Pertanika 15(3), 207-216 (1992)

N and P Nutrition of Gmelina arborea Roxb. Seedlings on Latosolic Soil.II: Effects of N and P Fertilizers and their Combinations

on Histochemical Properties.

CHUKS I. OGBONNAYA1

Faculty of Forestry, Universiti Pertanian Malaysia43400 UPM Serdangy Selangor Darul Ehsan, Malaysia

Keywords: Gmelina arborea, histochemical properties, latosolic soil, N and P nutrition.

ABSTRAK

Kesan-kesan paras baja N dan P dan kombinasinya yang berbeza terhadap sifat-sifat histokimia anak benihGmelina arborea Roxb. di atas tanah latosolik telah disiasat. Fmpat paras (0.00, 9.50, 19.00 dan 28.50g/pot)N dan P telah digunakan dalam semua kombinasi yang mungkin. N telah digunakan sebagai kalsium amoniumnitrat (Ca(NHJ2 NOJ dan P sebagai superfosfat (Ca(HfO)Hfl)). Sukatan N dan P yang sama (N2P2)menghasilkan gentian yang paling panjang. Penggunaan N tanpa P meningkatkan garispusat gentian dan saizlumen gentian. Semua perlakuan tersebut telah menambah ketebalan dinding gentian yang begitu ketara dalamhubungan terhadap kawalan. Semua perlakuan tersebut telah mengurangkan pekali kelembutan dan meningkatkannisbah runkel berbanding dengan kawalan. Penggunaan P semata-mata sahaja meningkatkan nisbah kekecilannya.N semata-mata sahaja tidak menghasilkan apa-apa perbezaan yang ketara. Nilai yang paling tinggi diperolehidengan N2P2. Kadar pH kayu telah dikurangkan oleh semua perlakuan manakala larutan alkohol benzene,larutan alkali (1 % NaOH), dan larutan air panas telah ditingkatkan oleh pembajaan. Penilaian menyeluruh(holistic) terhadap perlakuan-perlakuan tersebut menunjukkan bahawa pembajaan anak benih G. arborea diatastanah latosolik dengan N dan P tidak memperbaiki/meningkatkan sifat-sifat histokimia yang berkaitan (relevant)dengan pengeluaran/penghasilan palpa dan kertas bila dibangdingkan dengan kawalan. Manakala prestasikebanyakkan kombinasi treatment adalah homogen dengan kawalan, ada sedikit kombinasi yang menunjukkanprestasi yang ketara rendah daripada kawalan. Bagaimana kombinasi terbaik yang diperoleh ialah N0P3 danN1PL

ABSTRACT

The effects of different levels of N and P fertilizers and their combinations on the histochemical properties of Gmelinaarborea Roxb. seedlings on latosolic soil were investigated. Four levels (0.00, 9.50, 19.00 and 28.50 g/pot) of Nand P were applied in all possible combinations. N was applied as calcium ammonium nitrate (Ca(NH4)2NO^ andP as superphosphate (Ca(H2POJ H2O). Equal doses of N and P (N2P2) produced the longest fibres. Applicationof N without P increased fibre diameter and fibre lumen size. All the treatments significantly increased fibre wallthickness in relation to the control. All the treatments reduced coefficient of suppleness and increased runkel ratio incomparison with the control Application ofP alone raised slenderness ratio. N alone did not produce any significantdifferences. The highest value was obtained with N2P2. Wood pH was reduced by all the treatments while alcoholbenzene solubles, alkali (1 % NaOH) solubles, and hot water solubles were increased by fertilization. Holisticassessment of the treatments showed that fertilizing G. arborea seedlings on latosolic soil with N and P did notimprove the histochemical properties relevant to pulp and paper production when compared with the control Whilethe performances of most of the treatment combinations were homogeneous with the control, a few combinationsperformed significantly lower than the control The best treatment combinations were, however, obtained as N0P3 andN1PL

'Present address: Plant Ecology Unit, School of Biological Sciences, Imo State University, PMB 2000, Okigwe, Nigeria.

