physical and chemical properties of coconut coir dust and...

PertanikaJ. Trap. Agric. Sci. 27(2): 121 - 133 (2004) ISS : 1511-3701© Universiti Putra Malaysia Press

Physical and Chemical Properties of Coconut Coir Dust and Oil Palm EmptyFruit Bunch and the Growth of Hybrid Heat Tolerant Cauliflower Plant

IASIAH A., 2MOHD. RAZI, I., 3MOHD. KHANIF Y,4MARZIAH M. & 5SHAHARUDDIN M.

1Agrotech and BioSciences Division,2Department of Crop Science,

3Department of Lana Management,4Department of Biochemistry, Universiti Putra Malaysia,

43400, UPM, Serdang, Selangor, Malaysia5Malaysian Institute For Nuclear Technology Research,

Bangi, 43000, Kajang, Selangor, Malaysia

Keywords: Coconut coir dust, oil palm empty fruit bunch, growing medium, soilless culture,cauliflower

ABSTRAK

Penyelidikan yang dilaporkan dalam eksperimen ini memberi tumpuan terhadap ciri fizikal dan kimia habuksabut kelapa (CD) dan tandan kosong kelapa sawit (EFB) berpotensi digunakan sebagai media pertumbuhanbagi kobis bunga hibrid di bawah rumah tanaman di tropika yang mempunyai kelembapan udara yang tinggi.EFB dan CD mempunyai ciri fizikal optimum untuk keperluan pertumbuhan tanaman pada awal penanaman.Walau bagaimanapun, kedapatan air tersedia bagi CD adalah 34 % dibandingkan dengan 19% untuk EFB.Ruang rongga tersedia EFB , iaitu rongga yang melebihi 300 11m adalah tinggi dibandingkan dengan CD. Cirikimia menunjukkan EFB adalah lebih alkali (PH 6.9) dibandingkan dengan CD(PH 5.3) dan rendahkekonduksian elektrik (EC) iaitu 1.3 dSm,l dibandingkan dengan CD (1.9 dSm,l). Keputusan juga menunjukkanCD mengandungi kepekatan nutrien yang tinggi dibandingkan dengan EFB. Walaupun EC asal CD lebihtinggi, jumlah bahan kering tanaman adalah tinggi dibandingkan dengan kobis bunga yang ditanam dalamEFB. Kedapatan fungi dan cendawan pada permukaan media EFB dan penguraian awal telah menyebabkanpertumbuhan tanaman yang kurang pada media EFB. Oleh itu, CD adalah media tanaman yang lebih sesuaidibandingkan dengan EFB untuk penanaman hibrid bunga kobis.

ABSTRACT

This research report is about the physical and chemical properties of coconut coir dust (CD) and oil palm emptyfruit bunch (EFB), and their potential for use as growing media for hybrid cauliflower grown under humidtropical greenhouse conditions. The physical properties showed that both the EFB and CD provided optimum plantgrowth conditions at the start of the growing the period. However, the readily available water value for CD was34% whereas that for EFB was 19%. The air filled porosity containing more pores larger than 300 11m werehigher in EFB compared to CD. The chemical properties data suggested that EFB was more alkaline (PH of 6.9)than CD (PH of 5.3) and had lower electrical conductivity (EC) of 1.3 dSm-1 than CD (l.9 dSm,l). The resultsalso indicated higher nutrient contents in CD than in EFB. Despite a high initial EC value for CD than EFB,the hybrid cauliflower plant dry weights and total leaf area for CD grown plants were double those grown in EFB.The appearance offungus and mushroom on the EFB medium surface and the early sign of decomposition mayaccount for the lower plant growth in the EFB medium. Hence, CD is a more suitable growing medium for growinghybrid cauliflower compared to EFB.

INTRODUCTION

The principal difference in growing conditionsbetween plants grown in other media and those

raised in soil is the amount of space available forroot development. In many cases thedevelopment of roots is restricted by the

ASIAH A., MOHD RAZI, I., MOHD. KHANIF Y., MARZIAH M. & SHAHARUDDIN M.

container, pot or holding medium in which theplants are raised (Carlile 1997). The root ofplants must obtain sufficient water, oxygen andnutrients from the surrounding environment.The life processes of the root system excreteCO

2and other gases that must disappear within

a certain time from the root environment. Thestructure of the growing medium must be softand porous enough so that roots can easilypenetrate widely into the material and it mustalso provide anchorage and support for theplants. The well being of a plant is stronglydependent on the correct functioning of theroot system. The physical, chemical and biologicalproperties of a growing medium can be used asa basis of classifying the suitability of a growingmedium in relation to the needs of the roots.

