development of an nft system of soilless culture for the tropics

Pertanika 8(1), 135-144 (1985)

Development of an NFT System of Soilless Culturefor the Tropics

E.S. LIMDepartment of Agronomy and Horticulture,

Faculty of Agriculture,Universiti Pertanian Malaysia,Serdang, Selangor, Malaysia.

Key words? Hydroponics; NFT; vegetables.

ABSTRAK

Penciptaan satu sistem pengeluaran tanaman tanpa tanah yang berdasarkan Teknik NutrientFilm (NFT) telah dikaji. Jenis longkang politin yang digunakan untuk NFT di rantau-rantau iklimsederhana didapati tidak sesuai untuk iklim tropika panas. Satu rekaan palung tohor yang meng-gunakan penebat haba didapati berkesan untuk mengawal peningkatan haba dalam zon akar.Tanaman-tanaman muskmelon, sayur-sayuran dan pokok-pokok hiasan telah ditanam dengan ber-

jayanya dengan sistem palung NFT yang diciptakan int. Sistem ini adalah murah, berekonomi, men-jimatkan tenaga buruh dan berkegunaan serbaguna.

ABSTRACT

The development of a soilless crop culture system based upon the Nutrient Film Technique(NFT) was studied. The conventional polythene gullies used for the NFT in temperate regions were

found not suitable for the hot tropical-climate. An insulated NFT shallow trough design was effectivein controlling heat build up in the root zone. Muskmelon, vegetables and ornamental plants were suc-cessfully grown with the NFT trough system designed. This system is cheap, economical, labour savingand versatile.

INTRODUCTION

In the soilless production of crops, varioussystems have been developed. These range fromthe fairly simple sand culture systems to theelaborate and expensive large-scale commercialsystems (Gericke, 1940; Harris, 1970; SholtoDouglas, 1976; Lim, 1982). The large-scalesystems have mainly been developed overseas foruse within glasshouses in cool temperate climaticzones.

Universiti Pertanian Malaysia (UPM) hassuccessfully set up a large-scale system for theproduction of various fruit and leaf vegetables(Lim and Wan, 1984). This system, theH-system, involves the use of a large volume of

nutrient solution circulated in troughs contain-ing the plants. The adaptation from the coolertemperate environment to the hot local condi-tion was provided by the large volume ofnutrient solution circulated and the use of cool-ing equipment. In Europe and other temperateregions, a system that has found wide applica-tion employs the nutrient film technique (NFT)which supplies the nutrient solution to the plantroots in a low volume (Cooper, 1982). Thissystem, besides using less nutrient solution, isalso simple to build and relatively inexpensive.In this study, the principle of the NFT wasapplied to the designing of a soilless cultivationsystem for use under local conditions. The newsystem that was designed was also evaluated foruse in the production of various crops.

E.S. LIM

MATERIALS AND METHODS

A study was initially set up to determine theeffect of various system designs on the root zonetemperature. Following this, the cultivation ofvarious crops was carried out. In one study, theproduction of muskmelon (Cucumis melo L.)was compared between the newly designed NFTtrough system and the H-system. In anotherstudy the production of lettuce was comparedbetween two versions of the NFT trough designand normal cultivation using soil. The cultiva-tion of various vegetables and ornamental plantswas also studied using the NFT troughs.

In the study of root zone temperature,several designs of T:he growing units were com-pared. These units consisted of the conventionalpolythene gullies and specially designed, shallowinsulated NFT troughs. The polythene gullieswere made of 0.125 mm thick black polythenesheets folded into a triangular tent, 25 cm wideat the base, 30 cm high at the apex, 100 cm longand closed at the solution inlet end. Polythenegullies with external surfaces of black or whitewere compared. The NFT trough were con-structed from 2.5 cm thick polystyrene boardsand were 25 cm wide by 100 cm long. Poly-styrene trough covers with a reflective whitepolystyrene surface were provided. An internalair space of 2.5 cm height was provided betweenthe cover and the bottom of the trough. Each ofthese growing units received a continuous film ofwater flowing from one end down to the otherthroughout the period of measurement. Themaximum and minimum daily temperatureswere recorded for a period of 10 days.

