IIGarden irrigation: Alternativetechniques and techonologydiffusion in dry regionsMonica Murata and Chris Lovell

A number of simple, low-cost irrigation techniques have beendeveloped that improve both yields and water use efficiency. Sowhy has the technology diffusion process had such a chequeredhistory among farmers in Zimbabwe's dryland areas?

1. Rutenberg, G. (1971). 'TrickleIrrigation literature Survey',Israel Centre of WaterworksAppliances Publications:International Expert Panel onIrrigation.

2. Anon. (1979). 'Kuzeh potirrigation'. Irrinews No. 11.3. Power, G. (1985). 'Porouspots help crops in north-eastBrazil' World Water, July pp.21-23.

The use of porous clay pipes forsub-surface irrigation datesback to 1896.

is]1uiii 'III

'"OJ186 I

Insemi-arid environments, water scarcityhas led to the search for irrigation

methods that use water efficiently.Development and assessment of water-saving irrigation techniques began at theLowveld Research Stations (LVRS) inZimbabwe in 1985. The objective was tocompare low-cost methods of irrigationthat improved water-use efficiency incommunity gardens by reducing loss ofwater evaporation from the soil. Methodstested included sub-surface irrigation(applying water beneath the soil surfacethrough either home-made clay pipes orporous clay pots), home-made dripirrigation (applying water to a limited areaof the soil surface) and improved floodirrigation (applying water beneath asurface mulch). Each method was found toimprove water-use efficiency (yield percubic metre of water used) - whencompared to traditional flood irrigation ofbare soil, but take-up by farmers inZimbabwe's communally manageddryland areas has been, in general,disappointing, for a number of importantreasons.

About the conceptsSub-surface irrigation by pipes dates backto 1896 when a German system known asKuchluhn used sub-surface concrete pipes,the upper part of which were porous. In1923, Kornev in Russia developed anirrigation network composed of porousclay pipes joined with rubber joints andburied at a depth of between 0.2 and 0.3mat intervals of 1m, the lines connected to acontainer placed at the highest point.Later research led to the use of clay pipeswhich were 27 per cent porous.! Pitcher

irrigation is traditional in the Punjab, inIran where it is called kuzeh pot irrigationand, more recently, has been used inSahelian Nigeria, Argentina, Brazil,Bolivia and Chile.2,3 Surface mulches areknown to reduce soil evaporation byincreasing the relatively non-turbulentlayer of air above the soil, and by offeringincreased resistance to water-vapour flowfrom the soil surface to the atmosphere.Various mulches ranging from organicresidues to polyethylene films andpetroleum emulsions have been used tomodify the hydrothermal regime to bettersuit the crop, and many studies haveshown that mulching can help in moistureconservation.

Technology developmentat LVRSSub-surface irrigationPorous clay pots or unglazed earthenwarepitchers, common to rural areas, come in arange of sizes and shapes. At LVRS, thepots have 0.08 to O.lm-long, 0.02 to 0.04m-diameter necks, with a capacity rangingfrom 0.5 to 2.5 litres. They provide asimple irrigation system. Staff bury thepots neck-deep in the soil next to plants,or between rows at intervals of 0.3m.When filled, water seeps from each pot viapores in the wall, forming a wetted zonesimilar to that formed by a sub-surfacedrip-irrigation source. The amount ofwater that can be applied is controlled bythe pot volume. Different irrigationregimes can be achieved by varying thefrequency of filling. Where available,gourds pierced with small holes offer analternative to the clay pots.

II1IIJm:D VOL.17 NO.2 OCTOBER 1998 23

irrigation and the small farmer

DisadvantagesAdvantagesIrrigation Method

Flood irrigation beneath three rows per bed, the third row beingmulch placed directly above the pipes; simpleAt LVRS, native grasses (Eragrostis sp. and mulches, particularly of manure, canHeteropogon sp.), maize stover, rice straw, improve germination and seedlingand neem tree leaves were used to provide establishment above clay pipes; and liquidsurface mulches during irrigation trials. fertilizer can be applied successfullyOther suitable materials include leaf-litter, through the pipes by first dissolvingcoarse sand, and even flat stones. manure (or inorganic fertilizer) in

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~irrigationwater~radayor~obefore irrigation.

Table 1. Advantages and disadvantages of simple micro-irrigation methods.

4. Batchelor, C.H., Lovell, C.J.and Murata, M. (1996). 'Simple

micro-irrigation techniques forimproving irrigation efficiency onvegetable gardens', AgriculturalWater Management, 32, 37-48.

5. Lovell, C.J., et al (1992).'Development of small-scaleirrigation using limitedgroundwater resources: ThirdInterim Report'. ReportoDN92/4 , Institute ofHydrology, Wallingford, UK.

6. Murata, M., et al (1995).'Development of small-scale

irrigation using limitedgroundwater resources: FourthInterim Report'. Report ODA95/5, Institute of Hydrology,Wallingford, UK. 104pp.