Understanding the physical environmentsurrounding roots in containers (relative volumeof air, water, and solid) is based on the relationshipbetween energy status and water content of themedium (Roberts et al. 1989). This relationshipis a reflection of the pore size distribution of themedium. A plot of this relationship, i.e., a plotof volumetric wetness (q) vs. water potential iscalled moisture characteristic curve or moistureretention curve (De Boodt and Verdonck 1972).

Ever since Bunt (1961) first reportedmoisture retention curves for pot-plant media,there has been considerable effort to determinethe utility of these curves in explaining plantgrowth, and the best way to quantifY these datafor both descriptive and predictive purposes(Roberts et al. 1989). The phase distribution(air, water and solid) of a medium is importantfor horticulture particularly at matric potentialsbetween -1 cm and -100 cm water column (pF2.0 = 10 kPa) (De Boodt et al. 1974; Michiels etal. 1993). Lower matric potentials will give riseto severe loses in growth rate. Air filled porosity(AFP) of the medium is the ability of the mediumto retain air, hence is important to ensuresufficient oxygen supply to the roots. As far asthe chemical properties are concerned thegrowing medium must have a suitable pH valuerange of about 5.0-6.5, an electrical conductivitythat may not exceed a certain level and free ofharmful elements and chemicals.

The physical and chemical properties ofcoconut coir dust (CD) from numerous sourceshave been found to be within acceptable rangesand suitable for use as growing medium (Evanset al. 1996). However significant differences were

observed among coconut coir dust Sources with_ respect to physical and chemical properties

(Evans et al. 1996), and these may explain thedifferences in results (good and negative)obtained from previous studies (Reynolds 1973;Meerow 1994; Radjaguguk et al. 1983) whenusing CD as growing media. Yahya and MohdRazi (1996) suggested that the variation inchemical and physical properties of the mediaand differences in plant sensitivity to a definedroot environmental condition might havecontributed to the marked differences in someornamental plant development observed in theirstudies. Therefore, the properties of the growingmedium affect the plant growth.

Although CD and its mixture with othercomponents have been widely and successfullyused in different parts of the world as anenvironment friendly peat substitute for growingplants in containers (Meerow 1994, 1995), itsbasic properties and utilization in cropproduction in Malaysia is rather scarce (Yahyaand Mohd Razi 1996). Another potential mediumis oil palm empty fruit bunch (EFB). It is one ofthe solid wastes generated from the oil palmindustry. Even though direct mulching usingEFB on soil can improve soil structure, aerationand moisture capacity (Megat Johari et al. 1990)there has been little interest on utilisation ofEFB as growing medium for containerized plants.

The objective of this study was to determinethe differences in physical and chemicalproperties between the local CD and EFB, andtheir effect on the growth and nitrogen contentin the hybrid cauliflower when used as growthmedia. In many cases the properties of CD weremanipulated to prepare suitable coir based mediafor containerized plant (Handreck 1993; Meerow1994, 1995; Yahya et al. 1997). However, in thisstudy no manipulation was done to improve thebasic properties of the medium by mixing withother organic and inorganic components.

MATERIALS AND METHODS

Experiment 1: Determination of Physical and

Chemical Properties

Coconut coir dust (CD) obtained locally fromPerak and freshly shredded oil palm empty fruitbunch fibres of mean gross length 9.10 ± 3.40cm obtained from Kapar Klang were used in thisstudy. Oil palm fibres were cut to a mean grosslength of 3.46 ± 1.26 cm by an impact typecutter at a cutting speed of 2 kg/min. Short

122 PERTANlKAJ. TROP. AGRIC. SCI. VOL. 27 NO.2, 2004

PHYSICAL AND CHEMICAL PROPERTIES OF CD AND EFB FOR GROWING HYBRID CAULIFLOWER

fibres were then ground through 5.0-mm sieveand air-dried. The products are referred to as oilpalm empty fruit bunch (EFB). Both CD andEFB were analysed for physical and chemicalproperties. Bulk density (g cm-3

) was determinedusing modified methods of De Boodt et al.(1974). The cylinder used was a brass ring, 4.0cm in height and 7.60 cm (internal diameter),with internal volume of 181 ml. The bottom ofthe ring was fitted with iron gauze and rubberring and the whole assembly were weighed.Another ring was then placed on top of theabove-mentioned ring and stacked vertically. Therings were filled with a medium and gentlytapped against a laboratory table at a height of:::::: 10.0 cm a sufficient number of times to obtaina certain bulk material in the bottom ring. Thetop ring was discarded. The bottom ring filledwith medium was weighed and then seated on tothe porous plate and saturated with water for 48hours. The mass was determined after dryingthe medium in the oven at 105° C for 24 hours.