CHUKS I. OGBONNAYA

INTRODUCTIONGmelina arborea Roxb., commonly known asgmelina, belongs to the family Verbenaceae.Gmelina is exotic to Nigeria and was introduced asa firewood plant from tropical Asia (Gledhill 1972).

G. arborea is a valuable tree for timber and hasfeatured prominently in plantation forestry inNigeria. At the end of 1986 over 100,000 hectaresof the species had been established on planta-tions (Adegbehin et al 1988). The wood is one ofthe best utility timbers of the tropics, useful forhardboards, plywood core stock and veneers suit-able for light construction, general carpentry,packaging and furniture fitments (Rassaque andKhan 1977).

G. arborea is also very valuable as a matchwoodand in Nigeria it has been found to be superior toPopulus nigra, a traditional timber for matchmak-ing (Anon. 1965). Most importantly, gmelina hasgood pulping characteristics and because of thisits large-scale cultivation to supply the existingand proposed paper-mills in Nigeria and in otherparts of the tropics has been encouraged (Anon.1970).

The roles of N and P in plant growth anddevelopment have been widely studied. It is knownthat N is an essential constituent of proteins andnucleic acid which are the core of life processes(Novoa and Loomis 1978). P plays a key role inenergy metabolism. It is incorporated intoadenosine triphosphate (ATP), and it is part andparcel of the universal 'energy currency' of allliving cells of whatever species (Epstein 1972).

It is necessary to see the importance of thenutrient elements not merely in terms of theirindividual and separate actions but in terms oftheir interactions with each other and with cli-mate and environmental conditions (Hewitt 1963).The maximum effect of one particular elementmay not be as expected if the supply of otherplant nutrients is not adequate. For this reasonthe ratio in which plant nutrients are applied infertilizers is also important. This ratio depends onnumber of factors such as soil fertility status, inaddition to plant species (Mengel and Kirkby1979).

The main objective of the study, therefore,was to determine the response of G. arborea seed-lings to different levels of N and P, and theircombinations on latosolic soil. It was hoped thatthe result would be of practical value in recom-mending a balanced dose of N and P fertilizers tothe potting medium and at the initial stages ofgrowth in the field for this species which is by far

one of the most promising fast-growing tree plantsin the tropics.

MATERIALS AND METHODS

Potting Medium and Seedlings

Latosolic soil was used as the growth medium.The soil was sun-dried for a week andundecomposed plant materials were removed. Thesoil was potted into 12.5-litre plastic buckets withdrainage holes at the bottom and adequatelywatered. Two-week-old seedlings (at 2-leaf stage)showing uniform height growth were transplantedinto the pots. Each pot received only one seed-ling. The physical and chemical properties of thesoil are shown in Table 1.

TABLE 1Physical and chemical properties of the

experimental soil

Properties

Physical Properties

Sand (%)Silt (%)Clay (%)Textural class

Chemical Properties

pH (1:1H2O)PH(1:1KC1)Organic matter (%)Total N (%)Avail. P (ppm)Exch. Cations (meq/lOOg soil)

KNaCaMg

Effective CEC (meq/lOOg soil)

Latosolic Soil

64.503.30

32.30clay-loam

4.403.531.420.032.11

0.741.770.596.164.17

Treatments

Four levels (0.00, 9.50, 19.00 and 28.50 g/plantcorresponding to 0, 1,2 and 3 levels respectively)of N and P were applied in all possible combina-tions and permutations. The levels were chosento present the presumed optimum range for thisspecies after a preliminary trial on the soil type.The complete dose for each treatment was givenat one instance, and both nutrients were appliedat commercial grades. N was applied as calcium

208 PERTANIKA VOL 15 NO. 3, 1992

EFFECTS OF N & P FERTILIZERS AND THEIR COMBINATIONS ON HISTOCHEMICAL PROPERTIES

ammonium nitrate (CAN) (Ca (NH4)2 NO,), P assuperphosphate (Ca(H2PO4).H2O). The nutrientswere applied in granular form in trenches about2 cm deep made around the seedlings, and cov-ered with a thin layer of soil.

