HSC Agriculture flashcards

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

Law of the minimum

Yield is constrained by the single most limiting factor, such as water or nitrogen, rather than by total inputs. Supplying non-limiting factors does not raise production.

Growing degree days

A heat accumulation measure calculated as the sum of daily mean temperatures above a crop's base temperature. It predicts flowering, maturity, and pest emergence timing.

C3 versus C4 plants

C3 plants photorespire and lose efficiency in heat; C4 plants concentrate carbon dioxide, giving higher water-use efficiency and growth at high temperatures and light.

Critical soil pH

The pH range where nutrient availability and root growth are near optimal, typically 5.5 to 6.5 in calcium chloride. Below it, aluminium toxicity and phosphorus lock-up occur.

Crop rotation benefit

Alternating crop species interrupts pest and disease life cycles and balances soil nitrogen. Legumes fix nitrogen via rhizobia, reducing fertiliser dependence for following cereals.

Seed dormancy

A state where viable seed fails to germinate despite favourable conditions. It is broken by stratification, scarification, light, or after-ripening, spreading germination over time.

Herbage quality decline

As pasture matures, the leaf-to-stem ratio falls and fibre content rises, lowering digestibility and protein. Grazing at the right growth stage preserves feed value.

Net dry matter production

Gross photosynthesis minus plant respiration. It represents the carbon actually accumulated as biomass and is the basis of yield in crop and pasture systems.

Dry matter intake

The mass of feed dry matter an animal consumes daily, often expressed as a percentage of body weight. Quality and digestibility strongly influence intake.

Rumen volatile fatty acids

Fermentation products absorbed by ruminants: acetate from fibre, propionate from starch, butyrate from sugars. Their ratio determines energy supply and milk fat response.

Metabolisable protein

The protein available to the animal after rumen fermentation, comprising microbial protein and undegraded dietary protein absorbed from the small intestine.

Feed conversion ratio

Feed consumed divided by liveweight gain. A lower value indicates more efficient conversion of feed into animal product and better enterprise profitability.

Body condition score

A subjective fatness scale, commonly one to five or one to eight. Extremes delay return to oestrus and lower conception rates in breeding females.

Colostrum timing

Newborn animals must receive colostrum within six to twelve hours. Gut absorption of immunoglobulins falls rapidly, so late feeding leaves the young vulnerable to disease.

Cattle gestation length

Cattle average about 283 days of pregnancy, sheep about 147 days. Knowing these intervals supports joining dates, pregnancy diagnosis, and calving or lambing planning.

Heat stress in cattle

Above roughly 25 to 30 degrees Celsius, cattle pant and reduce feed intake, lowering milk yield. Shade, water, and airflow mitigate the production loss.

Gross margin

Gross income minus variable costs for an enterprise. Fixed costs are excluded, allowing comparison of enterprise performance and allocation of limited land and labour.

Return on assets

Operating profit divided by total farm assets. It measures how efficiently capital is used, independent of how the business is financed or structured.

Break-even yield

The output required for total revenue to equal total costs. It sets the minimum production or price needed before an enterprise generates profit.

Cash flow versus profit

Profit matches income and costs to a period; cash flow tracks actual receipts and payments. Seasonal farms can be profitable yet short of cash at certain times.

Depreciation

The allocation of an asset's cost across its useful life. It is a non-cash fixed cost that affects taxable income and informs machinery replacement decisions.

Water-use efficiency

Yield or gross value produced per megalitre of water applied. Scheduling irrigation to replace evapotranspiration improves it and limits deep drainage and salinity.

Nutrient budget

A comparison of nutrients entering the farm, through fertiliser, fixation, and manure, with those removed in product. It guides fertiliser rates and identifies surpluses.

Farm diversification

Adding enterprises to spread price, climate, and market risk. It stabilises income but increases management complexity and demands labour and capital capacity.

Controlled experiment

A trial where one independent variable is deliberately changed, all other conditions are held constant, and the dependent variable is measured to test a hypothesis.

Replication and randomisation

Repeating treatments and assigning them randomly reduces bias from uncontrolled variation. Together they allow valid comparison and statistical analysis of results.

Testable hypothesis

A prediction stated before an experiment that can be supported or rejected by data. Experimental results support or fail to support hypotheses; they never prove them.

Farm gate return

The retail price minus all downstream costs such as processing, transport, and retail margin. It shows what the producer actually receives for the product.

Value adding

Processing, grading, packaging, or branding a product to raise its unit price. It requires capital and market access and should be assessed on marginal return.

Sustainability indicators

Measurable signals of long-term viability, including soil organic carbon, ground cover, biodiversity, nutrient balance, and profitability. No single indicator is sufficient.

Risk management tools

Instruments such as diversification, forward contracts, insurance, and enterprise mix. They reduce the variability of farm income rather than raising average returns.

Dependent variable

The response measured in an experiment, such as yield or weight gain. It is compared across treatments to determine whether the independent variable had an effect.