The particle density of the substrates wasdetermined by using a pycnometer bottle (Blakeand Hartge 1986). All determinations werereplicated five times. The total pore space(volume %) and volumetric shrinkage (volume%) were calculated following the methods ofMichiels et al. (1993).

The moisture retention curves of bothcoconut coir dust and oil palm empty fruitbunch were determined using the method of DeBoodt et al. (1974). The moisture content wasmeasured after equilibrating the samples on thepF equipment at matric potentials of -10, -50, 100, -300 cm water column and 15 bar (pF 1,1.7, 2.0, 2.5 and 4.2). From this curve, the airvolumes, readily available water, water buffercapacity, less readily available water and poresize distributions were calculated (Michiels et al.1993).

The pH and electrical conductivity (EC) ofthe coconut coir dust and oil palm empty fruitbunch were determined using air-dried samplesto water ratio of 1:2 (v/v). The samples werestirred with a glass rod and allowed to equilibratefor 4 hours. For pH measurement, the sampleswere stirred again immediately before measuringthe pH using a calibrated pH meter. For ECmeasurement, the solution was then filteredthrough a Whatman No.41 filter paper and theextract was collected in a small beaker. The ECof the extract was measured using the EC probewith calibrated conductivity meter.

Total nitrogen was determined using SemiMicro Iqedahl., potassium (K+) contents usingflame photometer and calcium (Ca2+),magnesium (Mg2+) and zinc (Zn2+) contents usingabsorption following HN0

3-H

20

2digestion of

the coconut coir dust and oil palm empty fruitbunch in the microwave. Phosphorusconcentration (P) was determined colorimetricallyby vanadium molybdate measured at 410 nmwith a spectrophotometer.

Five replications were tested for eachmedium (coconut coir dust and oil palm emptyfruit bunch). A t-test for two independent samples(two tailed test, a = 0.05) was done to determineif the medium significantly affected the measuredphysical and chemical properties.

Experiment 2: Growth Comparison of Hybrid Cauliflower Grown in Coconut Coir Dust and Oil PalmEmpty Fruit Bunch

a. Plant Materials, Growth Conditions andTreatmentsWhite polyethylene bags of 6 L volume wereused as growing bags. A 10 cm circular openingwas made at the top of each bag after filling with6 L of growing medium (100% coconut coirdust or 100% empty fruit bunch) to plant thehybrid cauliflower seedling. Slits were made atthe bottom of each bag to allow for drainage.The coconut coir dust or oil palm empty fruitbunch was then thoroughly wet with water andallowed to drain before seedling transplanting.Each bag was placed on a perforated squareplastic basket fitted with 6 legs of 4 cm highfrom the greenhouse floor.

Seeds of hybrid heat tolerant cauliflowerwere germinated in germination trays filled with100 % coconut coir dust or 100% oil palmempty fruit bunch and watered daily with tapwater. Two weeks after germination, uniformsized seedlings were transplanted, one seedlingper bag, into the 6 L growing bags filled withcoconut coir dust or oil palm empty fruit bunch.

The growing bags were placed in agreenhouse under natural photoperiod andirradiance with day temperature ranging between28°C and 38°C and minimum night temperatureof 25°C. The seedlings were irrigated via dripemitter (2 L h-1

) with tap water for the first 3days and a complete Cooper (1979) nutrientsolution thereafter. Nitrogen was applied as KN0

3

at a concentration of 200 ppm N. The nutrientsolution was adjusted to pH ranging from 5.5 to

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 27 NO.2, 2004 123

ASIAH A., MOHD RAZI, 1., MOHD. KHANIF Y, MARzIAH M. & SHAHARUDDI M.

5.8 with either dilute KOH or H2S04 , The

electrical conductivity of the solution was 2.4 dSm,l. Initially plants were irrigated twice daily for15 minutes but as the environmental conditionspromoting evapotranspiration increased and theplants grew larger fertigation was increased tothree times/day. The experimental design was arandomized complete block design with the twogrowth medium as treatments each replicatedfive times.

b. Plant Samplings, Growth Parameters andChemical AnalysisPlants were harvested at 21, 42 and 65 days aftertransplanting (DAP). The plants were cut justbelow the first leaf node, which was less than 1cm from the growing medium surface. Five plantsof each treatment were harvested at eachharvesting time and separated into stem pluspetioles, leaves and curd at final harvest. Mterweighing, the plant samples were dried in aforced air oven at 70° C for 96hr and weighed.The dried samples were ground through a 2mm sieve for total N analysis.

