CUET Agriculture flashcards

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

Law of Minimum

Liebig's law states that crop yield is governed by the essential nutrient present in shortest supply relative to plant need; correcting that single limiting factor raises yield most.

Cation exchange capacity

The total negative charge on soil particles that holds exchangeable cations such as calcium, magnesium, potassium and ammonium; measured in cmol(+)/kg and higher in clay-rich or organic soils.

Rhizobium

A symbiotic bacterium that infects legume roots, forms nodules, and converts atmospheric nitrogen into ammonia usable by the plant; the legume supplies carbohydrates in return.

Azolla

A free-floating aquatic fern used in paddy fields; it harbors nitrogen-fixing blue-green algae in leaf cavities and can supply significant nitrogen to rice crops.

Critical period of irrigation

The growth stage when water deficit most reduces yield, typically flowering and grain or fruit filling; ensuring adequate moisture then gives the highest return per unit of water.

Seed rate formula

Seed rate (kg/ha) equals desired plant population per hectare multiplied by test weight in grams, divided by 1000 times germination, purity and field establishment fractions expressed as decimals.

Pre-emergence herbicide

A herbicide applied to the soil before weeds emerge; it forms a chemical barrier in the surface layer and kills germinating weed seedlings, for example pendimethalin or atrazine.

Post-emergence herbicide

A herbicide applied after weeds have emerged and are actively growing; it is absorbed through foliage, for example 2,4-D or glyphosate, and requires correct stage and dose.

Herbicide mode of action

The biochemical process by which a herbicide kills plants, such as photosynthesis inhibition or amino acid synthesis inhibition; rotating modes of action delays resistance evolution in weed populations.

Crop rotation

Growing different crops in sequence on the same land; alternating legumes with cereals and deep-rooted with shallow-rooted crops improves soil fertility and disrupts pest and disease cycles.

Test weight

The weight of a standard volume of seed, usually expressed in grams per 1000 seeds; it is used to calculate seed rate and indicates seed size and plumpness.

Soil pH

A measure of soil acidity or alkalinity on a scale of 0 to 14; it controls nutrient availability, with most field crops performing best between pH 6.0 and 7.5.

Micronutrients

Essential elements needed by plants in very small amounts: iron, manganese, zinc, copper, boron, molybdenum, chlorine and nickel; deficiency or excess both reduce yield.

Macronutrients

Essential elements required in large amounts: nitrogen, phosphorus, potassium, calcium, magnesium and sulfur; carbon, hydrogen and oxygen are supplied mainly by air and water.

Azotobacter

A free-living aerobic soil bacterium that fixes atmospheric nitrogen without a host plant; inoculating seed or soil with it can supply part of the nitrogen needs of non-legume crops.

Field establishment percentage

The proportion of germinated seeds that survive to become established plants in the field; it is lower than laboratory germination because of soil, pest and weather losses.

Green manuring

Growing a quick-growing crop, often a legume, and ploughing it into the soil while still green to add organic matter and nitrogen and improve soil physical properties.

Organic matter

Living, dead and decomposed plant and animal material in soil; it improves structure, water-holding capacity, cation exchange capacity and supplies nutrients on decomposition.

Integrated nutrient management

Combining chemical fertilizers, organic manures, biofertilizers and crop residues to supply nutrients; it maintains soil health and reduces dependence on mineral fertilizers.

Integrated pest management

A strategy combining resistant varieties, cultural, mechanical, biological and chemical methods; pesticides are used only when pest populations exceed economic threshold levels.

Economic threshold level

The pest population density at which control measures should be applied to prevent the pest from reaching the economic injury level and causing unacceptable crop loss.

Biological control

Using natural enemies such as predators, parasitoids and pathogens to suppress pest populations; examples include Trichogramma wasps against stem borers and Bacillus thuringiensis against caterpillars.

Pheromone trap

A trap baited with a synthetic sex pheromone to attract and catch a specific insect species; used for monitoring pest populations and for mass trapping to reduce damage.

Dapog nursery

A rice nursery method in which sprouted seed is sown densely on a polythene sheet or banana leaf and kept moist; seedlings are ready for transplanting in about 12 to 14 days.

System of Rice Intensification

A rice cultivation method using young single seedlings, wide spacing, intermittent wetting and drying, and mechanical weeding; it aims to raise yield with less seed and water.

Consumptive water use

The water transpired by the crop plus that evaporated from the soil surface in the cropped field; it is the main component of crop water requirement.

Drip irrigation

Applying water slowly and directly to the root zone through emitters; it saves water, reduces evaporation and weed growth, and allows fertigation with dissolved nutrients.

Sprinkler irrigation

Spraying water through the air like rainfall from pressurized nozzles; suitable for closely sown crops and undulating land, but not for paddy or crops prone to leaf diseases.

Vermicompost

Organic manure produced by earthworms feeding on organic wastes; it is rich in humus, plant nutrients and beneficial microorganisms and improves soil structure and fertility.

Farmyard manure

A mixture of cattle dung, urine, litter and feed waste decomposed in pits; it supplies organic matter and all major nutrients in small amounts and improves soil physical condition.

Zero tillage

Sowing a crop directly into undisturbed soil with a seed drill after clearing the previous crop; it conserves moisture and soil, saves fuel and time, and reduces erosion.

Allele

One of two or more alternative forms of a gene at the same locus on homologous chromosomes; alleles determine contrasting traits such as tall versus dwarf plant height.