NSSCAS Agricultural Science 8222 flashcards
NSSCAS Agricultural Science 8222 · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Large stock unit
- A standard measure of grazing pressure equal to roughly one 450 kg cow with calf; about 6-7 goats or 5 sheep equal one large stock unit.
- Carrying capacity
- The maximum number of animals a grazing area can support sustainably without degrading the vegetation, usually expressed as hectares per large stock unit.
- Bush encroachment
- The thickening of woody shrubs and trees in rangeland, reducing grass cover and grazing capacity; in Namibia mainly Acacia mellifera and Dichrostachys cinerea.
- Veterinary cordon fence
- A controlled fence separating Namibia's northern communal livestock area from the southern export zone to prevent spread of foot-and-mouth disease.
- Cation exchange capacity
- The total negative charge of a soil that holds exchangeable cations such as calcium, magnesium and potassium; sandy soils have low values and retain nutrients poorly.
- Soil texture
- The relative proportions of sand, silt and clay particles in a soil; it determines water retention, drainage, workability and nutrient-holding capacity.
- Wind erosion
- The removal and transport of topsoil by wind; the dominant erosion process on dry sandy Namibian soils, controlled by surface cover and windbreaks.
- Rhizobium symbiosis
- The association between legume roots and nitrogen-fixing bacteria that convert atmospheric nitrogen into plant-available forms, enriching soil for the following crop.
- Crop rotation
- The planned sequence of different crops on the same land over seasons; it interrupts pest cycles and, with legumes, restores soil nitrogen.
- Pearl millet
- Mahangu, the drought-tolerant staple cereal of northern Namibia, maturing in about 90-120 days and established at the start of the rainy season.
- Critical weed period
- The early crop growth stage, roughly the first four to six weeks after emergence, when weed competition causes the greatest yield loss.
- Integrated pest management
- A combined strategy using resistant varieties, rotation, sanitation, biological control and targeted chemicals, applying pesticides only when thresholds justify them.
- Rumen fermentation
- Microbial breakdown of fibrous feed in the rumen, producing volatile fatty acids and microbial protein that supply most of the ruminant's energy and protein.
- Heterosis
- Hybrid vigour, the superior performance of crossbred offspring over the average of their parents, greatest in the first cross and reduced in later generations.
- Colostrum
- The antibody-rich first milk produced after birth; young stock must consume it within the first hours because gut absorption of antibodies is short-lived.
- Rotational grazing
- A system in which livestock graze paddocks in sequence, allowing each paddock a rest period for vegetation recovery and preventing selective overgrazing.
- Foot-and-mouth disease
- A highly contagious viral disease of cloven-hoofed animals causing mouth and foot vesicles, controlled by movement restrictions, cordon fences and vaccination.
- Anthrax
- A zoonotic bacterial disease causing sudden death with dark blood from body openings; carcasses must not be opened because spores form on air exposure.
- Notifiable disease
- A disease that must by law be reported to the state veterinary authority, such as anthrax, rabies or foot-and-mouth disease, so control measures can be applied.
- Biosecurity
- Measures preventing the introduction and spread of disease on a farm, including quarantine of new animals, disinfection, visitor control and isolating sick stock.
- Gross margin
- Gross income from an enterprise minus its variable costs; fixed costs are excluded so enterprises can be compared per hectare or per animal.
- Break-even yield
- The yield at which total revenue equals total costs, calculated as total fixed costs divided by the difference between unit price and unit variable cost.
- Partial budget
- A farm management tool listing extra costs and reduced returns against extra returns and reduced costs to decide whether a proposed change is profitable.
- Straight-line depreciation
- An annual charge calculated as purchase cost minus salvage value, divided by useful life in years, reflecting the loss in asset value through wear and age.
- Power take-off
- A splined shaft on a tractor that transmits engine power to implements such as mowers and sprayers; the implement must be matched to tractor power.
- Three-point linkage
- The standard tractor hitch with two lower links and a top link that mounts and lifts implements; categories I, II and III differ in pin size and spacing.
- Sprayer calibration
- Setting nozzle output and forward speed so the correct volume of pesticide is applied per hectare, calculated from nozzle flow, boom spacing and speed.
- Conservation agriculture
- A system based on minimum soil disturbance, permanent soil cover and crop diversification or rotation, protecting soil from erosion and conserving moisture.
- Climate-smart agriculture
- An approach that simultaneously raises productivity, strengthens resilience to climate change and reduces greenhouse gas emissions from farming.
- Water harvesting
- Capturing and storing runoff or rainwater using tied ridges, infiltration pits, contour bunds or roof catchment for later use by crops or livestock.
- Independent variable
- In an agricultural experiment, the factor deliberately changed or manipulated by the researcher, such as fertiliser rate, while all other conditions are held constant.
- Composite soil sample
- Several subsamples taken in a zigzag pattern across a field at 0-20 cm depth and mixed, giving one representative sample for laboratory analysis.