RESULTS

The physical and chemical properties of coconutcoir dust were evaluated as potential growingmedium for containerized plants and comparedto oil palm empty fruit bunch. The bulk densityof oil palm empty fruit bunch (0.075 g cm·3) wassignificantly higher than that of coconut coirdust (0.177 g cm,3) as shown in Table 1. Oilpalm empty fruit bunch also showed asignificantly higher particle density (1.321 g cm,3)compared to 0.758 g cm'3 for coconut coir dust.The total pore space for organic mediumincluded the open, interconnecting and closedpores. Data in Table 1 show that coconut coirdust had significantly higher total pore space(96.26 %vol.) than oil palm empty fruit bunch

(92.80% voL). No significant difference wasfound in volumetric shrinkage values betweencoconut coir dust and oil palm empty fruitbunch. The volumetric shrinkage values for thecoconut coir dust and oil palm empty fruitbunch were 11.21 % and 10.13% respectively.

The moisture retention curves for coconutcoir dust and oil palm empty fruit bunch areshown in Fig. 1. As suction was gradually increasedmore water was drawn out of the oil palm emptyfruit bunch compared to the coconut coir dust,resulting in the low amount of water retained inoil palm empty fruit bunch as compared tococonut coir dust. Increasing suction will resultin the progressive emptying of the pores ofdifferent sizes until at high suction values whereonly the narrow pores retain water. Hence, theshape of the moisture retention curve of amedium reflects its pore size distribution(Michiels et ai. 1993).

From the moisture retention curves obtainedfor coconut coir dust and oil palm empty fruitbunch, its pore distributions were calculated.Fig. 2 shows the distribution of pore size for oilpalm empty fruit bunch and coconut coir dust.It is clear that oil palm empty fruit bunchcontained relatively larger pores (> 300 11mdiameter) than coconut coir dust, and oncethese large pores are emptied at a given suction,only small amounts of water remained.

This is reflected in the results as only 45%water was retained in oil palm empty fruit bunchat 1 kPa suction compared to 71 % water retainedin coconut coir dust as shown in Fig. 1. The airfilled porosity (AFP) represented by relativelylarger pores> 300 mm in oil palm empty fruitbunch was 47% whereas the AFP in coconut coirdust was only 25% (Fig. 2).

The coconut coir dust contained more poresof sizes between 60 mm and 300 mm than oilpalm empty fruit bunch which resulted in a

TABLE 1Physical properties of coconut coir dust and oil palm empty fruit bunch

Property

Bulk density (g cm'3)Particle density (g cm-3)Total pore space (% vol)Shrinkage (% vol)

Coconut coir dust

0.0740.758

96.26411.206

Oil palm empty fruit bunch

0.1771.321

92.79610.129

t- value

3.790**2.659*2.932**0.729NS

The figures are means of 5 replications.ns, *, ** on significant or significant at p< 0.05 or 0.01, respectively.

124 PERTANlKAJ. TROP. AGRIC. SCI. VOL. 27 0.2,2004


100

80

20 ---

co~ 0

'>- 60

oo 2 3 4 5

p V lu

Fig. 1: Moisture characteristic curve for coconut coir dust. and oil palm empty fruit bunch ...

AFP

~-

Coconut dust ~EAW '"---

LRAW

~TEmpty fr It bunch ==-

T

WBC~..,..

u<..7<..J<r

60

50

40

i~ 30

CI>E:::s(5>

20

10

o<30 30 - 60 60 - 300 > 300

Pore diameter (micron)

Fig. 2: Air jilled porosity (MP), Easily available water (EA"J, Water buffer capacity (WEe) and Lessreadily available water (LRA"J for coconut coir dust and oil palm empty fruit bunch at different

pore size distribution. The values are means of 5 replications and standard errors are shown



higher readily available water (RAW) value of34% compared to 20% for oil palm empty fruitbunch.

However, both coconut coir dust and oilpalm empty fruit bunch showed almost similarvalues of pore size between 30 mm and 60 mmwhich decreased the water buffer capacity. Thewater buffer capacity for coconut coir dust andoil palm empty fruit bunch was 6% v/v and 5%v/v, respectively. Narrow pore sizes of < 30 mmwas also high in coconut coir dust than oil palmempty fruit bunch, hence coconut coir dustretained more less readily available water (LRAW)of 31 % compared to 22% for oil palm emptyfruit bunch.

There was a marked difference between thegrowing media with respect to chemicalproperties (Table 2). One factor indirectlyaffecting plant growth is the pH of the growingmedium. The pH differed significantly betweencoconut coir dust and oil palm empty fruitbunch samples (Table 2) with pH ranging from5.3 to a high value of 6.9 respectively. Therecommended pH range for an ideal substratewas between 5.2 and 6.3 ( Abad et al. 1989).Therefore, the pH value of oil palm empty fruitbunch was higher than the established limits foran ideal substrate whilst coconut coir dust waswithin the range.

