Odisha CHSE +2 VOC Micro Irrigation Technician cheat sheet

Soil water potential components: gravitational, matric, osmotic and pressure potentials; plants extract water mainly against matric potential, and only matric potential (not osmotic) is measured by tensiometers.

Field capacity (FC) is water held at about -10 to -33 kPa; permanent wilting point (PWP) is about -1500 kPa. Plant-available water = FC − PWP, expressed in mm per metre depth.

Readily available water (RAW) = p × (FC − PWP), where p is the allowable depletion fraction (commonly 0.4–0.6 for horticultural crops, 0.5 for many field crops).

Reference evapotranspiration ETo is computed by FAO-56 Penman-Monteith; ETc = ETo × Kc, and Kc changes with crop stage (initial, development, mid-season, late season).

Infiltration rate must exceed application rate in micro irrigation; if emitter discharge exceeds soil intake, runoff and deep percolation occur.

Irrigation interval (days) = RAW (mm) ÷ ETc (mm/day). Emitter run time (h) = crop water need (mm) × area per plant (m²) ÷ emitter discharge (L/h).

Soil texture controls wetted bulb shape: sandy soils give narrow, deep bulbs; clay soils give wide, shallow bulbs, so emitter spacing and discharge must be matched to texture.

Water use efficiency (WUE) = marketable yield ÷ water applied; irrigation efficiency = water beneficially used ÷ water delivered, and micro irrigation typically reaches 85–95%.

Typical drip system sequence: water source → pump → check valve/air release → filtration → pressure gauge → fertilizer injection point downstream of filter → main line → sub-main → lateral with emitters.

Drip emitters are classified as inline (integral, factory-spaced) or online (button, pressure-compensating, vortex, micro-tube); PC emitters maintain flow within ±10% over a 0.5–4.0 bar range.

Micro-sprinklers and jets cover 1–5 m wetted diameter with discharge 30–200 L/h; they suit orchards, nurseries and crops needing aerial parts wetted.

Lateral spacing and emitter spacing define wetted percentage Pw; for widely spaced crops, one or two emitters per plant are placed within the root zone.

Head loss along laterals must keep emission uniformity (EU) above 80–90%; allowable pressure variation is typically ≤20% of emitter operating pressure.

Filtration type matches water quality: screen filters for clean water, media (sand) filters for surface water with organic load, hydrocyclone for sand-laden well water, usually followed by a screen.

Air release valves at high points and flush valves at lateral ends prevent air locks and sediment accumulation; vacuum breakers protect against backflow.

Design steps: crop water requirement → ETc and peak ET → emitter selection → irrigation cycle (run time, frequency) → lateral/sub-main/main sizing → head loss and pressure check → pump and filter sizing.

Emission uniformity EU = 100 × (1 − 1.27 CV/√n), where CV is manufacturer's coefficient of variation and n is emitters per plant; EU ≥ 90% is the design target.

Manufacturer's coefficient of variation classes: CV < 0.05 excellent, 0.05–0.07 average, 0.07–0.11 marginal, > 0.11 unacceptable.

Lateral length limit is set by allowable pressure variation (20% of operating pressure) and friction loss; use the Christiansen or Hazen-Williams friction charts.

Flushing velocity in laterals should reach at least 0.3–0.5 m/s at the open end to remove sediment; flush at least once a fortnight or after fertigation.

Commissioning includes pressure testing, flushing all mains and laterals, checking emitter discharge at the head, middle and tail of representative laterals, and recording values.

Chemical treatment: chlorine (1–2 ppm free chlorine continuously or 50–100 ppm shock) for organic clogging; acid (pH 2–3 in laterals) for carbonate scaling; never mix chlorine and acid.

Sprinkler application rate must not exceed the soil's basic infiltration rate; otherwise runoff and soil crusting occur.

Uniformity measures: Christiansen uniformity coefficient (CU) and distribution uniformity (DU); CU ≥ 80% and DU ≥ 70% are acceptable in most field designs.

Sprinkler spacing is normally 50–60% of wetted diameter along the lateral and 40–50% between laterals for rectangular layouts.

Operating pressure determines droplet size and pattern; low pressure gives large droplets and poor distribution, high pressure gives fine droplets prone to wind drift.

Wind speed above 3 m/s distorts the pattern; irrigate at night or in early morning, or reduce spacing in the windward direction.

Rotating impact sprinklers operate at 2–4 bar with discharge 0.5–3 m³/h; micro-sprinklers operate at 1–2 bar with smaller wetted diameters.

Pump head required = operating pressure (m) + elevation difference + friction loss in main, laterals and fittings + safety margin.

Centrifugal pumps suit low-to-medium heads with high discharge; submersible pumps suit deep wells; positive-displacement pumps suit high pressure at low flow.

Pump curves plot head vs discharge; the duty point is the intersection of the pump curve and the system curve, and efficiency is highest near the best efficiency point (BEP).

Net positive suction head (NPSH) available must exceed NPSH required by the pump to avoid cavitation; cavitation causes noise, vibration and impeller damage.

Screen filter mesh: 120–200 mesh (about 75–125 micron) for drip; media filters achieve 50–100 micron equivalent and need backwashing at 0.5–0.8 bar differential pressure.

Fertigation injection rate (L/h) = (desired nutrient concentration × system flow) ÷ stock solution concentration; inject in the middle third of the irrigation cycle and flush after.

