BGCSE Agricultural Science 1517 cheat sheet

Soil texture is the relative proportion of sand, silt and clay; soil structure is the arrangement of soil particles into aggregates.

Soil pH is measured on a 0-14 scale; a pH below 7 is acidic, above 7 is alkaline, and 7 is neutral.

Cation exchange capacity (CEC) is the soil's ability to hold exchangeable cations; clay and organic matter raise CEC.

Field capacity is the water remaining after gravity drainage; permanent wilting point is the water content at which plants cannot extract water.

Available water capacity equals field capacity minus permanent wilting point.

Water erosion begins with splash erosion and can develop into sheet, rill and gully erosion; contour ploughing and cover crops reduce it.

Legumes form nodules with Rhizobium bacteria and fix atmospheric nitrogen, increasing soil nitrogen for later crops.

Compost improves soil structure, water retention and microbial activity; a carbon-to-nitrogen ratio near 25-30:1 favours rapid decomposition.

Germination requires a viable seed, adequate moisture, oxygen and a suitable temperature; some species also need light or scarification.

Seed rate depends on desired plant population, seed weight, germination percentage, purity and expected field establishment.

Crop rotation alternates crops from different families; legumes can restore nitrogen while cereals and root crops use different soil layers.

Transplanting gives a more uniform stand than direct sowing and reduces the period of competition from weeds in the field.

Tillage prepares a seedbed, incorporates residues and controls weeds, but excessive tillage damages soil structure and organic matter.

The critical weed-free period for many annual crops is the first four to six weeks after emergence.

Irrigation scheduling can use soil moisture depletion or estimated evapotranspiration; waterlogging reduces root aeration.

Grain is usually safe for storage at about 12-14% moisture; higher moisture favours mould and insect damage.

Ruminants have a four-compartment stomach: rumen, reticulum, omasum and abomasum; rumen microbes digest cellulose.

Monogastric animals have a simple stomach and cannot efficiently digest large amounts of fibrous roughage.

Inbreeding increases homozygosity and can reveal undesirable recessive traits; crossbreeding exploits heterosis or hybrid vigour.

Approximate gestation periods are 280 days for cattle, 150 days for sheep and goats, 114 days for pigs, and 21 days incubation for chickens.

Feed conversion ratio equals feed consumed divided by live weight gain; a lower ratio means more efficient production.

Colostrum contains antibodies and is needed soon after birth because young animals absorb antibodies poorly after the first day.

Stocking rate is the number of animals per unit area; overstocking leads to overgrazing and pasture degradation.

A crush or race restrains animals for examination and treatment while reducing injury to animals and handlers.

The disease triangle consists of a susceptible host, a pathogen and an environment that favours disease.

Vaccines stimulate immune memory; live vaccines usually replicate in the body, while killed vaccines do not.

A notifiable disease must be reported to veterinary authorities; examples include foot-and-mouth disease, anthrax and rabies in many countries.

Internal parasites are controlled with anthelmintics; underdosing can select for drug-resistant worms.

External parasites include ticks, mites and lice; dipping, spraying and pasture rotation reduce infestation.

Quarantine separates new or sick animals from the herd to limit transmission of infectious agents.

Common signs of illness include reduced feed intake, fever, abnormal dung, isolation and sudden weight loss.

A zoonosis is an animal disease transmissible to humans, such as brucellosis, rabies and anthrax.

Integrated pest management combines cultural, biological, physical and chemical controls, with pesticides used only when needed.

The economic threshold is the pest density at which control cost equals the value of damage prevented.

Pesticide labels state dose rate, pre-harvest interval, safety precautions and target pests; label directions define legal use in many jurisdictions.

Chewing insects remove leaf tissue, while sucking insects pierce plants and remove sap; the damage type helps identify the pest.

Crop rotation, resistant varieties and field sanitation reduce the carry-over of pests and pathogens.