Measurement of Assessment ParametersHistological Properties of Wood and the Derived ValuesStemwood samples for the fibre studies were ob-tained at the second internode from the base andimmediately fixed with standard formalin-aceticacid-alcohol (FAA) preservative until needed formaceration. Small slivers or slices for macerationwere obtained form the outer part of the stem(inside the bark) and thoroughly washed withdistilled water to remove excess fixative. The sliv-ers were placed into test-tubes containing 10 ml60% nitric acid and boiled in a water bath for tenminutes. Macerated materials were washed severaltimes with distilled water to remove the acid.Small quantities of the macerated material wereplaced on a clean slide, gently teased out andstained with 1:1 aqueous safranin-glycerol solu-tion (Okoegwale and Gill 1988). The preparedslide was viewed with a calibrated microscope.

Fibre length (fl), fibre diameter (fd), fibrelumen diameter (fid) and fibre wall thickness(fwt) were measured in millimetres (mm) usingan eyepiece micrometer. At X 100 and X 400magnification one division of the eyepiecemicrometer amounted to 0.01 mm and 0.0025mm respectively. Thirty fibres were measured persample and mean values calculated.

The following values were obtained from thefibre dimensional measurements:

a) slenderness ratio or relative fibre length: thiswas computed by using the formula (Rydholm1967)

SR =fibre length

fibre diameter

b) Coefficient of suppleness (CS) or flexibilitycoefficient: this was obtained with the for-mula (Petri 1952)

fiber lumen diameterCS=- X 100

fibre diameter

c) Rukel ratio (RR) : this was caculated with theformula (Okereke 1962)

2 X fibre wall thicknessRR =

fibre lumen diameter

Chemical PropertiespH of Wood

Gmelina wood converted to 40 mesh sawdust wasused for the determination of pH. 5g (oven-dryweight) was stirred in double distilled water (25g)and left to stand for 30 minutes with occasionalstirring. The pH was measured with the glasselectrode of a pH meter (Pye Unicam, PW9418model) after standardization with buffer solutions.An average of 3 readings was obtained (Anon.1980)

Ash Content of Wood

Loss-on-ignition method was used for the deter-mination ol percentage ash content, lg of groundwood passed through 40 mesh, dried at 105°C inthe oven, was ignited in a muffle furnace at 500°Cfor 3 hours. The ash content was calculated asfollows (Allen et al 1974):

Ash content (%) *ash weight (g)

X 100oven-dry weightof sample (g)

Alcohol-benzene Soluble Substances Content (%)TAPPI, T6 m-59 method was used (Grant 1961).lg of oven-dried (105°C for 24 hours) groundwood passing through 40 mesh was extracted insoxhlet apparatus with 100 ml of a mixture of 33ml 95% alcohol and 67 ml benzene for 8 hours.At the end of the extraction the solvent systemwas distilled off and the residue dried at 105°Cuntil a constant weight was obtained. The amountof residue was expressed as a percentage of thetotal plant material used for the extraction.

Alkali (1% NaOH) Soluble Substances Content (%)The test was carried out by digesting 1 g of oven-dried sawdust (passing a 40 mesh screen) in 100ml of 1% NaOH solution on a water bath at 100°Cfor exacdy 1 hour with three stirring periods.After digestion the material was filtered andwashed in a water and 10% acetic acid solution.The residue was dried at 85°C until a constantweight was obtained. The weight of the residuewas expressed as a percentage of the total plant

PERTANIKA VOL. 15 NO. 3, 1992 209

CHUKS L OGBONNAYA

sample used for the extraction (Casey 1960).

Hot Water Soluble Substances Content (%)The method employed was TAPPI, Tl m-59 (Grant1961). lg of oven-dried sawdust (passing a 40mesh screen) was placed in a conical flask fittedwith a reflux condenser. 100 ml of distilled waterwas added and the flax was then immersed in aboiling water-bath for 3 hours. After the boilingperiod the material was filtered and washed sev-eral times with hot water and dried at 85°C untila constant weight was obtained. The loss in weightexpressed as a percentage of the oven-dried mate-rial was the matter soluble in water.

