Odisha CHSE +2 VOC Micro Irrigation Technician flashcards

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

Field capacity

Water content of soil after excess water has drained by gravity, held at about -10 to -33 kPa. It is the upper limit of plant-available water and a key design reference for irrigation scheduling.

Permanent wilting point

Soil water content at about -1500 kPa where plants can no longer extract water and wilt permanently. The difference between field capacity and this point gives plant-available water.

Reference evapotranspiration ETo

Evapotranspiration from a well-watered reference grass surface, computed by FAO-56 Penman-Monteith from weather data. Crop water use is ETo multiplied by the crop coefficient Kc.

Readily available water

Fraction p of plant-available water that a crop can use without stress, typically 0.4 to 0.6 of the field capacity minus wilting point range. It sets the irrigation interval.

Wetted bulb shape

Three-dimensional wetted soil volume below an emitter. Sandy soils produce narrow deep bulbs, clay soils wide shallow bulbs, so emitter spacing and discharge must match texture.

Pressure-compensating emitter

Drip emitter that maintains a nearly constant discharge, usually within ten percent, over a wide pressure range of roughly 0.5 to 4 bar. It allows long laterals and level differences.

Media filter

Sand or gravel bed filter that removes fine organic and inorganic particles from surface water. It is backwashed when differential pressure reaches about 0.5 to 0.8 bar.

Air release valve

Valve installed at high points of mains and sub-mains to discharge trapped air. It prevents air locks, protects against water hammer and improves flow stability in the network.

Emission uniformity

Design measure of discharge variation across a drip system, calculated from emitter coefficient of variation and number of emitters per plant. Values of 90 percent or more are targeted.

Lateral flushing velocity

Minimum flow speed at the open lateral end, about 0.3 to 0.5 metres per second, needed to carry out accumulated sediment. Flushing is done at least fortnightly.

Chlorination for clogging

Injection of chlorine to control organic and bacterial clogging of drip emitters and filters. Continuous dosing uses 1 to 2 ppm free chlorine, shock treatment 50 to 100 ppm.

Christiansen uniformity coefficient

Uniformity measure for sprinkler systems computed from the absolute deviations of individual catch depths from the mean. Values of 80 percent or more are generally acceptable.

Sprinkler spacing rule

Recommended spacing of about 50 to 60 percent of wetted diameter along laterals and 40 to 50 percent between laterals. Closer spacing raises uniformity in wind.

Wind effect on sprinklers

Wind above about 3 metres per second distorts sprinkler patterns, causing drift and uneven distribution. Irrigating at night or reducing spacing reduces the effect.

Best efficiency point

Operating point on a pump curve where efficiency is highest. The duty point, where pump curve meets system curve, should lie close to this point for energy savings.

NPSH

Net positive suction head, the absolute pressure margin at the pump suction. Available NPSH must exceed required NPSH to prevent cavitation, noise and impeller damage.

Venturi injector

Fertigation device that uses a pressure drop to draw stock solution into the water line. It is cheap but causes 10 to 30 percent head loss.

Backflow prevention

Check valve and vacuum breaker arrangement that stops fertilizer or chemical solution from flowing back into the water source. It is mandatory for fertigation safety.

Emitter clogging diagnosis

Open emitters at head, middle and tail of laterals and compare discharge. Uniform low flow indicates filter or pressure problems; scattered low flow indicates clogging.

Filter differential pressure

Pressure difference across a filter element, measured by two gauges. A rise of about 0.5 bar signals clogging and the need to clean or backwash.

Goof plug

Small plug used to close an unwanted emitter hole or repair a punctured lateral. It is a standard item in a micro irrigation repair kit.

Drip water quality limits

Guideline values for clogging risk: EC below 1.5 dS/m is safe, pH 6.5 to 8.0, suspended solids below 50 mg/L, iron below 0.5 mg/L and manganese below 0.1 mg/L.

Bicarbonate scaling risk

Bicarbonate above about 2 milliequivalents per litre, or hardness above 200 mg/L as calcium carbonate, indicates calcium carbonate scaling. Acidification controls it.

Solar pump sizing

Pump power is calculated from water density, gravity, discharge and total head divided by pump efficiency. Solar array size must cover peak daily hydraulic energy.

Crop coefficient Kc

Factor that adjusts reference evapotranspiration to a specific crop and growth stage. Values rise from initial to mid-season and decline in late season.

Tensiometer scheduling

Scheduling method using soil matric potential readings. Irrigation is started when the tensiometer reaches a threshold, commonly -30 to -50 kPa for many horticultural crops.

Protected cultivation ET

Evapotranspiration inside a polyhouse or shade net, reduced by roughly 20 to 50 percent compared with open field. Irrigation scheduling must be adjusted to this microclimate.

Per Drop More Crop subsidy

Component of the national micro irrigation programme giving capital subsidy, typically 55 percent for small and marginal farmers and 45 percent for others, with possible state top-up.

Payback period

Capital cost of a micro irrigation system divided by annual net benefit. It shows how many years are needed to recover the investment from increased income or savings.

Annual maintenance contract

Service agreement in which the provider performs scheduled flushing, filter cleaning, chemical treatment and repairs for a fixed annual fee. It is a core micro irrigation service business.

Electrical safety in irrigation

Earthing of pump and controller, use of RCCB or ELCB protection, dry locked panels and never working on live circuits. Water and electricity together make this critical.

Chemical handling safety

Use of gloves, goggles and mask when handling acids, chlorine and fertilizers, with labelled separate storage away from water sources and immediate flushing of skin contact.