Biological control uses predators, parasitoids or pathogens; broad-spectrum insecticides can kill these natural enemies.

Fungal spores germinate readily in humid conditions; wider plant spacing and improved air flow reduce leaf wetness.

Pesticides are stored away from food and water, and empty containers are triple-rinsed and disposed of according to local rules.

A plough is used for primary tillage, while a harrow is used for secondary tillage to break clods and level the seedbed.

The tractor power take-off (PTO) transfers engine power to implements; the hydraulic system raises and lowers mounted equipment.

Knapsack sprayer output is calibrated using nozzle flow, walking speed and spray swath width so the intended dose per hectare is applied.

Routine machinery maintenance includes checking engine oil, filters, belts, tyres and lubrication points.

A greenhouse protects plants from pests and weather and allows temperature, humidity and light to be managed.

Shade netting reduces light intensity and temperature and protects seedlings from strong sun and hail.

PTO shafts must have guards, and the engine must be stopped before clearing blockages or adjusting implements.

Drip irrigation applies water near the root zone and is generally more water-efficient than overhead sprinklers or furrow irrigation.

Profit equals total revenue minus total cost; gross margin equals gross output minus variable costs.

Fixed costs such as rent, insurance and depreciation do not change with output in the short run; variable costs such as seed and fertilizer do.

Break-even yield equals total fixed costs divided by the difference between price per unit and variable cost per unit.

Farm records include production, financial, labour and inventory records and are used for planning, credit and monitoring performance.

Cash flow records show the timing of money received and paid; profit is not the same as cash because of credit and inventory changes.

Straight-line depreciation equals purchase cost minus salvage value, divided by useful life in years.

A budget estimates expected costs and returns before an enterprise is started or expanded.

Market price, quality grade, demand and transport costs affect the price a farmer receives.

Ecosystem services include pollination, nutrient cycling, water regulation and soil formation; agriculture depends on them.

Biodiversity improves ecosystem resilience; monocultures can allow pests and diseases to spread rapidly.

Conservation agriculture uses minimum tillage, permanent soil cover and crop rotation.

Agroforestry integrates trees with crops or livestock and can provide shade, windbreaks, fodder and fruit.

Mulching reduces evaporation, moderates soil temperature and protects the soil surface from raindrop impact.

Overgrazing compacts soil, reduces plant cover and increases runoff and erosion.

Fertilizer and pesticide runoff can pollute water bodies; buffer strips of vegetation trap sediment and nutrients.

Biogas digesters convert animal manure into combustible gas and a nutrient-rich residue.

Horticulture includes the production of fruits, vegetables and ornamental plants.

Sexual propagation uses seeds; asexual propagation uses cuttings, grafting, budding, layering or tissue culture.

Grafting joins a scion to a rootstock; the rootstock can provide disease resistance, vigour control or adaptation to soil.

Plant breeding methods include selection, hybridization, mutation and genetic engineering.

F1 hybrid seed comes from crossing two inbred lines; saved seed from the F1 may segregate and lose uniformity.

Pruning removes old or diseased wood and improves light penetration and air movement through the canopy.

Nursery seedlings are hardened off by gradual exposure to field conditions to reduce transplant shock.

Cooling, grading and proper packaging after harvest reduce respiration, water loss and mechanical damage.

A representative soil sample is taken in a zig-zag pattern from several points, mixed, and reduced by quartering to a subsample.

Plant population per hectare can be estimated by counting plants in a quadrat of known area and multiplying to a hectare basis.

Germination percentage equals germinated seeds divided by total seeds sown, multiplied by 100.

Plot area in square metres is length times width; one hectare equals 10,000 square metres.

Personal protective equipment for spraying includes gloves, boots, goggles and a respirator, as stated on the label.

Cleaning, sharpening and dry storage reduce rust and wear on hand tools.

A field record for each operation includes date, plot, operation, input rate and observations.

One millimetre of water applied over one hectare equals 10,000 litres.