Venturi injectors are cheap but cause 10–30% head loss; diaphragm and piston pumps give precise dosing and are driven by water flow or electricity.

Automation uses solenoid valves, controllers, pressure switches and soil moisture or tensiometer sensors; controllers must have a rain sensor and manual override.

Backflow prevention (check valve plus vacuum breaker) is mandatory between the fertilizer tank and the water source to protect drinking water.

Clogging causes: physical (sand, silt), chemical (CaCO3, iron precipitation), biological (algae, bacterial slime). Diagnose by opening emitters at head, middle and tail.

Symptom–cause rule: low pressure at tail laterals → clogged filter or lateral, undersized main or pump wear; uneven discharge → clogged emitters or air lock.

Symptom–cause rule: wet spots at emitter base → damaged or missing emitter; dry plant with wet soil → emitter plugged or lateral disconnected.

Symptom–cause rule: pump not delivering → air leak on suction, clogged impeller, worn seal, low water level, or closed valve.

Routine schedule: daily pressure and flow check, weekly filter cleaning, fortnightly lateral flushing, monthly chlorination when organic load is high, seasonal acid treatment.

Repair kit essentials: spare emitters, goof plugs, lateral joiners, punch tool, end caps, grommets, Teflon tape, pressure gauge and filter elements.

Record keeping: water meter readings, pump hours, filter differential pressure, chemical doses and repair log form the basis of preventive maintenance.

Water quality limits for drip: EC < 1.5 dS/m (safe), 1.5–3.0 dS/m (moderate), > 3.0 dS/m (severe); pH 6.5–8.0; suspended solids < 50 mg/L; iron < 0.5 mg/L; manganese < 0.1 mg/L.

Hardness and bicarbonate: bicarbonate > 2 meq/L or hardness > 200 mg/L as CaCO3 indicates scaling risk requiring acidification.

Water source yield must be checked against peak demand; a borewell yield test (pumping test) gives safe yield in L/s or m³/h.

Storage tank capacity should cover at least one to two days of peak demand and allow settling of sediment; cover tanks to prevent algae.

Energy efficiency: solar pumping systems are sized from hydraulic energy = ρ × g × Q × H ÷ efficiency; use variable frequency drives (VFD) to match pump output to demand.

Energy cost per m³ = (pump power in kW × hours × tariff) ÷ volume pumped; reducing head loss and using efficient pumps lower this figure.

Water harvesting structures (farm ponds, check dams) can supplement micro irrigation; ensure silt traps and screens before the pump.

Crop coefficient Kc stages: initial (0.3–0.5), development (0.7–0.8), mid-season (0.9–1.2), late season (0.6–0.8); ETc = ETo × Kc.

Drip irrigation raises yield and WUE in horticultural crops; it also allows fertigation, which improves nutrient use efficiency and reduces leaching.

Scheduling methods: soil moisture depletion (tensiometer at −30 to −50 kPa for many crops), pan evaporation (Epan × Kp), and ET-based scheduling.

Protected cultivation (polyhouse, shade net, greenhouse) reduces ETo by 20–50%; irrigation scheduling must be adjusted to the modified microclimate.

In a polyhouse, drip with 2 L/h emitters at 30–40 cm spacing and one lateral per crop row is common; relative humidity control reduces disease.

Critical irrigation stages: flowering, fruit set and fruit enlargement are the most sensitive; water stress at these stages reduces yield most.

Mulching with plastic film reduces evaporation and weed growth and is often combined with drip laterals placed under the mulch.

Project cost components: pump, filters, main and sub-main pipes, laterals, emitters, valves, fittings, tank, installation labour, and automation.

Benefit-cost ratio = present value of benefits ÷ present value of costs; payback period = capital cost ÷ annual net benefit.

Subsidy under the national micro irrigation scheme (Per Drop More Crop, PMKSY) is typically 55% for small and marginal farmers and 45% for others, with state top-ups; verify current state norms.

Application process: farmer applies through the state agriculture/horticulture portal → field survey and design → approval → installation by empanelled supplier → joint inspection → subsidy release.

Service business model: annual maintenance contracts, fertigation services, system audits, spare-part supply, and installation contracts with manufacturers.

Record keeping for a service enterprise: job cards, warranty register, spare inventory, invoice and GST records, and customer follow-up log.

Pricing for installation is usually per hectare or per plant, plus material cost; always quote a site-specific design, not a flat rate.

Electrical safety: earth the pump and controller, use RCCB/ELCB, keep control panels dry and locked, and never work on live circuits.

Chemical safety: wear gloves, goggles and mask when handling acids, chlorine and fertilizers; store chemicals separately, labelled, away from water sources.

Fertilizer injection needs a backflow preventer; never allow fertilizer or chemical solution to enter the source or public supply.

Trenching and pipe laying: call for utility location, keep trenches shored in loose soil, and barricade open trenches.

Environmental protection: avoid over-irrigation and nutrient leaching, dispose of filter backwash and chemical containers responsibly, and prevent soil salinity build-up.

Professional ethics: honest design and material specification, no overstating subsidy claims, confidentiality of farmer data, and clear warranty terms.

First aid: acid or fertilizer on skin → flush with plenty of water; eye splash → irrigate eyes for 15 minutes and seek medical help.