, silt and clay, is generally the most fertile texture.

• Sand drains fast and holds few nutrients; clay holds water and nutrients but drains poorly and compacts; humus improves water retention, structure and nutrient supply in any soil.

• Essential plant nutrients: nitrogen (N) for leaf and stem growth, phosphorus (P) for roots and flowering, potassium (K) for fruit, disease resistance and overall vigour; NPK ratios on fertiliser labels give the percentage of each.

• Germination requires water, oxygen and a suitable temperature; light is not needed by most seeds to germinate but is needed for subsequent seedling growth.

• Pollination transfers pollen from anther to stigma; wind-pollinated crops (maize, rice) have light pollen and exposed stigmas, while insect-pollinated crops (fruit trees, beans) attract bees with colour and nectar.

• Pests and diseases reduce yield; control methods include biological control (natural predators), cultural control (crop rotation, resistant varieties) and chemical control (pesticides, used carefully to limit harm to beneficial insects).