JCE Agriculture key terms

Tiny pores on the surface of leaves and stems that open and close to let carbon dioxide in for photosynthesis and let water vapour and oxygen out during transpiration.

The loss of water vapour from plant leaves through stomata, which pulls water and dissolved nutrients upward from the roots and cools the plant canopy.

The process by which green plants use sunlight, water and carbon dioxide to make sugars and release oxygen, forming the basis of all crop yield and dry matter production.

The portion of a plant or feed remaining after all water has been removed, used to compare yields and feed value without the distorting effect of moisture content.

The planned sequence of different crops on the same land over successive seasons, used to break pest and disease cycles, manage fertility and reduce soil erosion.

Land left without a crop for one or more seasons so that soil moisture and nutrients can recover and weed, pest and disease pressure declines before the next planting.

A crop grown mainly to be ploughed back into the soil while still green, adding organic matter and nutrients such as nitrogen rather than being harvested.

The resumption of growth by a seed, requiring adequate moisture, warmth and oxygen, ending when the radicle emerges through the seed coat.

The capacity of a seed lot to germinate quickly and produce strong seedlings under field stress, which is distinct from simple percentage germination measured in ideal conditions.

The prepared surface layer of soil where seeds are sown, ideally fine, level, firm and moist so that seed makes good contact with soil and germinates evenly.

A hoofed animal with a multi-chambered stomach and rumen microbes that ferment fibrous plant material, including cattle, sheep and goats.

The largest stomach chamber of a ruminant, where a dense microbial population ferments fibre and produces volatile fatty acids that supply most of the animal's energy.

How willingly and how much an animal eats a particular feed when it is freely available, influenced by taste, smell, texture and previous experience.

The total quantity of feed given to an animal in a day, balanced to supply the energy, protein, minerals and vitamins needed for its age and production level.

The length of time a female carries young from conception to birth, used to plan mating dates and dry-off periods; for example about 283 days in cattle.

The material spread on the floor of a poultry house to absorb droppings and keep birds dry, later valuable as a nutrient-rich soil amendment.

The number of animals kept per unit of area or space, which affects feed intake, growth, disease spread, behaviour and welfare.

The relative proportions of sand, silt and clay particles in a soil, which determine how it holds water, drains and responds to tillage.

The way soil particles clump into aggregates, creating pore space for air, water and roots; good structure resists erosion and is improved by organic matter.

The amount of water a soil retains after excess water has drained away by gravity, representing the upper limit of water readily available to plant roots.

The soil moisture level below which plants can no longer extract water and wilt permanently, marking the lower limit of available water.

The decomposed and decomposing plant and animal residues in soil, which improve structure, water holding, nutrient supply and biological activity.

A measure of soil acidity or alkalinity on a 0 to 14 scale, which controls the availability of nutrients and the suitability of the soil for particular crops.

Applying ground limestone or similar material to raise soil pH and reduce acidity, improving nutrient availability and the effectiveness of some fertilisers.

The physical condition of soil as it affects ease of tillage, root penetration and seedling emergence, with a fine crumb structure described as a good tilth.

The standard tractor mounting system of two lower arms and one top link that lifts and carries implements, with draft and position control.

A splined shaft on a tractor that transmits engine power to driven implements such as rotary tillers, mowers and balers at a standard speed.

A tractor hydraulic system that senses the pull of a ground-engaged implement and raises or lowers it to keep working depth and engine load steady.

Checking and adjusting an implement or sprayer so that it delivers the intended rate, such as seed or chemical per hectare, under field conditions.

A boundary or internal barrier of posts, wire or netting used to contain livestock, exclude animals and mark property lines.

The controlled movement of air through a shed to remove heat, moisture, dust and gases, protecting animal health and reducing condensation and structural damage.

The revenue from a farm enterprise less its variable costs, used to compare the profitability of different crops or livestock before fixed costs are considered.

Expenses that change with the level of production, such as seed, fertiliser, feed and casual labour, and which are deducted to calculate a gross margin.

Expenses that do not vary with the level of output in the short term, such as rent, machinery depreciation and permanent labour.

The level of output or price at which total revenue exactly equals total costs, so the enterprise makes neither profit nor loss.

The detachment and removal of soil by wind or water, accelerated by bare ground, steep slopes and poor management, and controlled by cover, contouring and vegetation.

The downward movement of dissolved nutrients, especially nitrate, through the soil profile beyond the root zone, wasting fertiliser and polluting groundwater.

The enrichment of water bodies with nutrients, mainly nitrogen and phosphorus, causing excessive algal growth, oxygen depletion and harm to aquatic life.

A control strategy combining monitoring, cultural and biological methods with judicious pesticide use to keep pests below damaging levels while reducing chemical inputs.