7. Murwira, K. (1995). 'Freedomto change: the Chiviexperience', Waterlines, Vol. 13,NO.4.

The research processOver eight years, LVRS conducted a greatnumber of replicated irrigation trials tomeasure and compare crop yields andwater-use efficiency with those oftraditional flood irrigation.4,5,6 The cropsincluded maize, tomatoes, rape, okra,cabbage, beans, carrots and onions. Someof the practical findings of the trials aresummarized in Table 1.

In general, gardeners did not haveproblems with pipe installation; one quickdemonstration was sufficient. But peopledid have reservations about whetherseedlings could extract water applied 0.1to 0.2m underground; how fertilizers(especially manure) should be applied;and whether only ~o rows of plants perbed could be grown with sub-surfaceirrigation instead of the three rowstraditionally grown on flood-irrigatedgardens. Studies found that sub-surfaceirrigation can be used successfully with

Not efficient in water use. No inherentcontrol against over-irrigation. Labourintensive.

Technology diffusionSadly, the technology-diffusionprocess, which started in about1990, has had a cheque redhistory. Initially, agriculturalextension staff were invited toLVRS to see the alternativeirrigation techniques. Despiteexpressions of interest made atthe field days, there was littleevidence of technology transferthrough these staff to localcommunities.In contrast, Intermediate

Technology (ITDG), which wasthen an NGO involved in aFood Security Project in ChiviDistrict, brought a group oflocal farmers to LVRS to see arange of research ideas. Thegroup - 90 per cent women,was particularly interested inthe idea of sub-surface

irrigation. As the women were alreadyskilled potters, they felt capable of makingtheir own pots and pipes. Pipe-makingdemonstrations were conducted atChiredzi and in Chivi. The womenexperimented with the system in 14 groupgardens, where they discovered that thetechnique reduced both the amount ofwatering required, and the time needed totend their gardens.?

In another initiative at this time, theurban community around a Kellog-fundedgarden in Chiredzi town were introducedto sub-surface irrigation by MrMharapara, a KILP fellow. Three projectmembers were trained to make pipes andthey in turn instructed others. Similarly,Hippo Valley, a local sugar estate,expressed interest in adopting the methodfor use by employees in their backyardgardens; other NGOs such as FriedrichEbert Stiftung introduced the method toestablish hedges and gardens in theirprojects; and agricultural extension staff

Cost and availability of materials. Degreeof management skill required. Waterfiltration required. No inherent controlagainst over-irrigation.

Initial skill and labour required formanufacture and installation. Less robustthan clay pipes. More labour-intensive:pots have to be filled individually. Porosityof pots decreases with time. Difficult tocope with heavy water requirements.

Potential for pest and disease increase.Material suitable for mulching not alwaysreadily available.

Initial labour and skill required for pipemanufacture and installation. Cropestablishment can be poor if initialirrigation only via pipes.

Traditional, well-known method. Easyto perform. Good crop establishment.Minimum additional inputs.

Improved water-use efficiency. Gooduniformity of wetting. Reduceddrudgery and effort of carrying water.

Improved water-use efficiency. Pipesmade locally. Robust method. Lowlabour requirement. Some inherentcontrol against over-irrigation. Gooduniformity of wetting. Low-cost, simple,easy to learn. Once installed, pipesgood for several years.

Improved water-use efficiency. Inherentcontrol against over-irrigation. Can bepositioned next to individual plants orin very small plots or undulating land.

Improved water-use efficiency. Lowskill requirements and easy to carryout. Good crop establishment. Protectsfruit from damp soil. Prevents soilcapping and reduces soil erosion.

Improved flood irrigation(mulch)

Traditional flood irrigation

Pitcher irrigation

Sub-surface pipe irrigation

Low-head drip irrigation

24 VOL.17 NO.2 OCTOBER 1998 IZIIIE

irrigation and the small farmer

Research at LVRSfound women to be particularly interested in sub-surfaceIrrigation; many are already skilled potters.

began promoting the ideas throughdemonstration plots at regional shows.

Why such low adoption?Despite much initial interest, uptake ofthe research has been disappointing.Although the alternative irrigationmethods are simple and low-cost,undoubtedly save water, and improveyields under research-station conditionssome five years later these methods are'not widely used. We have not been able toconduct an ex-post evaluation. This wouldbe a useful exercise and relevant to otheragricultural research projects. However,we can suggest why uptake of this researchhas been poor to date:• Research findings - in the form of

pamphlets, etc. written in the locallanguages have not been disseminatedadequately. Communities need accessto information about irrigationscheduling, crop rotations, marketingstrategies, and pest and disease control,if they are to derive the maximumbenefits from the new technologies.

• Inadequate opportunities for loca]communities to see new ideas, throughexposure visits and to learn by doing.Finding out via extension staff, or bybeing presented with results at researchstations is not ideal. Research andextension staff must help facilitatevisits and encourage local farmers tocarry out their own experiments basedon what they have seen.

• Very few demonstrations wereconducted with farmers under localconditions, so other factors, such asproduction aims, labour constraints,and access to materials, could not beconsidered properly during thedevelopment phase. Also, the LVRStrials were on a single soil type, a sandyclay loam, and insufficient attentionwas paid to planting arrangements thatcould conserve water and improve pestand disease control - a second keyconstraint facing local farmers.