The EC level of the coconut coir dust (1.96dSm- l ) was high though within the range forideal substrate as compared to the EC of 1.30dSm-1 for oil palm empty fruit bunch. Theamount of naturally-occurring nutrients incoconut coir dust was significantly higher thanoil palm empty fruit bunch with potassium (K+)

content of 2.39%, being the highest for allnutrients measured. The concentration of P andCa2

+ in coconut coir dust was 0.41 and 0.18%respectively and for oil palm empty fruit bunch0.23 and 0.08%. Hence, the high EC value ofcoconut coir dust as compared to oil palm emptyfruit bunch observed in the present study couldbe due to the higher concentrations of thesenutrients in coconut coir dust compared to thatin the oil palm empty fruit bunch. Coconut dustcontained 0.11 % magnesium (Mg2+), which wassignificantly different from the 0.05% Mg2+

content in oil palm empty fruit bunch. The Mg2+

content was lowest in both coconut coir dustand oil palm empty fruit bunch in comparisonto other nutrients. Total nitrogen (N) was slightlyhigher in oil palm empty fruit bunch comparedto that in coconut coir dust. Since the nutrientscontent in both media is low, the nutrientrequirements of plants growing in these mediamay be supplied by fertigation (liquid feeding)during plant growth.

An attempt was made to evaluate thepotential of these two substrates for use asgrowing media by planting hybrid caulifloweron both media and supplying both with completenutrient solution including nitrogen at 200 ppmin a subsequent experiment.

Differential growth responses were observedbetween the two growing media studied (Figs. 3and 4). Plants grown in coconut coir dustexhibited higher morphological growth than oilpalm empty fruit bunch. Leaf and stem dryweight were 49% and 42% less in oil palm emptyfruit bunch respectively compared to coconutcoir dust at 21 DAP (Fig. 3a). These resulted in

TABLE 2Chemical properties of coconut coir dust and oil palm empty fruit bunch

Property Coir dust Oil palm empty fruit t- valuebunch

pH 5.3 6.9 3.751**Electrical conductivity (dS m- l

) 1.96 1.30 3.973**Total nutrient (%):Total nitrogen 0.39 0.42 2.870*P 0.41 0.23 3.406**K+ 2.39 1.56 2.507*Ca2+ 0.18 0.08 2.499*Mg2+ 0.11 0.05 2.859*

The figures are means of 5 replications.*, **, Significant at P<0.05, or 0.01 respectively.

126 PERTANlKAJ. TRap. AGRIC. SCI. VOL. 27 NO.2, 2004

0.3

0.1

PHYSICAL AND CHEMICAL PROPERTIES OF CD AND EFB FOR GROWING HYBRID CAUUFLOWER

0.5 .,-----------=----total plant

(a)

0.4

ccuc...9-J:en.~ 0.2

~o

Coconut coir dust Oil palm empty fruit bunch

Growing medium14 .,----------0:;:-------------....,

(b)

Coconut coir dust Oil palm empty fruit bunch

Growing medium

Fig. 3: Growth of hybrid cauliflower in coconut coir dust or oil palm empty fruit bunch at (a) 21and (b) 42 DAP with 200 ppm N. The values are means of 5 replications

and standard errors are shown. Note the different scales of Y axes

a significantly (p<O.Ol) higher above-ground totalplant dry weight of plant grown in coconut coirdust compared to oil palm empty fruit bunch(Fig. 3a). Total leaf area for coconut coir dustplant was higher than that in oil palm emptyfruit bunch at 21 DAP (Fig. 4).

The growth rates for hybrid cauliflowerplants grown in either coconut coir dust or oilpalm empty fruit bunch did not show any distinctdissimilarly. However differences were observedin dry weight accumulation. There wassignificantly higher dry weight accumulation instem and leaves of plants grown in coconut coir

dust compared to those grown in oil palm emptyfruit bunch at 42 DAP (Fig. 3b). These resultssuggest greater plant growth response to coconutcoir dust compared to oil palm empty fruitbunch growing medium. Total plant dry weightand total leaf area for plant grown in coconutcoir dust were double that grown in oil palmempty fruit bunch (Fig. 3b).

In addition, plant growth in oil palm oilpalm empty fruit bunch experienced damagedue to fungal and mushroom growth in themedium at about 30 to 35 DAP (Figs. 6a, 6b and6c). The experiment was terminated after 42

PERTANIKAJ. TROP. ACRIC. SCI. VOL. 27 NO.2, 2004 127


-

-T

- coconut coir dust empty fruit bunch.,..

