October is the month when the coming season’s pineapple plantings are decided, in southern Côte d’Ivoire as in the humid south of Cameroon. The field survey therefore happens now, not at the moment of ordering. Before a single pipe is chosen, you have to measure the flow available at the source in the driest month, the chemical quality of the water, the texture and infiltration rate of the soil, the slope and the head to overcome, then the quantity of planting material you can produce. A network sized without those figures works in the rainy season and runs out of flow exactly when the plant needs it.
Pineapple is a special case. According to table 12 of FAO publication 56, the plant closes its stomata during the day and opens them at night, so its transpiration is very low and most of the evapotranspiration comes from the soil rather than the foliage. The crop coefficients used are 0,50 in the initial phase, then 0,30 at mid season on bare soil and 0,50 with a grass cover, and 0,30 at the end of the cycle, for a plant height of 0,6 to 1,2 metre. These values assume soil covered 50 % by black plastic mulch with sprinkler irrigation, and FAO states that they fall by 0,10 under drip irrigation beneath plastic mulch. The water budget is therefore driven mainly by soil evaporation, which changes the way drippers are laid out.
Measure the source flow in the driest month
The technical sheet on Victoria pineapple published by CIRAD gives the starting benchmark: theoretical water requirements for pineapple are about 80 mm per month on bare soil. The same sheet translates that into practice, namely 10 to 15 mm per week on mulched soil and 20 to 25 mm per week on bare soil depending on the stage of the plant.
Those millimetres convert directly into a volume to pump. On one hectare, 80 mm per month is 800 cubic metres per month, close to 27 cubic metres per day. If the pump only runs 10 hours a day, you need a useful flow of about 2,7 cubic metres per hour for a single hectare, plus network losses. On bare soil in full heat, 25 mm per week calls for 250 cubic metres per week per hectare.
The survey therefore means measuring, not estimating:
- The borehole or well flow through a pumping test run at the end of the dry season, with the dynamic water level recorded during the test, not the flow quoted at commissioning.
- The static level and the drawdown, which give the real suction head.
- For a watercourse or a reservoir, the flow or volume at the lowest point of the year, reported by neighbouring farmers or measured with a timed bucket on a diversion.
- The storage volume you have, which lets you pump at a low flow for several hours and then irrigate at the network’s nominal flow.
CIRAD work on pineapple water nutrition identifies two moments when a deficit cannot be made up. During the rooting phase, one to two months after planting, soil moisture has to be maintained. During fruiting, irrigation has to be sustained and regular, slightly exceeding requirements to avoid irreversible damage. The same work indicates that maximum crop evapotranspiration, once the plant fully covers the ground, reaches about 74 % of the maximum measured evaporation. The method for sizing the pump itself is set out in our article on sizing a pump by flow and total head.
Have the water analysed, not just looked at
Clear water can be unusable, and cloudy water can be fine after filtration. The reference values are those of FAO bulletin 29 on water quality for agriculture, by Ayers and Westcot.
| Parameter | No restriction | Slight to moderate restriction | Severe restriction |
|---|---|---|---|
| Electrical conductivity | below 0,7 dS/m | 0,7 to 3,0 dS/m | above 3,0 dS/m |
| Total dissolved solids | below 450 mg/l | 450 to 2 000 mg/l | above 2 000 mg/l |
| Chloride, surface irrigation | below 4 meq/l | 4 to 10 meq/l | above 10 meq/l |
| Boron | below 0,7 mg/l | 0,7 to 3,0 mg/l | above 3,0 mg/l |
The sodium adsorption ratio is never read on its own: FAO always interprets it against the conductivity, because it is the combination of the two that decides the infiltration risk. A national soils laboratory or a university laboratory runs these analyses, and the results sheet belongs in the project file.
The choice of watering method partly follows from that analysis. The FAO manual on choosing an irrigation method notes that sediment laden water pushes you towards surface irrigation, to avoid clogging drippers and sprinklers, while drip irrigation is particularly suitable for saline water. On a borehole carrying sand, the survey therefore has to budget for the filtration station, which counts as a sizing component in its own right.
Identify soil texture and infiltration
The CIRAD sheet is clear on what the plant needs: a loose, homogeneous, well aerated and well drained medium, a pH of 4,5 to 5,5, a bed or ridge height of at least 25 cm, and rooting that generally does not exceed 35 cm in depth.
That last figure governs the whole irrigation schedule. The FAO training manual on irrigation water management gives an available water capacity of 25 to 100 mm per metre of soil for a sand, 100 to 175 mm per metre for a loam and 175 to 250 mm per metre for a clay. Over 35 cm of loam soil, the usable reserve is therefore only about 35 to 61 mm. A pineapple does not sit on a large reservoir: it needs frequent, moderate applications, which rules out long irrigation intervals.
The same manual sorts infiltration rates into three families: low below 15 mm per hour, medium from 15 to 50 mm per hour, high above 50 mm per hour. The manual on choosing a method adds the operational threshold: above 30 mm per hour you have to move to sprinkler or drip irrigation, because surface irrigation can no longer distribute the water. The test is done on site, with an infiltrometer or simply a cylinder pushed into the soil and the water level recorded every five minutes, at several points across the plot.
Record the slope and the head to overcome
Slope closes or opens options, and the FAO manual thresholds are numeric. Basin irrigation needs flat land, at 0,1 % slope or less. Furrow irrigation accepts flat to mildly sloping land up to 0,5 %, and contour furrows hold up to 3 %. Border irrigation works up to 2 % on sandy soil and up to 5 % on clay soil. Beyond that, or on uneven ground, FAO states that sprinkler and drip irrigation are preferable since they need little or no land levelling.