Experimental Design and Statistical Procedure

The experiment incorporated a 42 factorial de-sign based on randomized blocks with each treat-ment replicated 5 times. The basic factors N andP were the main effects while NXP was the inter-action. The pots were laid out (lm apart) on agrassy field at the University of Port HarcourtBotanical Garden. A total of 80 pots, includingthe control, was used for the 16 treatment combi-nations.

The parameters measured were subjected toanalysis of variance to determine if there weresignificant differences between nutrient elementsor nutrient elements* interaction. Next, a leastsignificant difference (LSD) test was performedon the treatments to determine if means weresignificantly different from each other. 'CRISP'statistical package, using the IITA computing sys-tem was used in carrying out the data analysis.

Holistic Assessment of Measured Parameters

The results obtained were subjected to holisticanalysis in order to obtain a conclusive view. Foreach parameter measured the treatment effectsincluding the control were scored according totheir relative performances. The scores rangedfrom 1 for the worst treatment effect to 16 (cor-responding to the total number of treatments)for the best treatment effect. The total score foreach treatment was obtained, on the basis ofwhich comparisons were made and conclusionsdrawn (Ogbonnaya 1990).

RESULTS

Fibre Dimensional Properties

There was very strong significant variation due toN, P and their interactions on fibre length (fl).The values obtained ranged from 0.56 ± 0.03mm(control) to 0.83 ± 0.00 mm (N2P2). The LSD (P= 0.05) between the means was obtained as 0.038

mm. Applications of P without N significantlyenhanced fl when compared with the control,similarly N alone significantly improved fl at N2P0and N3P0 while N1P0 did not. Combinations of Nand P also increased significantly the fl with theexception of N3P3 (0.59 ± 0.03mm) combination(Table 2).

Analysis of variance showed that the differenttreatments of N, P and their interactions broughtabout significant (P = 0.01) variations on the fibrediameter (fd). The LSD (P = 0.05) among themeans was recorded as 0.0022 mm (Table 2). Inrelation to the control all levels of P alone andN1P0 did not affect fd. Combinations of N and Pgave erratic responses and the values ranged from0.22 ± 00mm (N2P1) to 0.027 ±0.001 mm (N1P2).

Significant variations (P = 0.01) on fibre lu-men diameter (fid) as a result of the differenttreatments of N, P and their combinations wereobtained. The three levels of N without P pro-duced the same value (0.017 ± 0.001 mm) whichwas not significantly different from the controlvalue (0.016 ± 0.002 mm). Application of P aloneadversely affected fid. The values recorded for Nand P combinations were highly variable andranged from 0.014 ± 0.00 (N2P1) to 0.018 ± 0.001mm (N3P1) (Table 2).

Variations due to the various applications ofN, P and their interaction on fibre wall thickness(fwt) were also significant (P = 0.01). The LSD (P= 0.05) between the means was 0.4 X 10'3mm(Table 2). All the values obtained with N, P andtheir combinations were significantly higher thanthe control. The values ranged from 2.97 X10-3mm (N0P0) to 4.72 x 10'3mm (N1P2).

Derived Values from Fibre Dimensions

Coefficient of suppleness (CS) showed significant(P =0.01) variations due to N, P and their interac-tions. The LSD (P = 0.05) between the means wasobtained as 3.7305. The control produced thehighest CS and this was significantly higher thanthe rest of the treatments with the exception ofN1P0, N1P3 and N3P0 (Table 3).

The variations in slenderness ratio (SR) dueto N, P and their interactions were significant (P= 0.01), and the LSD (P = 0.05) between themeans was 2.2114 (Table 3). Application of Palone raised SR with reference to the control,while N alone did not produce any significantdifferences. The values recorded with the combi-nations ranged from 22.48 ± 1.04 (N1P2) to 31.94±0.87 (N2P2).

