LGCSE Agriculture (0179) cheat sheet

Agriculture is the deliberate cultivation of crops and rearing of livestock for food, fibre, fuel and income; it distinguishes itself from hunting and gathering by managed inputs and controlled cycles.

Factors of production in farming are land, labour, capital and management; management coordinates the other three and is the factor most often limiting on smallholder farms.

Climate elements driving farm decisions: rainfall amount and distribution, temperature, humidity, wind, solar radiation and altitude; altitude lowers temperature roughly 6 degrees C per 1000 m rise.

Weather is short-term atmospheric state over hours to days; climate is the 30-year average pattern for a location, so crop choice is a climate decision while planting date is a weather decision.

Farming systems classification: arable (crop), pastoral (livestock), mixed (crop plus livestock), plantation, and aquaculture; intensity ranges from extensive to intensive.

Agricultural environment components: biophysical (soil, water, air, organisms) and socio-economic (markets, credit, extension, tenure, infrastructure, policy).

Ecosystem services from farmland include pollination, nutrient cycling, water infiltration, carbon storage and erosion control; these are outputs not priced in farm gate sales.

Land tenure types include freehold, leasehold, communal and customary; security of tenure affects willingness to invest in long-term improvements such as terracing or tree planting.

Soil texture classes by particle size: sand 2.0-0.05 mm, silt 0.05-0.002 mm, clay below 0.002 mm; the proportions determine a textural triangle class such as sandy loam or clay.

Soil pH ranges: strongly acid below 5.5, near neutral 6.0-7.5, alkaline above 7.5; most arable crops perform best at pH 5.8-7.0, and lime raises pH while gypsum or elemental sulfur lowers it.

Cation exchange capacity (CEC) rises with clay content and organic matter; high-CEC soils hold nutrients such as calcium, magnesium and potassium against leaching.

Soil structure is the arrangement of particles into aggregates; good structure gives stable crumbs, macropores for air and drainage, and resistance to crusting and erosion.

Soil erosion by water follows detachment, transport and deposition; control measures are contour ploughing, terracing, grass strips, mulching, cover crops and windbreaks for wind erosion.

Soil water terms: field capacity is water held after free drainage, permanent wilting point is where plants can no longer extract water, and available water is the difference between the two.

Organic matter improves water holding, structure, CEC and biological activity; it is maintained by manure, compost, crop residues, green manure and reduced tillage.

Nutrient deficiency diagnosis: nitrogen gives pale older leaves and stunting, phosphorus gives purple-tinged leaves and poor roots, potassium gives scorched leaf margins, magnesium gives interveinal yellowing on older leaves.

Soil sampling for analysis follows a zigzag or W pattern across the field, taking 15-20 subsamples from 0-20 cm depth, mixing them and sending a composite sample for laboratory testing.

Crop growth stages: germination, vegetative growth, flowering, grain or fruit filling, maturity; the critical period for yield is flowering to grain filling, when water and nutrient stress is most damaging.

Seed quality criteria are viability (germination percentage), vigour, purity, freedom from pests and disease, and correct moisture content, usually 10-13 percent for stored grain seed.

Planting decisions: spacing determines plant population per hectare, calculated as 10 000 divided by (row spacing in m times within-row spacing in m); depth depends on seed size and soil moisture.

Crop rotation benefits include breaking pest and disease cycles, restoring soil nitrogen with legumes, improving structure, and reducing build-up of allelopathic weeds.

Intercropping and mixed cropping raise land equivalent ratio above 1 when species use complementary resources; they also spread risk of crop failure.

Weed control follows integrated principles: prevention, mechanical cultivation, mulching, crop competition from correct spacing, and selective herbicides applied at the correct growth stage.

Pest management uses integrated pest management: scouting and economic threshold levels, resistant varieties, biological control, cultural methods, and chemicals as a last resort.

Post-harvest losses arise from poor drying, threshing damage, insect and rodent attack, and moisture above safe storage levels; hermetic storage and drying to safe moisture reduce losses.

Ruminants (cattle, sheep, goats) ferment feed in the rumen with microbes, allowing digestion of cellulose in forage; non-ruminants (pigs, poultry) need more concentrated diets.

Feed classification: roughages are high in fibre and low in energy (grass, hay, silage); concentrates are low in fibre and high in energy or protein (cereals, oilseed meals).

Nutrient groups required by livestock are water, energy, protein, minerals and vitamins; water is the most limiting nutrient and intake rises with temperature and milk yield.

Animal breeding tools include selection, crossbreeding for hybrid vigour, artificial insemination, and recording of performance such as growth rate and milk yield.

Signs of oestrus (heat) in cattle: standing to be mounted, restlessness, clear mucus discharge, swollen vulva; the oestrous cycle averages about 21 days in cattle.

