BSEH SS Agriculture flashcards

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

Land Equivalent Ratio

The ratio of land area needed in sole cropping to the area needed in intercropping to produce the same yield; values above one indicate an intercropping advantage.

Cation Exchange Capacity

The total quantity of exchangeable cations a soil can hold, expressed in cmol(+)/kg; humus and 2:1 clays give high values, sands and kaolinite low values.

Economic Threshold Level

The pest population density at which control action should be taken to prevent the pest from reaching the economic injury level and causing unacceptable loss.

Disease Triangle

The concept that a plant disease requires a susceptible host, a virulent pathogen and a favourable environment to occur; removing any one factor prevents the disease.

Rumen Fermentation

Microbial breakdown of fibrous feed in the rumen into volatile fatty acids, with synthesis of microbial protein and B vitamins that the animal later digests.

Field Capacity Formula

Theoretical field capacity in hectares per hour equals implement width in metres multiplied by forward speed in kilometres per hour, divided by ten.

Crop Water Requirement

The depth of water a crop needs, calculated as reference evapotranspiration multiplied by the crop coefficient, adjusted for effective rainfall and losses.

Price Elasticity of Demand

The percentage change in quantity demanded divided by the percentage change in price; demand is inelastic when the absolute value is below one.

Gross Margin

The gross output value of an enterprise minus its variable costs; used to compare enterprises and guide resource allocation on the farm.

Heritability

The proportion of total phenotypic variance attributable to genetic variance; high heritability means selection for the trait is effective and rapid.

Backcross Breeding

Repeated crossing of a hybrid to one parent to recover that parent's genotype while transferring a specific desirable gene, such as disease resistance.

Break-Even Point

The output level at which total revenue equals total cost, calculated as fixed costs divided by the difference between unit price and variable cost per unit.

Partial Budget

A farm planning tool that compares added returns and reduced costs against added costs and reduced returns for a single proposed change.

Law of the Minimum

Liebig's principle that crop yield is limited by the essential nutrient in shortest supply relative to need, regardless of other nutrients present.

Universal Soil Loss Equation

A = R x K x LS x C x P, predicting annual soil loss from rainfall erosivity, soil erodibility, slope, cover management and support practice factors.

Land Capability Classification

A system grouping soils by their suitability for cultivation and the conservation practices required, from class I with few limitations to class VIII unsuitable for crops.

Ecosystem Services

Benefits people obtain from ecosystems, including pollination, nutrient cycling, water filtration and carbon sequestration, many of which agriculture depends on and can supply.

Complete Metamorphosis

Insect development through egg, larva, pupa and adult stages, as in butterflies and beetles; the larva usually causes the crop damage.

Integrated Pest Management

A decision framework combining monitoring, thresholds, cultural, mechanical, biological and chemical tactics, with pesticides used only when justified.

Grafting Union

A propagation technique joining a scion to a rootstock so their cambium layers connect and grow together, combining desirable canopy and root traits.

Climacteric Fruit

Fruit that continues to ripen after harvest with a rise in respiration and ethylene production, such as banana, mango and tomato.

Total Digestible Nutrients

A measure of feed energy value for livestock, summing digestible carbohydrate, protein and fat (fat multiplied by 2.25) expressed as a percentage.

Lactometer Reading

A test of milk specific gravity, normally about 1.026 to 1.032, used to detect added water or removal of fat from the sample.

Duty of Water

The area of land irrigated per unit discharge of water, usually expressed in hectares per cubic metre per second, over a crop season.

Delta of Water

The total depth of irrigation water, usually in centimetres, required by a crop over its entire base period from sowing to harvest.

Marketing Margin

The difference between the price paid by the final consumer and the price received by the producer, covering all marketing functions and intermediaries.

Diffusion of Innovations

The spread of a new practice through a farming community over time, following an S-shaped adoption curve from innovators to laggards.

Seed Certification Classes

Breeder, foundation, registered and certified seed, each a successive generation produced under inspection to preserve genetic purity and quality.

Heterosis

The superior performance of a hybrid compared with its parents, exploited commercially in maize, sorghum, millet and many vegetable crops.

Enterprise Budget

A planning statement listing expected returns, variable costs and fixed costs for one farm enterprise, used to estimate profitability and compare options.

Straight-Line Depreciation

An annual charge equal to the purchase cost minus salvage value, divided by the useful life in years, applied to machinery and farm buildings.

Conservation Tillage

Any tillage system that leaves at least thirty percent of the soil surface covered by crop residue after planting, reducing erosion and conserving moisture.

Seed Germination Test

A laboratory test in which counted seeds are placed on moist substrate under controlled conditions and normal seedlings are counted as a percentage.