210 PERTANIKA VOL. 15 NO. 3, 1992

EFFECTS OF N & P FERTILIZERS AND THEIR COMBINATIONS ON HISTOCHEMICAL PROPERTIES

TABLE 2Effects of N and P fertilizers and their combinations on fibre length, fibre diameter, fiber lumen

diameter, and fibre wall thickness of wood of Gmelina arborea seedlings raised on latosolic soil.

NutrientCombinations

NOPO

PI

P2

P3

N1P0

PI

P2

P3

N2P0

PI

P2

P3

N3P0

PI

P2

P3

LSD (P=0.05)

Fibrelength(mm)

0.56 ±0 .03

0.66 ± 0.02

0.64 ±0.01

0.63 + 0.02

0.58 ±0.01

0.68 ±0.07

0.61 ±0.02

0.70 ±0.02

0.60 ± 0.02

0.66 ±0.01

0.83 ± 0.00

0.71 ±0.001

0.61 ±0.001

0.74 ±0.02

072 ±0.02

0.59 ±0,03

0.038

Fibre

Fibrediameter

(mm)

0.022 ±0.001

0.023 ± 0.00

0.023 ±0.001

0.022 ±0.001

0.024 ±0.001

0.023 ±0.00

0.027 ±0.001

0.026 ±0.001

0.025 ±0.001

0.022 ± 0.00

0.026 ±0.001

0.024 ±0.002

0.025 ±0.001

0.024 ±0.001

0.025 ±0.001

0.024 ±0.001

0.0022

dimensions

Fibre lumendiameter

(mm)

0.016 ±0.002

0.014 ±0.00

0.015 ±0.004

0.014 ±0.00

0.017 ±0.001

0.015 ±0.00

0.017 ±0.002

0.018 ±0.001

0.170±0.001

0.040 ± 0.00

0.016 ±0.001

0.016 ±0.002

0.017 ±0.001

0.014 + 0.001

0.015 ±0.00

0.016 ±0.001

0.0014

Fibre wallthickness(xl0'3mm)

2.97 + 0.35

3.90 ±0.16

4.07 + 0.30

4.16 ±0.14

3.93 ±0.19

3.93 ±0.19

4.72 ±0.22

4.24 ±0.43

3,97±0.12

4.29 ±0.16

4.81 ±0.27

4.22 ±0.50

3.79 ±0.11

4.05 ±0.31

4.47 ± 0.26

4.10 ±0.31

0.400

The results on runkel ratio (RR) showedsignificant variation due to the different treat-ments of N, P and their interaction at P = 0.01.Application of P alone significantly (P = 0.05)increased RR as compared with the control. Thelowest RR was obtained with the control (0.38 ±0.05) and the highest (0.59 ± 0.07) with N2P2.The LSD (P = 0.05) among the means was ob-tained as 0.0923 (Table 3).

Chemical Properties

pH values did not show any significant variationdue to P application. The variations due to N andNXP interaction were rather significant at P =0.01, and the LSD (P = 0.05) between means wasrecorded as 0.847 (Table 4). Application of N at2nd and 3rd levels significantly lowered wood pH,while the values obtained with the 1st level and alllevels of P alone were homogeneous with the

PERTANIKA VOL. 15 NO. 3, 1992 211

CHUKS L OGBONNAYA

TABLE 3Effects of N and P fertilizers and their combinations on coefficient of suppleness,

slenderness ratio and runkel ratio of Gmelina arborea seedlings raised on latosolic soil.

