Odisha CHSE +2 VOC Micro Irrigation Technician key terms

The water content a soil holds after excess water has drained away by gravity, usually one to three days after rain or irrigation. It marks the upper limit of water readily available to most crops.

The soil moisture level below which a plant can no longer extract water and stays wilted even in a humid atmosphere. It sets the lower limit of plant-available water.

The portion of plant-available soil water that a crop can take up without stress, typically a fraction of the total between field capacity and wilting point. It guides how much to deplete before irrigating.

The share of available soil water a grower permits to be used before the next irrigation. Choosing a smaller value keeps the crop unstressed but increases irrigation frequency.

The water loss from a standard well-watered grass or alfalfa surface, computed from weather data such as temperature, humidity, wind and solar radiation. It is multiplied by a crop coefficient to estimate crop water use.

A dimensionless factor that adjusts reference evapotranspiration to the actual water use of a specific crop at a given growth stage. Values rise from establishment to peak canopy and fall at maturity.

The degree to which emitters in a drip system deliver equal flow rates despite pressure and manufacturing variation. Good uniformity prevents some plants being over-watered while others are under-watered.

A numerical index, usually between 0 and 1, describing how evenly a drip or micro-sprinkler system applies water across the field. Higher values mean a more uniform application and better design quality.

A measure comparing the average depth of water applied in the least-watered quarter of a field to the overall average. It is used to judge sprinkler and drip performance in the field.

A classic sprinkler uniformity formula that sums the absolute deviations of individual catch-can depths from the mean and expresses uniformity as a percentage. Values near 100 percent indicate even water distribution.

A field procedure in which open containers are spaced across a sprinkler-irrigated area to collect water, and the depths are measured to calculate application uniformity and rate. It also reveals wind distortion of the spray pattern.

A drip outlet containing a flexible or moving part that maintains a nearly constant flow over a range of inlet pressures. It allows longer laterals and uneven terrain without large flow differences.

A simple drip outlet whose flow varies with line pressure, typically increasing as pressure rises. It suits short, level laterals where pressure differences are small.

The small-diameter pipe, usually fitted with emitters or micro-sprinklers, that runs along a crop row and delivers water to plants. Laterals connect to larger submain and main lines.

A pipe that distributes water from the main line to a group of laterals, often serving one irrigation block or valve section. Its size is chosen to keep pressure variation within design limits.

A set of laterals operated together by one valve or control point so that the available pump flow is applied to one part of the field at a time. Blocks are sized to match the system flow rate.

The minimum water speed, commonly around 0.3 to 0.5 metres per second, needed in drip lines to carry sediment and biological debris out of the system. It is achieved by opening line ends during flushing.

The proportion of applied irrigation water that must pass below the root zone to keep soil salinity below a damaging level. It is larger when irrigation water is more saline.

A measure of how well water conducts electricity, used as an indicator of dissolved salts. Higher readings warn of salinity risk to crops and of possible emitter clogging.

A pressure vessel filled with graded sand or crushed basalt through which water passes to trap organic matter and fine mineral particles before entering drip lines. It is cleaned by backwashing.

A housing holding a fine mesh cylinder or disc that removes particles larger than the mesh opening from irrigation water. It is often used as a secondary filter after a media filter.

Reversing the direction of water flow through a media or screen filter to dislodge trapped debris and send it to waste. It is done when the pressure difference across the filter rises too far.

A fertiliser injection device with a narrowing throat that creates a suction as water flows through it, drawing concentrate into the irrigation line. It is simple and cheap but causes a pressure loss.

Applying soluble fertiliser through an irrigation system so nutrients reach the root zone with the water. It requires careful injection timing, flushing and backflow prevention to protect the water source.

A device or arrangement of valves that stops irrigation water, fertiliser or chemicals from flowing back into a well, canal or public supply. It is a legal and safety requirement in fertigation systems.

The absolute pressure available at a pump inlet above the liquid's vapour pressure, which must be sufficient to prevent cavitation. It depends on suction lift, pipe friction and water temperature.

The formation and collapse of vapour bubbles in a pump when local pressure drops below vapour pressure, causing noise, vibration, reduced flow and damage to impellers. It is avoided by adequate suction conditions.

A graph showing how a pump's head, flow rate, efficiency and power requirement change across its operating range. It is matched with the system curve to find the actual duty point.

A curve showing the head required to move water through a given piping network at each flow rate, including static lift and friction losses. Where it crosses the pump curve defines the operating point.

Deciding when and how much to irrigate, based on soil moisture, crop water use or plant indicators. Good scheduling saves water and energy while keeping the crop productive.

A sealed tube filled with water and fitted with a porous ceramic tip and vacuum gauge, buried in the root zone to indicate soil moisture tension. It helps growers decide when to start irrigation.

Deliberately supplying less water than the crop's full requirement, often at tolerant growth stages, to save water while limiting yield loss. It requires accurate scheduling and knowledge of crop sensitivity.

Covering the soil surface with plastic film, crop residue or other material to reduce evaporation and suppress weeds. In protected cultivation it is often combined with drip lines placed under the film.

Growing crops under greenhouses, shade nets, low tunnels or similar structures that modify temperature, light, humidity and pest pressure. Micro irrigation is usually essential because rainfall is excluded.

A government grant that pays part of the installation cost of a micro irrigation system, released after approval and verification. It reduces the farmer's upfront investment but may require standards and inspections.

The share of micro irrigation project cost that the farmer must pay after deducting the government subsidy. It is usually collected before installation and documented in the subsidy file.

A document prepared for a micro irrigation subsidy or installation proposal that includes field survey, layout drawing, bill of quantities, cost estimate and expected water savings. It supports approval and inspection.

Clothing and gear such as gloves, goggles, boots and respirators worn to reduce exposure to chemicals, sharp fittings and machinery during installation and maintenance. Its correct use is a basic safety duty.