In the second study the production of musk-melon was compared between the non- reflectiveinsulated NFT troughs described above and theH-system. A replica of the H-system was con-structed and consisted of a deep trough in whichnutrient solution up to a depth of 6.5 cm wascirculated. In the NFT troughs, seeds wereplanted in 5 cm rockwool cubes while in theH-system they were shown directly on to 2 cmgravel chips contained in small lattice basketssuspended in the nutrient solution. Plants werespaced 50 cm apart in both systems. Holes of 5

cm square were made in the polystyrene covers toinsert the rockwool cubes or to suspend thelattice baskets.

In another study the production of lettuce(Lactuca satiua LJ using 2 types of NFT troughdesigns were compared to that grown on a soilmixture made up of 3 parts loam and 1 partsand. The NFT troughs compared consisted ofthe earlier designed trough with an air-space of2.5 cm between the cover and the bottom and aredesigned trough in which the cover was placedflush the bottom of the trough over the film ofnutrient solution (no air-space). The lettuceplants were spaced in a triangular arrangement20 cm apart. The lettuce grown in the soil mix-ture was watered at least twice daily with thesame nutrient solution used for the NFTtroughs. The plants were harvested 40 days aftersowing.

Using the non-reflective NFT troughs,various other vegetables and an ornamental weregrown experimentally. These included fruitvegetables such as long beans (Vigna sesquipe-dalis L..), Chinese kale (Brassica alboglabra h.)mustard greens (B. chinensis L., B. rapa L., B.juncea L.), lowland cabbage (B. oleracea var.capitata L.), cucumber {Cucumis sativus L.),hot pepper (Capsicum frutescens h.)t and mari-gold (Tagetes species).

RESULTS

Root Zone Temperature

The polythene gullies were found to absorba large amount of heat particularly when theywere exposed directly to the sun. During the daythe temperature within the polythene gullies roseup to a recorded maximum of 54°C. The tempe-rature within the polythene gullies wasinfluenced by the colour of the external surface.The black polythene gully was significantlyhotter inside than the white surface polythenegully (Table 1). The polystyrene NFT troughswere significantly cooler than the two types ofpolythene gullies. The NFT trough with a reflec-tive top was also significantly warmer than thetrough with the non-reflective white top. Nodifference was found in the temperature within

136 PERTANIKA VOL. 8 NO. 1, 1985

DEVELOPMENT OF AN NFT SYSTEM OF SOILLESS CULTURE FOR THE TROPICS

the NFT trough with the non-reflective white topand the outside maximum air temperature.

The minimum night temperatures of allpolythene gullies and the polystyrene NFTtroughs were significantly lower than the mini-mum air temperature. The coolest growing unitwas that of the NFT trough with the non-reflec-tive white top.

Muskmelon Experiment

The muskmelon plants grown in the poly-styrene NFT troughs grew normally and borefruits (Plate 1). The growth rate of the plants as

indicated by the number of opened leaves after 6weeks were rio different from that grown in theH-systems. The development rate of the fruitswas also similar (Table 2). The mean fruitweights were 1.20 kg for the NFT trough and1.07 kg for the H-system. However, the diffe-rence was not significant. The brix measure-ments for the fruits were similar for both thesystems and averaged about 13 percent.Although no difference was evident in the pro-ductive capacities of the NFT trough system andthe H-system, it was observed that the stems ofthe muskmelon grown in the H-system becamebrown and dry from the collar upwards toward

TABLE 1Maximum and minimum temperature within various NFT growing units

Type of NFT growing units Temperature (deg. C)

Maximum Minimum

Black polythene gully

White polythene gully

Reflective polystyrene trough

Non-reflective polystrene trough

External shade air temperature

L.S.D. (P=0.05)

49.5

40.4

37.9

35.6

35.9

1.71

24.0

23.2

24.5

23.1

25.8

0.92

TABLE 2Comparison between muskmelon grown in the

H-system and the NFT trough system

Character measured H system NFT trough t statistic

Leaf number

Fruit circumference (cm)

Week 2

WeekS

Week 4

Week 5

Week 6 (harvest)

Fruit flesh thickness (cm)

Fruit weight (kg)

Brix (%)

26.2

20.7

30.7

36.1

38.8

41.3

3.35

1.07

13.1

27.3 0.740 ns

24.0

32.8

37.0

39.4

42.4

3.33

1.20

13.2

0.959 ns

1.121 ns

0.533 ns

0.300 ns

0.598 ns

0.078 ns

1.016 ns

0.128 ns

ns = not significantly different at P = 0.05.

