WACE ATAR Agricultural Science and Technology flashcards

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

Nitrogen-use efficiency

The percentage of applied nitrogen recovered in harvested product, calculated as nitrogen removed in product divided by nitrogen applied, multiplied by 100.

Eutrophication

Nutrient enrichment of water that triggers algal growth, then decomposition and oxygen depletion, harming aquatic animals; phosphorus usually limits fresh water and nitrogen limits marine systems.

Riparian buffer strip

Vegetated zone beside a waterway that traps sediment and nutrients, stabilises banks and shades streams, reducing runoff pollution entering the water body.

Dryland salinity

Salt accumulation at the soil surface caused by rising water tables after deep-rooted native vegetation is replaced by shallow-rooted annual crops that use less water.

Agroecosystem inputs and outputs

Inputs include solar energy, water, nutrients, seed or stock, labour and fuel; outputs include product, residues, leachate, greenhouse gases and changes in biodiversity.

Yield components

The multiplicative factors producing grain yield, typically plants per square metre, heads or pods per plant, grains per head and average grain weight.

Law of the minimum

Growth is constrained by the scarcest essential resource, so supplying a nutrient that is not limiting produces no yield response and risks off-site loss.

Radiation-use efficiency

The biomass produced per unit of intercepted solar radiation; total biomass equals intercepted radiation multiplied by this efficiency, which varies with crop and conditions.

C3 versus C4 photosynthesis

C3 plants photorespire and suit cooler, wetter climates; C4 plants concentrate carbon dioxide, use water more efficiently and dominate hot, high-radiation environments.

Herbicide resistance management

Rotating and mixing herbicide mode-of-action groups, using multiple effective groups, and preventing seed set by survivors to slow evolution of resistant weed populations.

Plant-available water

Water held between field capacity and permanent wilting point, calculated as the difference in volumetric water content multiplied by rooting depth and adjusted for stones.

Critical soil pH

The range, roughly 5.5 to 7.0 for most temperate crops, where nutrient availability is greatest; below pH 5.0 aluminium toxicity and phosphorus lock-up increase.

Feed conversion ratio

Feed consumed divided by liveweight gain; lower values indicate more efficient conversion, which improves in younger animals and with higher-quality diets.

Rumen microbial fermentation

Microbes in the rumen ferment fibre and synthesise protein from non-protein nitrogen such as urea, provided a readily fermentable energy source is available.

Maintenance energy requirement

The energy needed to sustain an animal at rest without gain or loss, scaling with metabolic body weight raised to the power 0.75.

Conception rate

The proportion of females joined that conceive, calculated as females conceiving divided by females joined, expressed as a percentage of the breeding herd or flock.

Genetic gain per year

Annual improvement in a breeding objective, calculated as selection intensity times accuracy times genetic standard deviation, divided by generation interval.

Inbreeding depression

Reduced fertility, vigour and performance caused by mating related animals, becoming more likely when the effective population size is small.

Five domains of welfare

A framework assessing animal welfare through nutrition, environment, health, behavioural interaction and mental state, extending beyond the earlier five freedoms.

Variable-rate technology

Applying seed, fertiliser or spray at rates that change by location, using a prescription map, GNSS positioning and a controller, with accuracy improved by RTK correction.

Normalised difference vegetation index

NDVI equals near-infrared minus red divided by near-infrared plus red; values near one indicate dense green vegetation, but the index saturates at high canopy cover.

Precision agriculture cycle

A repeating process of sensing variability, mapping it, interpreting the data, applying a variable-rate treatment and then evaluating whether the treatment worked.

Drip irrigation efficiency

Delivering water directly to the root zone, typically achieving 85 to 95 percent application efficiency compared with lower efficiency in furrow and overhead systems.

Sensor calibration and validation

Calibration relates sensor readings to known reference values; validation confirms the relationship holds on independent data, making the sensor useful for decisions.

Soil organic carbon

The carbon stored in soil organic matter, increased by residue retention, reduced tillage and perennial phases, and lost through erosion and continuous cultivation.

Water-use efficiency

Biomass or yield produced per unit of water used from rainfall and irrigation, improved by reducing evaporation, runoff and deep drainage losses.

Whole-farm nutrient budget

Inputs such as fertiliser, feed, fixation and deposition minus outputs in product, leaching, volatilisation and erosion; a positive balance signals accumulation or loss risk.

Integrated pest management

A hierarchy of prevention, monitoring with thresholds, biological control, and targeted chemical control used last, reducing reliance on pesticides and slowing resistance.

Gross margin

Gross income minus variable costs for an enterprise; fixed costs are excluded, allowing comparison of enterprises per hectare or per head.

Break-even yield

The production level at which total costs equal total income, calculated as total costs divided by the price received per unit of product.

Partial budget

A planning tool comparing added returns plus reduced costs against added costs plus reduced returns to decide whether a specific change is financially worthwhile.

Opportunity cost

The value of the next best alternative forgone when a resource is used for one purpose; it belongs in enterprise comparison although no cash changes hands.