MSCE Agriculture flashcards

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

C3 versus C4 photosynthesis

C3 plants fix CO2 directly with RuBisCO into three-carbon compounds, while C4 plants first fix CO2 with PEP carboxylase, reducing photorespiration and improving water-use efficiency in hot climates.

Law of the minimum

Liebig's principle stating that crop yield is limited by the single most deficient growth factor; correcting other factors cannot raise yield until that limiting factor is addressed.

Growing degree days

Accumulated heat units calculated as the sum of daily mean temperature minus a base temperature; used to predict crop development stages and timing of management operations.

Harvest index

The ratio of economic yield to total biological yield; modern semi-dwarf cereals achieve higher harvest index than older tall varieties because more dry matter goes to grain.

Rumen fermentation

Microbial breakdown of fibre and starch in the rumen, producing volatile fatty acids and microbial protein; it lets ruminants use roughage that monogastrics cannot digest.

Metabolic body weight

Body weight raised to the power 0.75, used to express maintenance energy requirements; larger animals need less energy per kilogram of body weight than smaller ones.

Feed conversion ratio

The amount of feed consumed divided by the liveweight gain produced; a lower ratio indicates more efficient conversion of feed into meat, milk, or eggs.

Colostrum

First milk rich in antibodies, fed within the first hours of life so the newborn absorbs passive immunity through the gut before absorption capacity declines.

Cation exchange capacity

The soil's capacity to hold exchangeable cations, measured in cmol(+)/kg; clay and organic matter raise it, improving nutrient retention and buffering against leaching.

Base saturation

The percentage of the cation exchange capacity occupied by exchangeable bases such as calcium, magnesium, and potassium; high values indicate fertile, less acidic soils.

Bulk density

Oven-dry soil mass divided by total soil volume, including pore space; high values indicate compaction that restricts root growth and reduces water infiltration.

Soil erosion equation

The universal soil loss equation: A equals R times K times LS times C times P, combining rainfall erosivity, soil erodibility, slope, cover, and support practice factors.

Gross margin

Gross output from an enterprise minus its variable costs; fixed costs are excluded, so gross margin compares enterprises on returns to the resources they use.

Break-even yield

The yield needed to cover total costs, calculated as total fixed costs divided by the difference between unit price and unit variable cost.

Partial budget

A farm management tool comparing added returns and reduced costs against added costs and reduced returns to decide whether a proposed change is profitable.

Price elasticity of demand

The percentage change in quantity demanded divided by the percentage change in price; staple foods are inelastic, meaning demand changes little when prices rise.

Drawbar power

Power delivered at the tractor drawbar, calculated as draft force in kilonewtons multiplied by forward speed in metres per second; it excludes power lost in wheel slip.

Field capacity of machinery

Theoretical area worked per hour, calculated as working width in metres times speed in kilometres per hour divided by ten, before adjusting for field efficiency.

Wheel slip

The difference between wheel travel under load and travel without load, expressed as a percentage; excessive slip wastes fuel and damages soil structure.

Grain moisture content

The proportion of water in grain, expressed on a wet or dry basis; grain must be dried to a safe storage moisture to prevent mould and insect damage.

Economic threshold

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

A model showing that disease requires a susceptible host, a virulent pathogen, and a favourable environment; removing any one component prevents an epidemic.

Koch's postulates

Four steps proving a pathogen causes a disease: isolate it, culture it, inoculate a healthy host to reproduce symptoms, then re-isolate the same organism.

Integrated pest management

A decision framework combining prevention, monitoring, thresholds, and biological, cultural, and chemical methods, using pesticides only when other tactics are insufficient.

Adopter categories

Rogers' classification of innovation adopters: innovators about 2.5%, early adopters 13.5%, early majority 34%, late majority 34%, and laggards 16%.

Farmer field school

A participatory, season-long extension approach where farmers observe, experiment, and make management decisions in their own fields, building practical problem-solving capacity.

Extension methods

Classified as individual (farm visits), group (demonstrations, field days), and mass media (radio, leaflets); the choice depends on audience size and complexity of the message.

Monitoring and evaluation

Monitoring continuously tracks activities and inputs, while evaluation periodically assesses outcomes and impact against baseline indicators to judge programme effectiveness.

Conservation agriculture

A farming system with three principles: minimum soil disturbance, permanent soil cover with crop residues, and crop rotation or diversification to protect soil and water.

Agroforestry

Deliberate integration of trees with crops or livestock on the same land, providing shade, windbreaks, fertility, and carbon storage, while managing competition for water and light.

Nitrous oxide emissions

A greenhouse gas released from nitrogen fertilizer and manure, with roughly 265 times the global warming potential of carbon dioxide; management aims to match nitrogen supply to crop demand.

Climate-smart agriculture

An approach pursuing three simultaneous goals: increased productivity, enhanced resilience to climate change, and reduced greenhouse gas emissions per unit of output.