NutrientCombinations

NOPO

PI

P2

P3

N1P0

PI

P2

P3

N2P0

PI

P2

P3

N3P0

PI

P2

P3

LSD (P=0.05)

Coefficient ofsuppleness

71.4118.30

60.20 ± 8.94

64.4112.13

63.1412.16

68.8312.24

64.9412.61

63.0613.02

68.2712.16

66.9411.98

62.1811.88

63.0312.55

66.1814.46

69.17 + 4.07

59,0712.93

58.78 12.52

65.7812.80

3.7305

Derived fibre dimensional values

Slendernessratio

25.55 12.90

28.8810.67

27.8411.02

28.6111.8

23.72 10.89

30.7211.84*

22.4811.04

27.1810.99

24.0510.99

29.8311.02

31.9410.87

29.2012.01

24.8111.02

30.4311.27

28.5311.53

24.7911.78

2.2114

Runkelratio

0.3810.05

0.5710.02

0.58 10.03

0.5510.33

0.47 10.05

0.5310.04

0.55 10.06

0.4810.05

0.48 + 0.01

0.6210.04

0.59 ± 0.07

0.53 10.05

0.45 + 0.03

0.56 10.05

0.61+0.03

0.52 10.08

0.0923

control. Combinations of N and P in all cases(except N3P2) significantly reduced the pH incomparison with the control, and the value rangedfrom 4.22 (N2P1) to 4.87 (N3P2).

The variations due to the effects of N and Papplications on wood ash content were significantat P = 0.01 and P = 0.05 respectively. The interac-tion between them was not found significant.The LSD (P = 0.05) among the means was 0.67%.N. when applied alone reduced significantly the

ash content of gmelina wood in relation to thecontrol. P alone was the most important nutrientelement required by the plant to enhance ashcontent. The values obtained with N and P werehomogeneous with the control (Table 4).

Application of N, P and their combinationsignificandy raised alcohol-benzene soluble sub-stances content (ABSS) with the exception ofN1P2, N3P3, N1P1 and N2P2. The highest value(8.34%) was obtained with N3P3. Analysis of vari-

212 PERTANIKA VOL. 15 NO. 3, 1992

EFFECTS OF N & P FERTILIZERS AND THEIR COMBINATIONS ON HISTOCHEMICAL PROPERTIES

TABLE 4Effect of N and P fertilizers and their combinations on pH, ash content, alcohol-benzene solubility,

alkali ( 1 % NaOH) solubility and hot water solubility of wood of G, arboreaseedlings raised on latosolic soil

NutrientCombinations

NOPO

PI

P2

P3

N1P0

PI

P2

P3

N2P0

PI

P2

P3

N3P0

PI

P2

P3

LSD (P=0.05)

WoodPH

5.53

5.40

5.36

5.15

4.95

4.40

4.40

4.23

4.40

4.22

4.45

4.30

4.10

4.65

4.87

4.40

0.847

Ash contentof wood

(%)

2.00

3.80

3.60

3.50

1.00

2.50

2.40

1.80

1.10

1.90

1.80

1.75

1.30

2.10

2.40

2-10

0.672

Chemical properties

Alcohol-benzenesolubility

2.45

6.21

4.40

4.34

6.19

5.65

3.70

4.24

7.45

4.24

4.09

5.21

6.49

6.74

7.17

8.34

1.835

Alkali(INaOH)solubility

16.80

19.65

19.10

15.65

20.07

21.25

49.35

18.75

21.35

19.70

19.25

18.00

21.80

20.67

21.20

22.85

2.187

Hotwater

solubility

8.63

12.00

11.10

11.10

11.72

11.17

10.22

10.41

13.47

9.74

9.90

11.47

11.50

11.62

12.38

12.77

2.082

ance showed significant variation due to N and P,and none for the interaction. The LSD (P = 0.05)between the means was recorded as 1.835% (Ta-ble 4).

Analysis of variance in alkali (1% NaOH)soluble substances content did not indicate anysignificant variation due to the various treatmentsof P and NxP interaction, while the variation due

to N application was significant (P = 0.05). TheLSD obtained among the means was 2.187%.Nitrogen therefore was the most important nutri-ent element responsible for increased ASS ofgmelina wood on latosolic soil.

Variations of hot water soluble substancescontent (HWSS) due to N and P application weresignificant while those due to their interactions

PERTANIKA VOL. 15 NO. 3, 1992 213

CHUKS I. OGBONNAYA

TABLE 5Holistic assessment of the effects of N and P fertilizers and their combinations

on the histochemical properties of G. arborea seedlings on latosolic soil.

