RBSE SS Agriculture flashcards

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

Cropping intensity

Percentage ratio of total cropped area to net sown area in a year. Values above 100 percent show that land carries more than one crop annually.

Land equivalent ratio

Sum of intercrop yields of each species divided by their sole-crop yields. A value greater than one shows an intercropping advantage over sole cropping.

Growing degree days

Accumulated heat units calculated as the sum of daily mean temperature minus a base temperature, counted only on days above that base.

Cation exchange capacity

Total quantity of exchangeable cations a soil can hold, expressed in cmol per kilogram. Humus and smectite clays give the highest values.

Base saturation

Percentage of the cation exchange capacity occupied by exchangeable bases such as calcium, magnesium, potassium and sodium. High values indicate less acidic soils.

Bulk density

Oven-dry mass of soil divided by its total volume, expressed in grams per cubic centimetre. It rises with compaction and falls with organic matter.

Test cross

Crossing an individual of unknown genotype with a homozygous recessive parent. The offspring ratio reveals whether the unknown parent is homozygous or heterozygous.

Heterosis

Superiority of a hybrid over its parents, usually expressed as a percentage above the better parent or the mid-parent value for a trait.

Pure live seed

Product of germination percentage and purity percentage divided by one hundred. It expresses the fraction of a seed lot that will produce seedlings.

Backcross breeding

Repeated crossing of a hybrid to one parent to recover that parent's genome while transferring a specific trait from the donor parent.

Layering propagation

A vegetative method in which a stem is rooted while still attached to the parent plant, then separated. Used in guava and litchi.

Precooling

Rapid removal of field heat from harvested produce before storage or transport. It slows respiration and extends shelf life of fruits and vegetables.

Sex expression in cucurbits

The ratio of male to female flowers on a vine. Ethephon sprays promote female flowers while gibberellic acid promotes male flowers.

Economic threshold level

Pest population density at which control should begin to prevent the pest from reaching the economic injury level and causing unacceptable loss.

Disease triangle

Concept stating that disease requires a virulent pathogen, a susceptible host and a favourable environment acting together over a period of time.

Koch's postulates

Four criteria linking a microorganism to a disease: consistent association, pure culture isolation, reproduction of symptoms on a healthy host, and re-isolation.

Feed conversion ratio

Quantity of feed consumed divided by live weight gain or milk produced. A lower ratio means the animal converts feed more efficiently.

Pearson square method

A simple calculation using diagonals to balance two feedstuffs so that the mixture reaches a target crude protein percentage for a ration.

Colostrum

First milk secreted after calving, rich in immunoglobulins and antibodies. It must be fed soon after birth because the newborn absorbs antibodies only briefly.

Gross margin

Gross output value of an enterprise minus its variable costs. Fixed costs are excluded, so it measures returns to the fixed resources used.

Benefit-cost ratio

Present value of project benefits divided by present value of project costs. A ratio above one indicates the investment is financially viable.

Internal rate of return

Discount rate at which the net present value of a project's cash flows equals zero. Projects with higher rates than the opportunity cost are acceptable.

Diffusion of innovations

Process by which a new practice spreads through a farming community over time, from innovators and early adopters to laggards.

Extension demonstration

Field comparison of a recommended practice with the farmer's own practice, used to show a visible yield or income difference to a group.

Participatory rural appraisal

Set of visual and group tools such as transect walks, resource maps and seasonal calendars used with villagers to analyse local conditions and priorities.

Field capacity of machinery

Area covered per unit time, calculated as implement width in metres times forward speed in kilometres per hour divided by ten, giving hectares per hour.

Wheel slip

Difference between wheel revolutions without load and under load, divided by loaded revolutions and expressed as a percentage. Excessive slip wastes fuel and power.

Alley cropping

Agroforestry practice of growing crops in strips between rows of trees or shrubs, whose prunings supply mulch, fodder and green manure.

Silvopasture

Agroforestry system combining trees with pasture and grazing livestock on the same land, providing shade, fodder and diversified income.

Windbreak

Row of trees or shrubs planted across prevailing winds to reduce wind speed, evaporation and crop damage. Protection extends several tree heights downwind.

Integrated nutrient management

Combining organic manures, mineral fertilizers and biofertilizers to meet crop nutrient demand while minimizing losses and maintaining soil fertility.

Carbon sequestration

Removal of atmospheric carbon dioxide and storage as soil organic matter or biomass, increased by residue retention, reduced tillage and permanent cover.