PERTANIKA VOL. 8 NO. 1, 1985137

E.S. LIM

Plate 1

fruit maturation (Plate 2). The stems of themuskmelon plants grown in the NFT troughsremained a healthy green.

Lettuce Experiment

The lettuce crop was harvested 42 days aftersowing. The NFT troughs produced superioryields compared to those grown on soil (Table 3),The soil grown lettuce were very slow in theirgrowth right from the seedling stage and werestill relatively small compared to the lettuceplants grown in the NFT troughs at harvest(Plate 3). There was no difference found be-tween the two types of NFT troughs. The pre-sence or absence of an air-space above the rootmat did not significantly influence the yield.

Vegetable Production

The vegetables grown using the insulatedNFT troughs are given in Table 4. In all cases thegrowth of the vegetables was very rapid after theinitial seedling stage. All these vegetables were

APlate 2A



Mean plant

Cultivation method

NFT trough,

NFT trough,

Soil mixture

raised cover

flush cover

weightTABLE 3

of lettuce produced

Fresh

from NFT

weight (g)

264.8

294.4

12.92

troughs and soil

S.

45

42

3

E.

.32

.90

.12

§

Plate 3

TABLE 4Production of vegetables using the NFT trough system

Vegetable Trough area(sq. m.)

Days fromsowing

Yield(kg)

Chinese kale

Mustard greens:

B. chinensis

JB. juncea

B. rapa

Lettuce

Cabbage (head)

Cucumber

Long bean

Hot pepper

0.5 40 3.81

0.5

0.5

0.5

1.0

0.5(10 plants)

0.5(6 plants)

0.5(10 plants)

0.5( 6 plants)

40

45

25

45

40

40-55

45-70

60-90

2.90

6.14

1.97

10.11

6.42

3.72

2.55

2.50

PERTANIKA VOL. 8 NO. 1, 1985 139

E.S. LIM

to 45 days after sowing. The mustard green, B.rapa was earliest. It began flowering 25 dayssuccessfully grown to maturity using the NFTtrough system (Plates 4 and 5). Many of the leafyvegetables were ready for harvesting between 40after sowing and had to be harvested. Among

the leafy vegetables grown, the high yielderswere the mustard, B. juncea and lettuce. Thecabbage grew vigorously producing compactheads up to 1.15 kg after 40 days. The fruitvegetables also grew rapidly.

Plate 4A

B

Plate 4B

Plate 4C Plate 4D

Plate 4E Plate 4F



Plate 5A Plate SB

Ornamental

The NFT trough was also suitable for grow-ing ornamental plants. Marigold plants took 45days from seeding to the first bloom. The flower-ing period was extended and continued over onemonth (Plate 6). Due to the size of the plantssome plant support was necessary.

Labour Requirements

In the cultivation of the various crops, theNFT troughs were found to be easy to use andrequired very little labour to plant, maintainand clean for reuse. Seeding was very rapid asthe seeds were sown directly on to the rockwoolwith the help of a pair of forceps. Dependingupon the crop, sowing a trough of one meterlong only required less than 5 minutes. Main-tenance consisted of nutrient replenishment and

PERTANIKA VOL. 8 NO. 1, 1985 141

E.S. LIM

TABLE 5Estimated cost of materials for the constructionof an NFT trough system for 100 sq. m area

Plate 6

pH control of the nutrient solution and thenormal activities such as the provision of plantsupports, pruning or pollination as required bythe particular crop. After harvesting, the clean-ing up of the NFT troughs was very rapidlycarried out. It was only necessary to remove thepolystyrene covers and roll up the root mat fordisposal. The troughs remained clean and couldbe used for planting another crop immediately(Plate 7). Reseeding of a new crop merely con-sisted of replacing the polystyrene cover, insert-ing fresh rockwool cubes and planting the seed.In the studies, no sterilization of the system wascarried out and the various crops grown did notsuffer any adverse effect.

