Crop irrigation · Long-cycle vegetable
Drip Irrigation for French Beans
French beans (green beans, French beans) are a long, multi-harvest crop: 2.5–4 months to first pick, then weekly harvests for months. Its irrigation need is the steady middle one — consistent moisture through every picking wave, with the supply that keeps the picking coming through the dry spells.
French bean's irrigation requirements
French beans are a moderate water user with a long window — more demand per week than kale, less than cucumber, and a harvest rhythm that keeps the demand going for months. The crop's sensitivities are the usual two: dry spells during flowering and pod set (fewer pods, smaller pods, and the plant shuts its production down for the dry weeks), and waterlogging in wet seasons (root rots, especially on the heavier soils). Drip's pattern — moderate, frequent, even — is the standard for the crop, and its two-line-per-bed setup is the same workhorse specification as the other row vegetables.
French beans are grown across the highlands and the Rift (Nyeri, Kirinyaga, Murang'a, Nakuru, Kericho, the Meru highlands) and increasingly in the midlands for the dry-season market — a crop where the drip system is what lets the picking calendar run on time instead of on rain.
The system setup
| Parameter | Typical specification | Why |
|---|---|---|
| Plant spacing | ~30cm in-row (bush varieties), 45–60cm on pole/running types, rows/beds 0.9–1.2m | Bush vs running type changes the emitter spacing |
| Lines per bed | 2 (bush on standard beds); 1–2 on running-type layouts | Full-bed coverage for the long picking season |
| Emitter spacing | 20–30cm on drip lines | Half to three-quarters of the in-row spacing |
| Emitter flow | 1.6–2.7 L/h | Short frequent runs suit the bean's demand rhythm |
| Line type | Multi-season line (the picking season is long enough to justify it) | Tape is viable for a single fast season |
| Fertigation | Light program or none — base feeding plus a short top-dress is common; fertigation on long commercial blocks | The crop's feed bill is modest compared to tomato/cucumber |
Filtration and water source
The long picking season is the filtration story: a bean block that runs for four months of weekly harvests is a four-month test of the filter routine — weekly cleaning for surface water, line-end flushing on schedule, and the pressure-drop watch where gauges are fitted. The source logic is standard: disc for borehole, sand/media + disc for dam or river. The filtration guide has the details.
Scheduling through the picking waves
- Establishment: frequent light runs; beans set in quickly and the early weeks are easy.
- Flowering → first pods: steady moderate supply — the pod-set window is where dry spells show up as lost production for the whole wave.
- Picking season (the main event): moderate frequent runs for months. The rhythm matters more than the volume: the crop picks weekly, and the supply should be the thing that never changes.
- Wet-season operation (highlands): supplement, don't replace — the soil check before every run, and the schedule flexed with the rains. Root rot in a bean field is usually an over-watering story, not an under-watering one.
- End of season: the supply continues to the last planned pick; the block is turned and the lines rolled.
Common installation mistakes
- Emitter spacing wider than the bush planting — at 30cm in-row, a 40cm emitter is at the edge of acceptable; 20–30cm is the safe spec, and it's what keeps the pod rows even.
- One line per 1.2m bed on a 4-month picking season — the bed centre dries in the hot spells, and the inner-row plants lag through the whole season.
- Wet-season over-irrigation on a fixed schedule — the same highland story as cabbage: the schedule must flex with the rain, or the soil check takes over.
- Flush points skipped on a long-running fine system — the picking season is long enough for sediment to settle, and the end rows of the bed show it in the final harvests.
Cost considerations
French beans sit in the mid vegetable band: two lines per bed, standard emitters, fertigation optional. The dry-season value of beans in the midlands is what makes the system pay there — the market pays a premium for off-season produce, and drip is what produces it. See the cost guide for the market ranges.
Related reading
FAQ
French bean drip questions
How often should french beans be irrigated?
Every 1–2 days with moderate runs in the dry season, daily on sandy soil in the hot spells, and less in the rains (supplement, don't replace). Through the picking season the rhythm is the point — the crop picks weekly, and the supply shouldn't vary with the week.
How many drip lines per bed for beans?
Two per bed is the standard for 0.9–1.2m beds with 20–30cm emitter spacing (bush varieties at ~30cm in-row). Running-type beans on wider layouts can run one or two lines depending on the bed width — the design confirms from your layout.
Why does my bean production stop in the dry season?
Beans are one of the crops that shut their production down under water stress during flowering and pod set — the plants survive the dry weeks, but the pods don't come. If the supply lightened in the dry spells, that's the cause. The fix is the schedule holding steady through the pod-set windows, which is exactly what a timer or controller is for.
Do french beans need fertigation?
Not necessarily — base feeding plus a short top-dressing program is common and works well. On long commercial blocks, a light fertigation program improves the later waves, which is where the soil feed runs out. The fertigation guide covers the setup if you go that way.
Where do you install bean systems?
Highlands and Rift — Nyeri, Kirinyaga, Murang'a, Nakuru, Kericho, Meru — plus the midland dry-season blocks. See the locations page; send your layout for a quote.
Bean season on the calendar?
Send your bed layout and water source — we'll spec the lines and the schedule that keeps the picking coming.