~

-

PVV''?

10

NE~Cll! 100CllCll(l)

..J

10000

1000

21 42

Days after transplanting (DAP)

Fig. 4: Total leaf area of cauliflower grown in coconut coir dust or oil palm emptyfruit bunch at 21 and 42 DAP supplied with 200 mg t1N. The values are

means of 5 replications and standard errors are shown

DAP due to excessive fungal and mushroomproblems in the oil palm empty fruit bunchgrowing medium. Therefore data at 65 DAP wasnot available.

The results in Figs. 5a and 5b show that thetotal N uptake in the leaf of hybrid cauliflowerplants was affected by the growing medium.Total N uptake in the leaf at 21 and 42 DAP wassignificantly higher in plants grown in coconutcoir dust than in plants grown in oil palm emptyfruit bunch. Total N uptake in the leaf per plantranged between 10.0 to 20.0 mg dry weight forplants grown in oil palm empty fruit bunch andcoconut coir dust respectively. Total N uptake inthe stem per plant was lower than in the leaf forall plants grown whether in coconut coir dust oroil palm empty fruit bunch. However, total Nuptake was 30% higher in the stem of plantsgrown in coconut coir dust than that in oil palmempty fruit bunch.

The high dry weight accumulation in theplant grown in coconut coir dust (Fig. 3a and3b) resulted in double the total N uptake in theplants grown in coconut coir dust as com-paredto the plants grown in oil palm empty fruitbunch at both 21 and 42 DAP.

DISCUSSION

During the growing period, the physicalproperties of the substrate cannot be changedwhereas the chemical properties can be keptunchanged or varied by adding nutrients.Therefore, at the start of the growing period,the physical properties of the substrates have tobe in an optimal condition (Ulrich 1996).

Both coconut coir dust and oil palm emptyfruit bunch were evaluated as lightweightmaterials with bulk density varying between 0.074g cm-3 and 0.180 g cm-3, respectively (Table 1).The values were lower than the range for idealsubstrates (Abad et ai. 1989). However, thecoconut coir dust bulk density was within therange (0.04 to 0.08g cm-3

) reported by Evans etal. 1996 for five coconut coir dust sources fromthe Philippines and by Patricia et ai. (1997) forcoconut coir dust from Mexico (0.075g cm-3)

and Sri Lanka (0.056g cm-3). The advantage ofthe light weight material is that it allows ease ofhandling and transport, which is a very importantcommercial or economic consideration duringhandling and transport. Despite their low bulkdensity, both coconut coir dust and oil palm

128 PERTANlKAJ. TROP. AGRIC. SCI. VOL. 27 NO.2, 2004


30

25~cC'IlQ. 20zC)

.§. 15Gl~C'Il~

10Q.:3

~0 5~

z

0

700

600....c 500C'IlQ.z

400C)

.§.Gl 300~

:lQ.:::l 200~,g 100z

0

(a)

total plant

leaf

stem

Oil palm empty fruit bunch Coconut coir dust

Growing medium

(b)

Oil palm empty fruit bunch Coconut coir dust

Growing medium

Fig. 5: Total nitrogen uptake in the leaf, stem and total plant of hybrid cauliflower plantgrown in coconut coir dust or oil palm empty fruit bunch at 21 (a) and 42 (b) DAP

supplied with 200 ppm N. The figures are means of 5 replications andstandard errors are shown. Note the different scales of Y axes

empty fruit bunch did not show any problems toanchor of cauliflower plants.

Both the particle and bulk densities of oilpalm empty fruit bunch were significantly higherthan coconut coir dust (Table 1). These couldbe attributed to the different materialcomposition of the two media. For most organicsubstrates, however the particle density is theparameter with the least quantum with respectto limitations on plant growth (Michiels et al.1993) .

The total pore space, which can be filledwith water and air for both coconut coir dustand oil palm empty fruit bunch, wascharacteristically high (Table 1). Therefore bothmedia should have sufficient amounts of air andavailable water for plant growth. The valueobtained for coconut coir dust was 96 vol %which was close to the 95.3 vol % obtained by

Prasad (1997) and between 95.1 to 96.3 vol %byPatricia et al. (1997) for coconut coir fromMexico and Sri Lanka. Furthermore, the totalpore space has been reported to show smallchanges over time for black, white peat andsphagnum (Michiels et al. 1993) when usingthose substrates in an ebb/flood irrigation system.