Construction Costs

The cost of constructing the NFT troughsystem is low when compared to the various com-mercial systems available locally and abroad. All

Material

Polystyrene NFT troughs

Piping, tubing, etc.

Pump and electrical parts

Nutrient solution tank

Total

Amount ($)

450

150

200

150

950

Plate 7

the materials used for construction were readilyavailable locally. The actual cost would dependon the design and layout of the system. For anarrangement given in Fig. 1 the cost for the basicset up for an area of 100 square meters is esti-mated to be about $950 ringgit excluding instal-lation expenses (Table 5).

DISCUSSION

In the production of crops using the soillesscultivation method, the provision of optimumconditions to the root system of the plants is veryimportant. As most soilless production units arelocated above the ground, they are directlyexposed to solar radiation particularly when theplants are still small. This can lead to the rapidincrease of temperature within the growingunits. For most crops the optimum root zonetemperature is*between 25 to 30°C (Cooper,1982). Therefore, the maintenance of the rootzone temperature as close as possible to the opti-mum is necessary.

The study has shown that the polytheneNFT gullies that are being widely used in tem-perate soilless crop production system are notsuitable for use in the tropics. The high daytimetemperatures within them are well beyond theoptimum root zone temperature for crop pro-duction. Although the white coloured polythenegully is cooler than the black polythene gully byabout 10°C, the average maximum temperatureof 40°C is still too high for seedling establish-ment and good plant growth. Under local con-



ditions where a high intensity of solar radiation isexperienced, the simple polythene gully wouldnot be suitable. The use of polystyrene boards inthe construction of NFT planting troughs hassuccessfully reduced the heat build up. Theplain white polystyrene trough was the most ef-fective in preventing heat build up within theroot zone. With this type of growing unit, theroot zone temperature was the same as the shadeair temperature. No further benefit was derivedfrom having a reflective surface for the poly-styrene NFT troughs. In fact, due to the heatingup of the reflective layer, the temperature withinthe trough was slightly elevated above that of theair temperature.

The production of various crops was suc-cessfully carried out using the polystyrene NFTtroughs. Although the maximum temperaturerecorded for these troughs was about 35°Cbefore planting, there was no apparent deteri-mental effect on the seedling establishment aswell as later plant growth. This was evident forthe yields obtained in the various studies. Thecontinuous flow of the nutrient solution filmcould have provided some localised coolingeffect as the temperature of the nutrient solutionin the storage tanks was not more than 30°Cduring the day. Further reduction in the tempe-rature could have resulted from evaporativecooling around the rockwool cubes and thesurface of the solution film. In addition, duringthe latter stages of crop growth the plants them-selves provided ample shade over the NFTtroughs. With leafy vegetable, the entire troughwas covered by the leaves when the plants grewup.

The production of muskmelon by theH-system at UPM has been very successful (Urnand Wan, 1984). The NFT troughs that weredesigned were found to produce equally wellwhen compared to the H-system. Although themuskmelon crops were similar with both systems,there was some indication of healthier plantswith the NFT trough system. The rotting anddrying up of the basal portion of the stems wereonly found on plants grown in the H-system. It ispossible that the deep solution of the H-system

may have reduced the oxygen supply to the rootsthus affecting the health of the basal portion ofthe plants. In the NFT troughs the thin film ofsolution and the air-space provided allowed formaximum gaseous interchange relative to thevolume of solution present, thus providingadequate oxygen supply for healthy root andstem development.

The production of vegetables with the NFTtroughs is easily carried out. When compared tothe conventional growing method using soil, thesoilless NFT trough system proved to besuperior. Yields of lettuce grown on soil and inthe NFf troughs differed greatly even thoughthe soil grown crop was given the same nutrientsolution daily. Apparently the soil was unable toprovide optimum conditions for the root systemand good plant growth. With the NFT troughsthere were no restrictions on the development ofthe plant roots and since the nutrient film wasalways present, the plants sufferred no moistureor nutrient deficits.

