NCEA Level 2 Agricultural and Horticultural Science cheat sheet

Soil texture triangle: sand (>0.05 mm), silt (0.002–0.05 mm), loam (0.002–0.05 mm) and clay (<0.002 mm) proportions determine class; loam balances water retention and drainage.

Soil pH affects nutrient availability: most crops grow best at pH 5.8–6.5; below 5.5 aluminium toxicity and phosphorus lock-up increase, above 7.5 iron, manganese and zinc become less available.

Liming raises pH; the amount needed depends on soil buffer capacity and target pH, so a soil test is required rather than a fixed rate.

Plant macronutrients: N (leaves, protein), P (roots, energy transfer), K (water regulation, fruit quality), plus Ca, Mg, S; micronutrients include Fe, Mn, Zn, Cu, B, Mo.

Nitrogen fixation by Rhizobium in legume root nodules converts atmospheric N2 to plant-available ammonium; clover and lupin are common New Zealand examples.

Nutrient loss pathways: leaching (soluble nitrate below root zone), volatilisation (ammonia from surface urea), runoff/erosion (sediment-bound P) and denitrification (waterlogged soils).

Photosynthesis: 6CO2 + 6H2O + light → C6H12O6 + 6O2; limiting factors are light, CO2, water and temperature, and the slowest factor sets the rate.

Transpiration pulls water and dissolved minerals up the xylem; stomata close under water stress, reducing both transpiration and CO2 uptake.

Plant hormone roles: auxin (cell elongation, rooting), gibberellin (stem elongation, germination), cytokinin (cell division), ethylene (ripening, senescence), abscisic acid (stomatal closure, dormancy).

Fair test design: change one independent variable, measure one dependent variable, hold all other variables (temperature, light, water, cultivar) constant, and repeat to reduce random error.

Valid sampling uses random or systematic placement of quadrats/plots, adequate replicate number, and consistent measurement method; biased sampling (e.g. only edge plants) invalidates conclusions.

Growth rate = (final size − initial size) ÷ time; percentage change = (change ÷ original) × 100 - always state units and time period.

Yield per hectare = total harvested mass (kg) ÷ area (ha); convert units consistently before dividing.

Germination percentage = (seeds germinated ÷ seeds sown) × 100; use at least 20–50 seeds per treatment to reduce the effect of chance.

Reliability is increased by replicates and repeat trials; validity is increased by controlling variables so the test measures what it claims to measure.

Present continuous data as a line graph (time on x-axis) and categories as a bar graph; label axes with quantity and unit and include a title.

Safety and ethics: identify hazards (chemicals, machinery, sharp tools, allergens), use PPE, follow animal welfare and ethical approval requirements, and record consent where people are involved.

Record raw data in a table before processing; keep original observations so calculations and conclusions can be checked.

New Zealand pasture production peaks in spring and is limited by soil temperature, moisture and nitrogen; ryegrass–white clover is the base pasture mix.

Stocking rate = animal demand ÷ pasture supply; overstocking causes pasture depletion and erosion, understocking causes rank pasture and reduced quality.

Grazing management: rotational grazing with rest periods allows leaf regrowth and root recovery; set stocking suits lambing/calving but risks localised overgrazing.

Animal nutrition requires energy, protein, fibre, minerals and water; feed conversion efficiency = product output ÷ feed intake.

Reproduction targets: ewe lambing percentage = (lambs weaned ÷ ewes mated) × 100; calving and lambing are timed to match pasture supply.

Horticultural production factors: cultivar selection, planting density, pruning, pollination, irrigation, pest and disease control, harvest timing and post-harvest cool chain.

Integrated pest management (IPM) combines monitoring, thresholds, biological control, cultural methods and targeted chemicals to reduce resistance and residue risk.

Biosecurity and quality assurance: farm biosecurity plans, NAIT animal traceability, and food safety programmes (e.g. GAP) underpin market access.

Environmental management: nutrient budgets, riparian planting, effluent management and greenhouse gas mitigation (methane from ruminants, nitrous oxide from nitrogen fertiliser).

Inheritance: genes occur in pairs (alleles); dominant alleles mask recessive ones in heterozygotes, and a Punnett square predicts offspring ratios (e.g. 3:1 for a monohybrid cross).

Genotype is the allele combination; phenotype is the observable trait and equals genotype expressed in the environment.

Selection and breeding use estimated breeding values (EBVs) and trait recording to improve production, health and quality traits over generations.

Crossbreeding exploits hybrid vigour (heterosis) for traits such as growth and fertility; inbreeding increases homozygosity and can expose recessive defects.

Reproductive technologies: artificial insemination spreads superior genetics; embryo transfer multiplies offspring from elite females; synchronisation tightens mating and lambing/calving.

Genetic modification and gene editing differ from conventional breeding; in New Zealand they are regulated and require approval, and market acceptance affects use.

Precision agriculture uses sensors, GPS guidance, variable-rate application and data analysis to match inputs to within-paddock variability.

Irrigation scheduling uses soil moisture monitoring and evapotranspiration data to apply water only when the crop needs it, improving water use efficiency.

Technology adoption decisions weigh economic return, labour, environmental impact and compliance with regulations and market requirements.