BGCSE Field Crop Production 1256 flashcards

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

Photosynthesis equation

The process by which green plants use light energy to convert carbon dioxide and water into glucose and oxygen, catalysed by chlorophyll in the chloroplasts.

C3 versus C4 crops

C3 crops such as wheat and rice fix carbon directly with RuBisCO. C4 crops such as maize pre-fix carbon into a four-carbon acid, giving higher water-use efficiency.

Rhizobium symbiosis

Bacteria living in root nodules of legumes convert atmospheric nitrogen into ammonia that the plant can use, supplying much of the crop's nitrogen requirement.

Growing degree days

A heat accumulation measure calculated as the sum of daily mean temperatures above a base temperature, used to predict crop development and maturity timing.

Photoperiodism

The response of plants to day length. Long-day plants flower when days exceed a critical length; short-day plants flower when nights are sufficiently long.

Vernalisation

The requirement for a period of low temperature before flowering, typical of winter cereals and some brassicas, ensuring flowering occurs in the right season.

Critical growth stage

The developmental stage at which a crop is most sensitive to stress such as drought or heat, often flowering and grain filling, where yield loss is greatest.

Soil texture

The relative proportions of sand, silt and clay particles in soil. Texture determines water holding capacity, drainage, aeration and ease of cultivation.

Field capacity

The water content remaining in soil after excess water has drained away by gravity, representing the upper limit of water readily available to plants.

Cation exchange capacity

The ability of soil to hold positively charged nutrient ions on clay and organic matter surfaces. High CEC soils retain nutrients better than sandy soils.

Soil bulk density

The oven-dry mass of soil divided by its total volume. High bulk density indicates compaction, which restricts root growth, water infiltration and aeration.

Fertiliser grade notation

The percentage of nitrogen, available phosphate expressed as P2O5, and potash expressed as K2O in a fertiliser, always written in that order.

Law of the minimum

The principle that crop yield is limited by whichever essential nutrient is in shortest supply, not by nutrients present in excess.

Liming acid soils

Applying ground limestone or dolomite to raise soil pH. Dolomitic lime also supplies magnesium. Over-liming can cause micronutrient deficiencies.

Seed rate calculation

Seed rate in kilograms per hectare equals target plant density times thousand-grain weight, divided by germination and field establishment fractions.

Conservation tillage

A system leaving crop residue on the surface and disturbing soil minimally. It reduces erosion and conserves moisture but needs adapted planting and weed control.

Crop rotation

Growing different crops in sequence on the same land to break pest and disease cycles, manage nutrients and maintain soil structure and fertility.

Intercropping

Growing two or more crops simultaneously in the same field, using complementary canopy and root niches to raise total output and reduce risk.

Mulching

Covering the soil surface with organic or inorganic material to suppress weeds, conserve moisture, moderate temperature and protect against erosion.

Crop coefficient Kc

A factor that adjusts reference evapotranspiration to a specific crop at a given growth stage, used to estimate crop water requirement for irrigation scheduling.

Drip irrigation

Delivering water slowly and directly to the root zone through emitters. It minimises evaporation and foliar wetting and is highly water efficient.

Integrated pest management

A decision framework combining monitoring, cultural, biological and resistant-variety tactics, applying pesticides only when pest numbers exceed economic thresholds.

Economic threshold

The pest population level at which the cost of control equals the value of crop loss that would otherwise occur, justifying treatment.

Disease triangle

The concept that disease occurs only when a susceptible host, a virulent pathogen and favourable environmental conditions coincide at the same time.

Pre-harvest interval

The minimum number of days between applying a pesticide and harvesting the crop, ensuring residues fall within permitted limits for food safety.

Safe grain storage moisture

The moisture content below which grain can be stored without mould growth, commonly around twelve to fourteen percent for cereals and pulses.

Hermetic storage

Airtight storage that depletes oxygen and raises carbon dioxide through respiration, killing or suppressing insects without chemical treatment.

Threshing and cleaning

Separating grain from the ear and then removing chaff, dust and foreign matter, producing a marketable product that stores safely.

Power take-off

A splined shaft on a tractor that transmits engine power to implements such as sprayers and rotavators; it must always be guarded.

Sprayer calibration

Adjusting nozzle output, pressure and travel speed so that the intended dose of chemical is applied uniformly over the field area.

Gross margin

Gross output from a crop, calculated as yield times price, minus the variable costs of producing it. Fixed costs are excluded.

Break-even yield

The yield needed for total enterprise costs to be covered by revenue at a given price, calculated as total costs divided by price per unit.

Contour ploughing

Ploughing along the contour lines of sloping land to slow runoff and reduce soil erosion, a core soil and water conservation practice.

Nutrient budgeting

Comparing nutrients added to a field through fertiliser, manure and fixation with nutrients removed by harvest and losses, to avoid surpluses.

Riparian buffer strip

Vegetated strips beside waterways that trap sediment, nutrients and pesticides from farmland, protecting water quality and stream habitat.