Nutrient combinations and performance scoresParameters

Fibre lengthFibre diameterFibre lumen diam.Fibre wall thickness

NOPO

1161116

N0P1

10134

14

N0P2

81379

N0P3

71647

N1P0

2101512

N1P1

11137

12

N1P2

61

152

N1P3

123

165

N2P0

46

1511

N2P1

101644

N2P2

163

111

N2P3

1310116

N3P0

166

1515

N3P1

15104

10

N3P2

14673

N3P3

310118

Coeff. of supplenessSlenderness ratioRunkel ratio

166

16

395

884

6118

142

14

91510

718

137

13

123

13

413

1

5163

111210

155

15

2146

1102

104

11

p H of woodAsh content of woodAlcohol-benzene

solubilityAlkali solubilityHot water solubility

168

1615

1

1516

69

13

1415

10127

1314

11167

121

77

12

813

848

812

15105

36

13134

82

23

16

27

1382

96

14113

44

9149

13

52

10

1010

46

11

1112

35

14

810

11

15

Mean score* 11.5 9.75 9.58 10.0 9.0 7.5 9.0 9.83 7.92 7.0 8.16 9.42 9.0 8.5 7.33 7.67

* The Least Significant Difference (LSD) between the means scores was obtained as 3.65 at P = 0.05

were not. All the treatments except N1P2, N1P3,N2P1 and N2P2 produced significantly higherHWSS than the control. The LSD (P = 0.05)between the means was 2.082% (Table 4).

Holistic Assessment

Holistic or overall assessment of the perform-ances (Table 5) showed that all the treatmentsproduced histochemical properties that were nobetter than the control. Least significant differ-ence test showed that N1P2, N2P1, N3P2 andN3P3 were significantly (P = 0.05) worse than thecontrol, while the rest of the treatments werehomogeneous with the control. The best combi-nations, however, were N0P3 and N1P1.

DISCUSSIONFibre Dimensions

The longest fibres in the study were obtained withNP nutrient combinations, and N2P2 gave thehighest value (0.83 * 0.00 mm), while shorterfibres were recorded when P and N were appliedalone. Apparently both N and P are required forimproved fibre length of gmelina on latosolic soil.The role of both elements in cell development iswell known. N increases the rate and extent ofprotein synthesis required for cell division andelongation (Hewitt 1966) while P as a constituent

of nucleus plays an important part in cell divisionand development (Epstein 1972).

N and NP combinations were responsible forthe widest fibre and fibre lumen diameters whileP produced the least values. Large fibre diameter,however, is undesirable in pulp and paper manu-facture since it reduces slenderness ratio(Rydholm 1967). Fibre wall thickness was signifi-cantly increased by all the treatments in relationto the control. This result is equally undesirablein pulp and paper production since it tends toincrease the runkel ratio and thereby reducespaper strength (Okereke 1962). The increasedfibre dimensions when N was supplied alone orwith P can be explained on the basis that carbohy-drates are utilized to form more protoplasm whenN is in adequate supply. Cells produced undersuch conditions tend to be large (Letham 1961).

The Derived Values from Fibre DimensionsThe highest CS was obtained with the control(NOPO) which was homogeneous with the valuerecorded with N1P0, N1P3 and N3P3. All thevalues obtained were, however, greater than 50.According to the guidelines by Petri (1952),Okereke (1962) and Rydholm (1967) CS > 50 butpreferably greater than 60 is required of fibres forpaper-making, because paper strength tends toimprove with increasing CS. Such fibres with high

214 PERTANIKA VOL. 15 N O . 3, 1992

EFFECTS OF N 8c P FERTILIZERS AND THEIR COMBINATIONS ON HISTOCHEMICAL PROPERTIES

CS are flexible, collapse easily and produce goodsurface contact and fibre-to-fibre bonding. Withthe results obtained in this study the CS wouldgenerally produce good quality paper.

