Farkesht technical guide
Irrigation methods, and choosing correctly between them
The gap between the worst method and the best one is half the field’s water. This dossier puts the five families side by side: where the water goes, what pressure each needs, which conditions each suits, and how any of them has to be scheduled.
- Efficiency gap, worst to best method
- 50%
- Typical drip head pressure
- 1.5bar
- Minimum filtration for drip
- 120mesh
Updated August 20, 2026Farin Kesht Taban Co.
Five families
The shape of the water in the soil is the real difference
An efficiency table tells you drip beats flood. It does not tell you why. Each method’s wetting pattern does.
- Root depth40–60 %
Surface and flood
Basin, border and furrow. Almost no capital cost, but most of the water passes below the roots.
- Root depth65–85 %
Sprinkler
Solid set, wheel-move or centre pivot. Even coverage, but part of the water evaporates or drifts before it lands.
- Root depth75–85 %
Micro-irrigation
Micro-sprinklers and bubblers under the canopy. For orchards and sandy soils, where a single emitter wets too little.
- Root depth85–95 %
Surface drip
Laterals on the surface with emitters. A contained wetted bulb per plant: least wetted area, least weed pressure.
- Root depth90–95 %
Subsurface drip
Laterals buried in the root zone. The surface stays dry, so evaporation nearly disappears — given the right filtration and flushing.
| Method | Application efficiency | Operating pressure | Capital cost |
|---|---|---|---|
| Surface and flood | 40–60 % | 0–0.3 bar | 1 of 4 |
| Sprinkler | 65–85 % | 2.5–4.5 bar | 2 of 4 |
| Micro-irrigation | 75–85 % | 1.5–2.5 bar | 3 of 4 |
| Surface drip | 85–95 % | 1–2.5 bar | 3 of 4 |
| Subsurface drip | 90–95 % | 1–2.5 bar | 4 of 4 |
These efficiencies are ranges, not verdicts. A drip system at the wrong pressure with no filter can perform worse than a well-levelled flood field: a good method installed badly is a bad method.
Water audit
Of every 100 litres, how much reaches the crop?
The losses are not interchangeable and neither are their remedies: evaporation is a scheduling and nozzle question, deep percolation is a run-length and soil question, runoff is a levelling question.
- Surface and flood50 %50 %Reaches the crop: 50 %Evaporation and drift: 10 %30 %Deep percolation: 30 %Runoff: 10 %
- Sprinkler75 %75 %Reaches the crop: 75 %18 %Evaporation and drift: 18 %Deep percolation: 5 %Runoff: 2 %
- Micro-irrigation80 %80 %Reaches the crop: 80 %12 %Evaporation and drift: 12 %Deep percolation: 6 %Runoff: 2 %
- Surface drip90 %90 %Reaches the crop: 90 %Evaporation and drift: 4 %Deep percolation: 5 %Runoff: 1 %
- Subsurface drip93 %93 %Reaches the crop: 93 %Evaporation and drift: 1 %Deep percolation: 5 %Runoff: 1 %
- Reaches the crop
- Evaporation and drift
- Deep percolation
- Runoff
Hydraulic design
Four numbers that make or break a design
Two systems built from identical pipe and identical emitters can deliver completely different efficiency. The difference is these four figures.
- 90%
- Emission uniformity (EU)
- 20%
- Allowable pressure variation
- 2%
- Maximum lateral fall
- 8h
- Maximum block run time
The minimum a new drip block should return on a field test.
Spread across one block; beyond this, uniformity starts to fall away.
Past this slope, pressure-compensating emitters stop being optional.
The basis of blocking: source flow divided by block demand sets how many blocks there are.
No design is drawn before the source flow and pressure are measured. Most failing systems we are called to have the right pipe and the wrong source.