Air filled porosity (AFP) , readily availablewater (RAW), water buffer capacity (WBC) andless readily available water (LRAW) are thephysical properties that have a direct effect onplant growth. It is usually recommended that airfilled porosity (AFP) for growing medium inhorticulture should be above 10-20% (De Boodtand Verdonck 1972; Bugbee and Frink 1986).The air content of the medium is particularlyimportant when plants are grown for long periodsof time in containers. In this study, the AFP wasestimated to be above 25% in both coconut coir

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 27 0.2,2004 129

ASIAH A., MOHD RAZI, I., MOHD. KHANIF Y, MARZIAH M. & SHAHARUDDIN M.

dust and oil palm empty fruit bunch (Fig. 2) andthus sufficient for growing hybrid cauliflowerplant which has a long maturity period of 65 - 70days. The AFP of the oil palm empty fruit bunchwhich contains more pores of size> 300 J.lm washowever, much higher than coconut coir dustwith difference of 47% (Fig. 2).

The results showed that the optimal valuesof RAW were 34% for coconut coir dust and19% for oil palm empty fruit bunch. The waterbuffer capacity (WBC) values obtained for bothcoconut coir dust and oil palm empty fruitbunch are adequate (Bunt 1988). Hence, it isexpected that plants grown in these media willnot be prone to drastic wilting if there is asudden increase in transpiration when thewatering regime is not adjusted. Based on theresults of this study and other evidence adducedso far, it is reasonable to suppose that the physicalproperties of both coconut coir dust and oilpalm empty fruit bunch are optimum at thestart of growing period.

The results for chemical properties of bothcoconut coir dust and oil palm empty fruitbunch indicate wide differences between thetwo growing media (Table 2). The pH, throughits effect on the availability of major and minornutrients from growing medium, is ofconsiderable importance to plant growth. Theresults shown in Table 2 indicate that oil palmempty fruit bunch is more alkaline (pH of 6.9)compared to coconut coir dust (pH of 5.3). Thiswould favour coconut coir dust as a more suitablegrowing medium than oil palm empty fruit bunchsince the optimal pH for plant growth in mostsubstrates is 5.0-5.5 (Carlile 1997). On the otherhand, high electrical conductivity (1.9 dS mol)for coconut coir dust may pose a problem byretarding plant growth. Fewer problems mayoccur with oil palm empty fruit bunch with itslower EC value of 1.3 dS m-l.

Earlier (Evans et al. 1996; Meerow 1995)and recent studies (Abad et al. 2002) on coconutcoir dust naturally occurring nutrients werereported to be low in mineral nitrogen (N),calcium (Ca2+) and magnesium (Mg2+) and canbe improved by using fertilisers such as calciumnitrate, magnesium nitrate, magnesium sulphateor gypsum. These researchers also reported highlevels of phosphorus (P) and potassium (K+)content in coconut coir dust tested. Otherresearchers have also reported low levels of N,Mg2+ and P but high K+ content in oil palm

empty fruit bunch (Megat johari et al. 1990).The results, however, indicated higher nutrientcontents with the exception of total nitrogen incoconut coir dust compared to oil palm emptyfruit bunch (Table 2).

The results on hybrid cauliflower plantgrowth in coconut coir dust or oil palm emptyfruit bunch suggest that coconut coir dust is amore suitable growing medium than oil palmempty fruit bunch (Figs. 3a, 3b and 4). Despitethe high initial EC value of coconut coir dust,no indication of growth retardation in hybridcauliflower plant was observed. Under theseconditions, plant dry weight and total leaf areawere double in plants grown in coconut coirdust compared to those grown in oil palm emptyfruit bunch. High yields have also been reportedfor Calceolaria grown in different mixtures ofcompost with commercial substrates (1:2 ratio)having higher EC values of 5.60 and 4.95 dS m-l

(Gomez et al. 2002). These researchers suggestedthat the cations and anions contributing to theEC in commercial substrate were mainly nutrientssuch as K+ and N0

3-N, and thus had a beneficial

effect of over compensating for the osmoticeffect.

Recently, Noguera et al. (2000) reportedthat the excess soluble salts is easily and effectivelyleached from the coconut coir dust materialunder customary irrigation regimes when usedfor ornamental plants in containers or 'growingbags' for tomatoes, flowers, etc., in gardengreenhouses. In this study, it has been suggestedthat frequent fertigation applied to the mediummay effectively leach out the excess soluble saltin coconut coir dust. Nevertheless, a high K+content in coconut coir dust as seen in Table 2may contribute to a high EC but not to excesssalinity, which may have caused an osmoticimbalance.