• Improved water supply. The irrigationtrials and initial interest in water-savingcoincided with an unprecedented drycycle, culminating in the severe droughtof 1991-2. Since then, above-averagerainfall has replenished ground- andsurface-water supplies, so interest inwater-saving methods has declined -this interest should be reactivated when

the next dry cycle commences.8• Water in Zimbabwe's communally

managed dryland areas is a common-property resource. This, combined witha poor local understanding ofgroundwater behaviour, places seriouslimitations on both the incentive andresponsibility felt by individuals toconserve the resource.9

• Finally, from the woman farmers'perspective, the benefit or advantagesof these improved irrigation techniquesdo not outweigh the disadvantages.Water-resource management and the

uptake of water-saving irrigation methodsin communally managed dryland areas iscomplex, relying on a mix of physical,social and economic factors. As Lovelldescribes on page 5 of this issue, recentwork in Zimbabwe has highlighted themany benefits of productive groundwaterdevelopment. The big question remains:can the income generated from productivewaterpoints provide the incentive forcommunity-based actions that contributeto improved water-use efficiency andresource management at the catchmentscale? Farmer-participatory research hasan important role to play, but will notalways be easy. Experience to date showsthat it will depend on farmers gainingimproved access to information, and onthe willingness of researchers, extensionstaff and farmers to learn together. •

8. Moriarty, P.B.andLovell, C.J. (1988).'Groundwater resourcedevelopment in thecontext of farmingsystems intensificationand Changing rainfallregimes: a case studyfrom south-eastZimbabwe'. AgRENNetwork Paper 81,001.London.

9. Waughray. O.K., et al(1997). 'Communityresource managementand livelihood strategies'.Final Reporlto OOA.Report 97/1, Institute ofHydrology, Wallingford,UK.

AcknowledgementsThe authors would like to thankthose who gave support andadvice during the researchendeavours and duringpreparation of this manuscript.Financial support for part of theresearch described wasprovided by the DFIDEngineering Division, London.

about the authorsMonica Murata works at the

Agronomy Institute, Box CY550,Causeway, Harare, Zimbabwe.

Dr Chris Lovell is a PrincipalScientific Officer with the. Institute of Hydrology,

Wallingford, Oxfordshire, UK.

IIIIIIIm:D VOL.17 NO.2 OCTOBER 1998 25

irrigation and the small farmer

How to make clay pipes

• With your hands, crush what should be reasonably heavy clay soil; leave it to soak overnight until pliable.Remove stones and roots and mix the clay 'paste' thoroughly by throwing It repeatedly against a hard surface• Place a rectangular wooden frame, with an internal length, width and depth of 0 3.0.25 and 0.016mrespectively, on a sheet of plastic of the same size. and fill completely with soil paste. Take care to removetrapped air. Level the clay uSing a straight edge (pulled along the sides of the frame). and make it smooth bysprinkling water at the same lime• At either end. form grooves allOWing a Joint of constant wall thickness to be formed when the sheet of clay ISwrapped around a 0 36m-long O.073m-wide wooden rolling pin. Form a strong joint by kneading the two ends ofthe clay sheet together, and Insert the rolling pin plus clay into an outer mould. constructed of a 0.25m length of'125mm'-diameter PVC pipe cut along one side, with simple handles attached to allow the pipe to be openedslightly to accept the rOiling pin and clay• Close the PVC pipe by squeezing the handles together, rotating the rolling pin several times so that the pipehas a smooth inner surface Similarly, smooth the outer surface (by rotating the outer mould) and remove excessclay With a knife Then remove the wooden cylinder and place the outer mould plus clay end-up on the ground.Remove the outer mould and plastiC sheet and there ISyour finished five-minute clay pipe.• It is important to maintain slow uniform drying of the pipes before firing. After moulding. stand the wet claypipes on end for three to four hours In the open shade. Lay them side by side for two days - rolling themoccasionally - and, finally. place them in direct sunlight for a day before putting them in a shallow. bark-filled pit.The pit should hold approximately 50 pipeS per firing. Place a layer of tree bark on the bottom, followed by thepipes. tilted at a slight angle Place bark inside each pipe, and over the pipes. Light the fire and allow it to bumovernight until only ashes remain. The pipes are ready for use as soon as they have cooled down.

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The finished pipe should be O.24m long, With an inner diameter of 0.075m and outer diameter of 0 115m. Placethem along the centre line of garden-beds, laid end to end in a level trench; then backfill With 0.1 to 0 2m of soilabove the pipes depending on the soil type and crop to be grown. So thatthey fill with water. form an inlet at one end by tilting the first pipe section,having angled the lower end dUring manufacture to join smoothly With thesecond, level pipe. At the other end of the bed, normally 3 to 6m long.block the pipe with a large stone To irrigate, pour water into the pipe. eitherfrom a bucket or hose-pipe, this Will seep directly into the root zone via thejOints between pipe sections.• Where available perforated-bamboo or PVC pipes offer an allernahve \0 clay pIpes.

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26 VOL.17 NO.2 OCTOBER 1998 II11'I!D