SR was depressed when N was applied aloneor at N1P2 and N3P3 combinations. The rest ofthe treatments increased the ratio in comparisonwith the control, and these treatments are there-fore expected to produce papers with better tear-ing resistance, since the higher the SR, the strongerthe resistance to tearing (Rydholm 1967).

With reference to the control, all the treat-ments (except N1P0 and N0P3) significantly en-hanced RR. All the values obtained, however,were < 1. Going by the recommendations ofOkereke (1962) and Rydholm (1967), the fibresproduced by all the treatments would make goodpaper, as the RRs were less than unity in eachcase. Since paper quality increases with decreasein RR, it is therefore expected that plants treatedwith N fertilizer alone would produce better qual-ity paper.

Chemical Properties

The pH of sap of many plant species is in therange of about 5-5.5 which is slighty acidic (Mengeland Kirkby 1979). The result obtained showedthat P alone did not affect wood pH while N andits combinations with P (except N3P2) signifi-cantly reduced wood pH in relation to the con-trol. The increased pH with N and its combina-tion with P can be explained on the basis of thefact that NO3 when assimilated (reduced) by plantroots yields NO3" ion which is a very strong acidicradical. On the other hand phosphate fertilizerswhen reduced in acidic soil (like the latosolic soil,pH 4.4) yield HPO4

2', which is a weak acidicradical rather than the stronger H2PO4 radical,and hence the higher pH recorded with P ferti-lizer. Acidity of wood plays some part in the pulpand paper industry in relation to corrosion ofequipment and excessive consumption of alkalinecooking liquor in alkaline puling (Anon 1980).

Results of the study show that ash content ofgmelina wood was significantly increased by Palone, significantly reduced by N alone and wasnot affected by NP combinations in relation tothe control. Wood ashes contain 2-8% K^O, P2O.and a large amount of CaO (Wilde 1958). Highash content recorded with seedlings treated withP fertilizer can therefore be appreciated. The ashof wood is of interest as a measure of the totalmineral content (Allen et al 1974). Wood ash isalso used as fertilizer and in glass and soap manu-facture (Anon. 1974/75).

Fertilizer applications increased soluble sub-stance content of gmelina wood in relation to thecontrol. Alcohol-benzene soluble substances(gums, fats, waxes and resins) are mainly lipids ortheir derivatives. The roles of N and P in thesynthesis of fatty compounds namely lipoproteinsand phospholipids respectively are well known.Alcohol-benzene solubles are of great importancebecause high value adversely affects the pulpingprocess and the quality of the resulting pulp(Grant 1961). The alkali soluble substances madeup of pentosans, hexosans and lignin (Casey 1960)and the hot water soluble substances consisting ofcarbohydrates, sugar and salts (Grant 1961) aremainly carbohydrates or their derivatives. Theincreased concentrations of these compounds areinconsistent with the fact that supply of N toplants decreases carbohydrate content since theyare used to form more protoplasm and cells(Letham 1961). Ulrich (1954), however, observedthat the depressing effect of N on carbohydratecontent may not be found with low or moderateapplication of N. High percentage alkali solublesubstance predisposes the wood to decay and inthe sulphite pulping process, yields are reducedand more alkali is consumed. Hot water solublesubstances give no direct information on the pulpvalue, but do indicate the nature of certain con-stituents present in the wood.

CONCLUSIONHolistic assessment of the treatments showed thatfertilizing G. arborea seedlings on latosolic soilwith N and P did not improve the histochemicalproperties relevant to pulp and paper productionwhen compared with the control. While the per-formance of most of the combinations was homo-geneous with the control, a few performed signifi-cantly worse than the control. The best treatmentcombinations were, however, N0P3 and N1P1.

ACKNOWLEDGEMENTS

The author is grateful to the Faculty of Forestry,Universiti Pertanian Malaysia for the facilities usedin preparing the manuscript while on an Aca-demic Exchange Fellowship of the Association ofCommonwealth Universities.

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(Received 3 September 1991)

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