NZ Scholarship Agricultural and Horticultural Science flashcards

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

Limiting factor

The single resource in shortest supply relative to need, which caps growth regardless of other resources; identifying it is the first step in diagnosing a yield gap.

Yield gap

The difference between the potential yield set by climate and cultivar and the actual yield achieved on a farm, caused by water, nutrient, pest, or management limits.

Cation exchange capacity

A soil's capacity to hold exchangeable cations, rising with clay and organic matter; higher CEC means greater nutrient retention but can also mean slower drainage.

Economic threshold

The pest density at which the cost of control equals the value of the yield that would otherwise be lost, so control is justified only above this density.

Integrated pest management

A hierarchy of prevention, monitoring, thresholds, biological control, and judicious chemical use, designed to suppress pests while limiting resistance and off-target harm.

Nutrient budget

A comparison of nutrient inputs such as fertiliser, feed, and fixation against outputs such as produce, leaching, and volatilisation; a surplus signals loss risk.

Nitrate leaching

Downward movement of nitrate beyond the root zone into groundwater, driven by surplus nitrogen, drainage, and urine patches; it is a diffuse contaminant and a health risk.

Eutrophication

Nutrient enrichment of waterways, especially by phosphorus and nitrogen, causing algal blooms, oxygen depletion, and loss of aquatic biodiversity and recreational values.

Life cycle assessment

A method that inventories inputs and emissions across a product's whole supply chain and assesses impacts per chosen functional unit, such as per kilogram of milk.

Multi-criteria analysis

A decision tool that scores and weights several incommensurable objectives, such as profit, emissions, and animal welfare, to compare options when no single metric dominates.

Sustainability pillars

The four dimensions used to judge a practice: economic viability, environmental integrity, social acceptability, and intergenerational equity, which must be assessed together.

Urine patch

A concentrated point of nitrogen deposition from grazing animals, exceeding plant uptake and creating a hotspot for nitrate leaching and nitrous oxide emission.

Soil texture triangle

A diagram classifying soil by the proportions of sand, silt, and clay, which together determine water-holding capacity, aeration, infiltration, and nutrient retention.

Base saturation

The proportion of exchange sites occupied by base cations rather than hydrogen and aluminium; it rises with pH and indicates nutrient supply and acidity status.

Soil pH and nutrient availability

The soil reaction that governs nutrient solubility; phosphorus is most available near pH 6.0–6.5, while manganese and boron become limiting at high pH.

Liebig's law of the minimum

The principle that growth is determined by the scarcest resource, so adding a nutrient that is not limiting produces no yield response and wastes input.

Radiation use efficiency

The dry matter produced per unit of intercepted solar radiation; combined with canopy light interception, it underpins estimates of crop dry matter accumulation.

Leaf area index

The leaf area above a unit of ground area; it determines light interception, and optimum values balance maximum capture against self-shading and disease risk.

Crop rotation

A planned sequence of different crops on the same land that breaks pest and disease cycles, restores nitrogen via legumes, and improves soil structure.

Monoculture risk

Continuous cropping of one species builds up soil-borne pathogens and selects for herbicide-resistant weeds, increasing reliance on chemical control and reducing resilience.

Herbicide resistance

The inherited ability of a weed population to survive a herbicide dose that once controlled it, selected by repeated use of one mode of action and managed by rotation.

Mode of action rotation

Using herbicides with different target sites in sequence or mixture to prevent selection of resistant weed biotypes and to preserve chemical efficacy.

Stocking rate

The number of animals grazed per unit area; raising it increases output per hectare but lowers per-head intake and performance and raises environmental pressure.

Feed conversion efficiency

The units of feed required to produce a unit of product such as meat, milk, or eggs; higher efficiency lowers cost and emissions per unit of output.

Metabolisable energy

The energy in feed available to the animal after accounting for losses in faeces, urine, and gas; it sets the ceiling on production such as milk or growth.

Body condition score

A visual and tactile assessment of fat cover used to manage feeding and reproduction; extremes reduce fertility and indicate mismatched nutrition and demand.

Soluble solids

A measure of sugars and other dissolved compounds, commonly reported as Brix, used to predict fruit flavour, maturity, and storage potential.

Controlled atmosphere storage

Storage with reduced oxygen and elevated carbon dioxide to slow respiration and ripening; incorrect gas levels cause fermentation, off-flavours, and tissue damage.

Ethylene management

Controlling the ripening hormone through ventilation, separation, and avoidance of mixing climacteric and non-climacteric produce, to slow senescence and extend shelf life.

Cold chain

The unbroken sequence of cooling and refrigerated handling from harvest to consumer; any break accelerates quality loss and increases post-harvest waste.

Diffuse pollution

Contaminants released from many dispersed sources, such as farmland runoff, rather than a single pipe; control therefore targets land use and management practices.

Functional unit

The reference quantity in life cycle assessment, such as per kilogram of product or per hectare, which determines how impacts and system comparisons are expressed.