The NFT troughs can be easily modified forthe growing of various crops. When changingfrom one crop to another it is only necessary tomodify the location of the planting holes in thecover. In the experiment, multiple-hole coverswere used. When planting a particular crop,rockwool cubes were inserted in the holes thataproximate the desired planting distance. Theextra holes that were not required were pluggedup with a piece of polystyrene. The same troughscould therefore, be used over and over again formany types of crops ranging from muskmelon toleafy vegetables and ornamentals. In contrast,the H-system required different plant containerswhen changing from crops such as the fruitingvegetables to the leafy vegetables. In addition,the H-system also required gravel of a smallersize for the leafy vegetables. All these modifica-tions were not necessary with the NFT troughsystem, thus further reducing costs.

The various cropping studies carried outhas shown the labour-saving potential of theNFT system. The labour requirement is minimal

PERTANIKA VOL. 8 NO. I, 1985 143

E.S. LIM

particularly for seeding and preparation of thetroughs for reuse. Labour cost is one of themajor expenses in the soilless production of crops(Lim and Wan, 1984). Therefore the rapidcleaning of the system would reduce labourrequirements considerably particularly whencompared with other soilless systems requiring asolid medium to support the plants. The solidmedium inevitably become covered with algaegrowth and requires laborious cleaning before itcan be reused. With the NFT troughs, the coversprevent algae growth within the troughs and therockwool cubes are discarded after each crop.The convenience and simplicity in the use of theNFT trough are significant advantages especiallywhen large scale application of the soilless cul-ture technique is contemplated.

The potential of the NFT trough design isevident. Its productive capabilities are no lessthan that of the successful H-system of soillessproduction used locally. In the studies, thesystem has shown definite advantages when com-pared to the H-system. These advantages,besides those already mentioned in respect oflabour savings also include the low constructioncosts and capital outlay. In addition the use of asmall volume of nutrient solution can result inconsiderable savings in the costs of nutrient saltsnecessary especially when compared to systemsusing deep solution. The NFT troughs are alsosuitable for large-scale commercial crop produc-tion or for use on a small-sca.le as a roof-top orbalcony garden for the hobbist.

CONCLUSION

The nutrient film technique can be success-fully applied to the cultivation of crops in thetropics. However, the conventional polythenegullies used in the temperate countries cannotbe used locally because of the high internal tem-perature resulting from the intense splar radia-tion. The insulated NFT trough that was design-ed in this study, effectively controlled the heatbuild up in the root zone.

The NFT troughs have been found to beversatile and capable of grdwning various vege-table and ornamental species successfully. Theuse of the NFT trough is easy with low labourrequirements. Planting and replanting can berapidly carried out.

The NFT troughs are also easy to construct.The parts necessary for the construction arelocally available and the capital outlay for thesystem is extremely small when compaed to otherlocally available systems.

ACKNOWLEDGEMENTS

The author gratefully acknowledges theassistance of Encik Maarouf A. Wahid in thepreparation of the photographs for publication.

REFERENCES

COOPER, A. (1982): Nutrient Film Technique.London, Grower Books.

GERICKE, W.F. (1940): The Complete Guide toSoilless Gardening. London, Putnam.

HARRIS, D. (1970): Hydroponics: The Garden-ing Without Soil. Cape Town, Purnell.

LlM, E.S. (1982): Soilless cultivation of vege-table crops. In: Vegetables and Ornamentalin the Tropics. Universiti Pertanian Malay-sia, Serdang, Selangor. pp. 137 - 144.

LlM, E.S. and WAN, C.K. (1984): Vegetableproduction in the tropics using a two-phase

substrate system of soilless culture. Proceed-ings of the Sixth International Congress onSoilless culture. Wageningan, ISOSC. pp.317-328.

SHOLTODOUGLASJ. (1976): Advanced Guide toHydroponics (Soilless Cultivation). London,Pelham Books.

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development of an nft system of soilless culture for the tropics

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