NCEA Level 2 Agricultural and Horticultural Science flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Soil texture

The relative proportions of sand, silt and clay particles in soil, determined by particle size. Texture controls water retention, drainage, aeration and workability, and is not easily changed.

Soil structure

The arrangement of soil particles into aggregates or peds, creating pore spaces for air and water. Good structure improves root penetration, drainage and resistance to erosion.

Cation exchange capacity

The soil's capacity to hold positively charged nutrient ions such as calcium, magnesium and potassium on clay and organic matter surfaces. Higher CEC means greater nutrient retention.

Leaching

The downward movement of soluble nutrients, especially nitrate, through the soil profile below the root zone with drainage water. It reduces fertiliser efficiency and can contaminate groundwater.

Rhizobium

A soil bacterium that forms nodules on legume roots and converts atmospheric nitrogen into plant-available ammonium. This symbiotic fixation reduces the need for nitrogen fertiliser.

Transpiration

The loss of water vapour from plant leaves through stomata, creating tension that pulls water and dissolved minerals up the xylem from the roots.

Photosynthesis

The process in chloroplasts where light energy converts carbon dioxide and water into glucose and oxygen. It supplies the carbohydrate that drives plant growth and yield.

Abscisic acid

A plant hormone that increases under drought stress, causing stomata to close and promoting seed dormancy. It reduces water loss but also limits carbon dioxide uptake.

Limiting factor

The factor in shortest supply that restricts a process such as photosynthesis or growth. Raising other factors will not increase the rate until the limiting factor is addressed.

Independent variable

The factor deliberately changed by the investigator in an experiment. All other variables must be held constant so any measured change can be attributed to it.

Dependent variable

The factor measured in an experiment in response to the independent variable, such as plant height, germination count or yield. It must be measured consistently with stated units.

Control group

A comparison treatment that does not receive the experimental treatment, kept under identical conditions. It shows what would happen without the variable being tested.

Replication

Repeating a treatment multiple times within an experiment. Replicates reduce the influence of random variation and allow the reliability of results to be assessed.

Reliability

The consistency of results when a measurement or trial is repeated. It is improved by adequate replication, careful technique and repeating the whole experiment.

Validity

Whether an experiment measures what it claims to measure. It requires controlling confounding variables and using appropriate measurement methods for the hypothesis.

Random sampling

Selecting sample points without bias, for example using random coordinates in a quadrat survey. It allows results to be generalised to the whole population or paddock.

Germination percentage

The proportion of sown seeds that germinate, calculated as germinated seeds divided by seeds sown, multiplied by 100. It indicates seed viability and sowing rate.

Yield per hectare

The harvested product mass divided by the area grown, expressed as kilograms or tonnes per hectare. It allows fair comparison between paddocks, crops or treatments.

Stocking rate

The number of animals carried per unit area of land, often expressed as stock units per hectare. It must match pasture growth to avoid overgrazing or wasted feed.

Stock unit

A standard measure of feed demand, based on a mature ewe rearing one lamb. It allows different classes of livestock to be compared and feed budgets to be calculated.

Rotational grazing

A system where stock graze paddocks in sequence and each paddock rests to allow leaf regrowth and root recovery. It improves pasture persistence and utilisation.

Lambing percentage

Lambs weaned per 100 ewes mated, calculated as lambs weaned divided by ewes mated, multiplied by 100. It measures flock reproductive performance.

Feed conversion efficiency

The amount of product (meat, milk or eggs) produced per unit of feed consumed. Higher efficiency means less feed is needed per unit of output.

Integrated pest management

A control approach combining monitoring, economic thresholds, biological control, cultural practices and targeted pesticides. It reduces chemical use and slows resistance development.

Biosecurity

Measures that prevent the introduction and spread of pests and diseases on a farm or in a region. It protects production, animal welfare and market access.

Riparian planting

Planting vegetation along waterways to filter sediment and nutrients from runoff, stabilise banks and shade streams. It reduces nutrient and sediment loss from farmland.

Post-harvest cool chain

Rapid cooling and consistent low-temperature storage after harvest. It slows respiration, ripening and spoilage, maintaining quality during transport and storage.

Dominant allele

An allele whose trait is expressed in a heterozygote, masking the effect of the recessive allele. Dominant alleles explain the 3:1 ratio in a monohybrid cross.

Punnett square

A grid used to predict the genotypes and ratios of offspring from a cross. Parent alleles are placed on each axis and combined in the cells.

Estimated breeding value

A prediction of an animal's genetic merit for a trait, based on its own records and those of relatives. It allows selection decisions to be compared across herds.

Hybrid vigour

The improved performance, such as growth or fertility, shown by crossbred offspring compared with inbred parents. It results from increased heterozygosity and is not passed on reliably.

Precision agriculture

The use of sensors, GPS guidance, variable-rate application and data analysis to match inputs such as fertiliser and water to within-paddock variability, improving efficiency.