Selection
Which method for which conditions
Method selection does not start with the crop, it starts with the constraint: the slope, the water quality, how much water there is, and the soil texture.
| Suitability matrix: field condition against irrigation method | Surface | Sprinkler | Micro | Drip | Subsurface |
|---|---|---|---|---|---|
| Steep ground | Not recommended | Suitable | Suitable | Suitable | Suitable |
| Saline water | Not recommended | Not recommended | Not recommended | Suitable | Suitable |
| Scarce or rotational water | Not recommended | Not recommended | Suitable | Suitable | Suitable |
| Sandy soil | Not recommended | Not recommended | Suitable | Suitable | Suitable |
| Strong wind | Suitable | Not recommended | Not recommended | Suitable | Suitable |
| Row crops | Suitable | Suitable | Not recommended | Suitable | Suitable |
| Orchards | Suitable | Not recommended | Suitable | Suitable | Not recommended |
The table shows technical suitability, not the best option. Drip suits saline water because it keeps salt off the leaves — but that same water still needs its own leaching schedule.
Scheduling
When to irrigate, and how much
The best system in the world is wasted on a calendar schedule. Soil water is spent at a rate the weather sets, and it is put back just before the allowable depletion line is crossed.
- Field capacity
- Allowable depletion
- Stress zone
- Irrigation event
Crop water demand
ETc = ET₀ × Kc
Reference evapotranspiration multiplied by the crop coefficient for that growth stage. The output is millimetres used per day.
Depth and interval
d = (θfc − θ) × Zr ÷ Ea
The deficit back to field capacity, times rooting depth, divided by system efficiency. The output is the net depth per event.
Water quality
What actually blocks an emitter
Emitter clogging almost always has one of three causes: suspended particles, chemical precipitation, or biological growth. The bands below are the range in which the hazard is low.
Suspended solids
0–50 mg/L
0200 mg/L
Sand and silt particles; removed by mechanical filtration.
Total dissolved solids
0–500 mg/L
02,000 mg/L
What later precipitates as carbonate and sulphate scale.
Water pH
5.5–7 pH
09 pH
Above 7.5 the likelihood of calcium precipitation rises sharply.
Iron
0–0.1 mg/L
01.5 mg/L
Oxidises into orange scale and feeds bacterial slime.
Manganese
0–0.1 mg/L
01.5 mg/L
Like iron, but a black deposit and harder to shift.
Bacterial population
0–10,000 /mL
050,000 /mL
Biological slime; controlled by periodic chlorination.
Filtration a drip system needs
The working rule: the filter must stop anything larger than a tenth of the emitter passage.
Screen filter
120 mesh≈ 130 µm
Cheap and simple; suits well water carrying mineral particles.
Disc filter
130 mesh≈ 120 µm
Higher holding capacity; for water with a moderate organic load.
Media filter
200 mesh≈ 75 µm
For surface water, reservoirs and algae, with backflushing.
No filter replaces flushing the lateral ends. A scheduled flushing routine, with acid or chlorine injection, is part of the design — not an emergency measure.
Questions
What growers ask about choosing a system
The six that come up most.
Which irrigation method is best?
That is the wrong question. The method follows your constraint: with scarce water and sandy soil, drip; with levelled ground and plentiful cheap water, improved surface can be the better economics. Establish the constraint first, then the method.
Is drip always worth it?
Where water is limited or expensive, almost always. But the real cost of drip is not the pipe: the filter station, the fertigation injection and the flushing routine are part of the system, and leaving them out blocks it within two seasons.
Which method suits saline water?
Drip or subsurface drip, because salt never lands on the leaf and continuous moisture keeps the concentration down in the root zone. In exchange, salt accumulates at the edge of the wetted bulb and you need periodic leaching.
Why do our emitters keep blocking?
Three common causes: the wrong filter or an unwashed one, chemical precipitation in high-pH water, and bacterial growth. A water analysis says which — without it, replacing emitters only postpones the problem.
Can an existing flood system be converted to drip?
Yes, but conversion does not start with buying pipe. Source flow and pressure are measured first, then the blocking is designed; in most cases the existing source cannot irrigate the whole area at once and the system has to be laid out in shifts.
How do I know how much water I am applying?
A meter at the head and a simple emitter discharge test. Until the delivered volume is measured, any discussion of efficiency is guesswork.
Want to know which method will actually work on your land?
We start with a water analysis and a measurement of the source flow. After that, choosing the method is the easy part.