On a pineapple plot in rolling country, the useful survey is therefore a rough topographic one: high points and low points, the difference in level between the source and each block, the length of the laterals. That difference in level, added to the operating pressure of the drippers or sprinklers and to the friction losses, gives the total head the pump will have to work against. For a sprinkler system, spacing is derived from the wetted diameter and the wind, following the rule detailed in our article on sprinkler spacing.
Count the planting material in the same survey
A pineapple project stalls more often on suckers than on pipes. A technical sheet published in 2015 by CORAF and the CNRA of Côte d’Ivoire describes mass production of plantlets from harvested pineapple stems: the stems are split lengthwise, laid on a substrate and managed under a plastic tunnel between 25 and 30 °C at 80 to 90 % humidity. Axillary buds appear within two weeks, and plantlet harvest spreads over five months.
The figures in the sheet allow the area to be planned: one stem produces about ten plantlets on average over five months, with the H4 hybrid reaching 15 plantlets per stem and Smooth Cayenne around ten, and the technique covers the planting needs of at least 10 hectares from one hectare of mother plants. The best performing substrate in the trial combined coir fibre, coarse or ground to a powder, with peat. The properties of locally available substrates are compared in our article on choosing a soilless substrate, and the design rules for the tunnel itself in our file on agricultural greenhouses in tropical Africa.
On density, the CIRAD sheet on Victoria pineapple in La Réunion gives an order of magnitude to adapt: with 1,65 metre between bed centres, a three row layout holds 60 606 to 90 909 plants per hectare at a spacing of 0,30 to 0,20 metre along the row, and a four row layout 80 808 to 121 212 plants per hectare. These high densities belong to an intensively managed export crop, with fertilisation of 300 units of nitrogen and 450 units of potassium split into 7 applications for a target above 70 tonnes per hectare over the cycle. They serve as an upper bound rather than a general recommendation, and the density chosen on your plot has to account for the variety, the target market and the irrigation capacity established by the earlier measurements.
The survey to bring back from the field
| Data | How to record it | Benchmark |
|---|---|---|
| Source flow | Pumping test at the end of the dry season, dynamic level tracked | About 27 m³ per day per hectare to cover 80 mm per month |
| Water quality | Laboratory analysis, conductivity, dissolved solids, chloride, boron, sodium | Conductivity below 0,7 dS/m means no restriction |
| Soil texture | Auger samples at several points, feel test confirmed in the laboratory | Available water of 100 to 175 mm per metre for a loam |
| Infiltration | Cylinder pushed into the soil, level recorded every 5 minutes | Above 30 mm per hour, sprinkler or drip |
| Rooting depth | Observation of a profile on a neighbouring crop | Generally no more than 35 cm for pineapple |
| Soil pH | Soil analysis on a composite sample | 4,5 to 5,5 for pineapple |
| Slope and level difference | Rough topographic survey, high and low points, lateral lengths | Beyond 2 to 5 % depending on soil, sprinkler or drip |
| Planting material | Inventory of mother plants and of stems available after harvest | One hectare of mother plants for about 10 hectares to plant |
These eight lines form the base of a feasibility study. They fit on one sheet, they are collected in two days of fieldwork for a plot of a few hectares, and they prevent the most expensive outcome: a network bought off a drawing, installed, then starved of water. The context of the Ivorian sector is set out in our overview of agriculture in Côte d’Ivoire.
Building your project with JOGOO
JOGOO Agriculture carries out the field survey, the feasibility study and the full delivery of an irrigated scheme, from the borehole to the last dripper. See the Turnkey Agricultural Projects page for the approach, the Agricultural Consulting & Engineering page for agronomic support, and the Contact page to arrange a visit and receive a quote.
Frequently asked questions
What water volume should be planned per hectare of pineapple?
CIRAD gives theoretical requirements of about 80 mm per month on bare soil, that is 800 cubic metres per month per hectare, and a practical schedule of 10 to 15 mm per week on mulched soil against 20 to 25 mm per week on bare soil.
Why is the crop coefficient for pineapple so low?
Because the plant closes its stomata during the day, which sharply reduces its transpiration. FAO publication 56 gives 0,50 in the initial phase, 0,30 at mid season on bare soil and 0,30 at the end of the cycle, with most of the evapotranspiration coming from the soil.
At what infiltration rate should surface irrigation be dropped?
Above 30 mm per hour, according to the FAO manual on choosing an irrigation method, you have to move to sprinkler or drip irrigation.
What electrical conductivity makes water difficult to use?
FAO bulletin 29 puts the no restriction limit at 0,7 dS/m, the slight to moderate restriction band from 0,7 to 3,0 dS/m, and severe restriction above 3,0 dS/m.
How many plantlets can one pineapple stem produce?
About ten on average over five months according to the CORAF and CNRA sheet, with the H4 hybrid rising to 15 plantlets per stem and Smooth Cayenne staying around ten.
Why record the flow at the end of the dry season?
Because the flow available at the least favourable moment is what sizes the network. A borehole measured in the rainy season gives a figure the plot will not see again when the plant needs it most.
Sources
- CIRAD, COSAQ project, technical sheet, La culture de l’ananas Victoria à La Réunion pour l’exportation
- CIRAD, Fruits journal, volume 42 number 11, 1987, Nutrition minérale et hydrique de l’ananas
- FAO, Irrigation and Drainage Paper 56, Crop evapotranspiration, table 12 of crop coefficients
- FAO, Irrigation and Drainage Paper 29, Ayers and Westcot, Water quality for agriculture, table 1
- FAO, Irrigation Water Management, training manual, Soil and water
- FAO, Irrigation Water Management, Irrigation methods, choosing an irrigation method
- CORAF and CNRA Côte d’Ivoire, 2015 technical sheet, Comment produire en masse des vivoplants d’ananas