Common livestock diseases: foot-and-mouth disease, mastitis, Newcastle disease in poultry, coccidiosis, and internal parasites such as roundworms; vaccination and hygiene are core controls.

Poultry production systems range from free range to deep litter to battery cages; deep litter requires dry absorbent bedding, good ventilation and stocking density control.

Herd health and housing: clean water, dry bedding, ventilation without draughts, isolation of sick animals, and regular deworming and vaccination schedules.

Hand tools by function: hoes for weeding and soil loosening, machetes and slashers for clearing, forks for handling manure, rakes for levelling, and watering cans for irrigation of nursery beds.

Plough types: mouldboard plough inverts soil and buries residues; disc plough works in hard or stony soils; chisel plough loosens without inverting; harrows break clods and level the seedbed.

Tractor power take-off (PTO) transfers engine power to implements such as rotary tillers, balers and sprayers; three-point linkage attaches and lifts mounted implements.

Draft and efficiency: draught requirement rises with soil moisture and depth; wider implements and higher speed raise power demand, so match implement size to tractor power.

Irrigation methods: surface (furrow, basin), sprinkler, drip, and sub-surface; drip gives the highest water use efficiency by delivering water to the root zone.

Pump and water terms: flow rate is volume per unit time, head is the height water must be lifted plus friction losses, and pump efficiency is output power over input power.

Machinery maintenance rules: clean after use, lubricate moving parts, sharpen cutting edges, check bolts and belts, and store under cover to prevent rust and deterioration.

Safety rules for machinery: disengage PTO and stop engine before clearing blockages, wear protective clothing, keep guards in place, and never carry passengers on tractors.

Gross margin equals gross output (yield times price) minus variable costs; fixed costs are excluded, so gross margin compares enterprises on a per-hectare or per-head basis.

Profit equals total revenue minus total costs (variable plus fixed); break-even yield is total costs divided by price per unit of output.

Farm records types: physical records (yields, stock numbers, inputs used) and financial records (receipts, payments, cash book, balance sheet, profit and loss account).

Depreciation spreads the cost of a durable asset over its useful life; straight-line method is (purchase cost minus salvage value) divided by useful life in years.

Marketing functions include assembling, grading, storage, transport, processing, and financing; the marketing margin is the difference between farm gate and retail price.

Price determinants: supply and demand, seasonality, quality grade, distance to market, and number of intermediaries in the chain; a long chain reduces the producer share.

Farm budgeting: partial budget for a single change, enterprise budget for one enterprise, and whole-farm budget for the total business; cash flow budgets track timing of money in and out.

Risk management tools include enterprise diversification, insurance, contract farming, storage to sell off-season, and maintaining a financial reserve.

Photosynthesis converts carbon dioxide and water using light energy into glucose and oxygen; respiration releases energy from glucose, and net dry matter gain is photosynthesis minus respiration.

Limiting factors: Liebig's law states growth is limited by the scarcest resource; adding more of a non-limiting factor does not raise yield.

Nutrient cycles: nitrogen fixation by legumes and free-living bacteria, nitrification, denitrification and leaching; phosphorus cycles slowly through soil and rock with little gaseous loss.

Food chain and trophic levels: producers, primary consumers, secondary consumers, decomposers; energy transfer between levels is roughly 10 percent, so food chains are short.

Biodiversity and agroecology: hedgerows, field margins, cover crops and reduced pesticide use support pollinators and natural enemies of pests.

Conservation agriculture rests on three principles: minimum soil disturbance, permanent soil cover, and crop diversification through rotation.

Sustainability indicators: soil organic matter trend, nutrient balance, water use efficiency, biodiversity, and profitability; a system is sustainable when it meets present needs without depleting the resource base.

Climate-smart agriculture combines increased productivity, adaptation to climate change, and reduction of greenhouse gas emissions where possible.

Field measurement: a rectangular plot area equals length times width; irregular plots are divided into triangles and trapeziums, and area in square metres is divided by 10 000 to give hectares.

Plant population per hectare equals 10 000 divided by (row spacing in m times plant spacing in m); for example 0.75 m by 0.25 m gives about 53 333 plants per hectare.

Experimental design in school projects: control plot, replication, randomisation and uniform treatment; only one variable should be changed at a time to allow valid comparison.

Data collection tools in fieldwork: observation checklists, measurement with tape, ruler, weighing scale and soil auger, and structured interviews with farmers.

Recording and analysis: keep a field notebook with date, activity, inputs and observations; summarise with means, ranges and simple tables, and present results in graphs.

Seed germination test: count 100 seeds, place on moist paper or soil, keep warm and moist, and record the percentage germinated after the recommended period.

Soil and water field tests: jar sedimentation test for texture, hand feel test for texture, and infiltration measured by timing how long a ring of water takes to soak away.

Project report structure: title, introduction and objectives, materials and methods, results, discussion, conclusion and recommendations, plus references and acknowledgements.