From the results of this study, it is postulatedthat the lower growth response of hybridcauliflower plant to oil palm empty fruit bunchat 21 DAP could be due to high rates ofimmobilisation of soluble N by micro-organismsin the oil palm empty fruit bunch medium. Thisis reflected in lower total N uptake in the leafand stem of plants grown in oil palm empty fruitbunch in comparison to those grown in coconutcoir dust (Figs. 5a and 5b). Thus, it was assumedthat the liquid feed of 200 ppm N applied to theoil palm empty fruit bunch medium was notenough to compensate for a consistently highrate of N immobilisation.

130 PERTANlKAJ. TRap. AGRIC. SCI. VOL. 27 NO.2, 2004


Since both coconut coir dust and oil palmempty fruit bunch are organic materials, theproperties of both media may change due todecomposition of organic matter in the substrateduring the growing period. A high pH level of5.9 to 6.9 resulting from applying large amountsof lime was shown to increase the decompositionrate of sphagnum peat, which finally reducedplant growth in comparison to the low pHbetween 4.4 and 5.2 (Anon 1997). The samephenomenon may have occurred with oil palmempty fruit bunch which was characterised witha high pH of 6.9 (Table 2) and lower plantgrowth response at 42 DAP when compared tococonut coir dust as shown in Fig. 3b.

Visual observations during this studyindicated that after 30 DAP the growing bagscontaining oil palm empty fruit bunch mediumflattened out and started to show early signs ofdecomposition. In contrast, the coconut coirdust medium stayed fluffy. This shows that thechanges in properties of the oil palm empty fruitbunch are more rapid than the coconut coirdust growing medium, which indicates a lack ofbio-stability in the oil palm empty fruit bunch.

Lemaire (1995) reported that lack of biostability may cause severe volume loss resultingin compaction, reductions in air volume, readilyavailable water, porosity, particle size alteration,increases in pH and salinity due to mineralizationand also change in the gaseous phasecomposition due to carbon dioxide production.These changes in properties may finally reducethe plant growth (Lemaire 1995). Thus the lowhybrid cauliflower plant growth in the oil palmempty fruit bunch observed in this study may bedue to the changes in the properties during thegrowing period.

High content of lignin, between 37% and50% dry weight, was reported by Abad et ai.(2002) in the coconut coir dust from differentsources whilst lower values of 22% and 25% inthe oil palm empty fruit bunch were reported byZainon et ai. 1998 and Megat ]ohari et ai. 1990.Lignin is resistant to microbial degradation. Thuscoconut coir dust is most likely to be more biostable than oil palm empty fruit bunch due toCD's higher lignin content. Evidence of a veryhigh bio-stability index of 100 for coconut coir

dust, which related to high C/N ratios, and highlignin content in the coconut coir dust has alsobeen reported by Lemaire (1997).

Other factor that account for the low hybridcauliflower plant growth in the oil palm emptyfruit bunch was the appearance of fungus andmushroom on the medium surface. In contrastthere was no fungal and mushroom growth incoconut coir dust even until 42 DAP.

It is expected that a high pH of 6.9 for theoil palm empty fruit bunch may be suitable forstrong development of certain fungi andmushroom observed in the present study (Figs.6a, 6b and 6c). This is in agreement with otherstudies using peat medium which provide optimalgrowth of mushroom like fungi, cup fungi (orderPezizales) and agarics (order Agaricales) in theprocessed peat medium at high pH values ofbetween 6.5 and 7.5 and temperature above 20°C (Schlechte 1997). The mycelium of thesefungi and mushroom grow vigorously in thesubstrates which may become hardened,impervious to water and deficient in nutrientssuch as nitrogen and potassium (Schlechte 1997).Hence the hybrid cauliflower plant grown in oilpalm empty fruit bunch with thick coverings ofthe mycelium in the growing bag showedretarded growth (Fig. 3).

CONCLUSIONS

The results presented show that the physicalproperties of both coconut coir dust and oilpalm empty fruit bunch are optimum at thestart of the growing periods. However, differencesin chemical properties between the two mediawere more obvious compared to other properties.Under these conditions and with continuousliquid feed high in N content, the hybridcauliflower grew better in 100 % coconut coirdust than 100% oil palm empty fruit bunch.Moreover, coconut coir dust was free from fungiand mushroom-like fungi during the growingperiod of cauliflower. It can be concluded thatcoconut coir dust can be used directly as growingmedium whereas oil palm empty fruit bunch hasto be composted, to achieve biostability. Hence,coconut coir dust is a more suitable growingmedium for growing hybrid cauliflower than oilpalm empty fruit bunch.


ASIAH A., MOHD RAZI, I., MOHD. KHANIF Y., MARzIAH M. & SHAHARUDDI M.

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(Received: 21 October 2003)(Accepted: 1 June 2005)

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