' ho - }\lever,

/

ArlS!. For. Res., 1987,17,203-14 '.

. . ' .This file, About Th'

M,' Was created b

IS File'. Early Growth and Nutrient Status of Eucalyptus saligna as affected by Nitrogen and Phosphorus Fertilisation

sscan·S I.dentified Y scanning the -'

some . by the Softw

Prtnted publ' .mistakes are have b I

Catlon., - may remain

een corrected;. ,

R. S. Yost,A D. S. DeBell,B C. D. WhitesellC and S. C. MiyasakaD

A Department of Agronomy and Soil Science, University of Hawaii, 1910 East-West Road, Honolulu,

Hawaii 96822.

B USDA Forest Service, Pacific Northwest Experiment Station, Olympia, Washington, U S.A

.cUSDA Forest Service, Pacific Southwest Forest and Range Experiment Station, Honolulu,

.

Hawaii.

D Cornell University; formerly with the Bioenergy Development Corporation, Hilo, Hawaii.

Abstract

Growth responses of Eucalyptus saligna to nitrogen and phosphorus fertilisers were assessed in newly established bioenergy plantations in Hawaii. Fenilisers were applied three times (0, 6, and 15 months after planting) at four rates (0, 25, 50 and 75 g urea per tree and 0, 30, 60 and 90 g triple superphosphate per tree). Phosphorus increased growth only during the first 9 months, but nitrogen increased height and diameter and also their periodic increments through 48 months. The growth increment peaked during the 18-24 month period, and declined drastically thereafter. Maximum growth was obtained in the 50 g urea treatment, with tree biomass averaging

if 22·5 kg and yield per hectare averaging 94 t at 48 months.

Production may have been greater feniliser had been applied after 15 months. Nutrient status and its relationship with growth were evaluated using percentage composition and

DRIS indices. Nitrogen applications increased concentrations and the DRlS indices of most nutrients at 12, 18 and 24 months. In general, DRIS indices for nitrogen and phosphorus were more strongly related than concentrations to present size and past growth at 12, 18 and 24 months. Future growth increment, however, tended to be more highly correlated with nutrient concentrations than with DRIS indices, especially for the 24-48 month period.

[O.D.C. 181.65 + 181.341 :(114.262 + 114.263): 178.83 Eucalyptus saligna]

Introduction

Short-rotation culture of Eucalyptus is being evaluated to provide biomass for conversion to energy in Hawaii. Impressive growth has been obtained in some plantings (Walters 1973; Schubert and Whitesell 1985), but a number of fertiliser trials in Hawaii (Qureshi 1978; Miyasaka 1984) and elsewhere (Cromer 1971; Cremer et al. 1978; Schonau 1983; Ward et al. 1985) have indicated that nitrogen and phosphorus are the nutrients which most commonly limit Eucalyptus growth. Thus, fertilisers will probably be required for optimum production on many sites.

On abandoned sugarcane land in Hawaii where recent short-rotation culture studies of Eucalyptus have been established, N-P-K fertilisers are routinely applied at the time of planting and again 6-9 months later. However, the dosages or .--'. -.

combinations ofN and P that are optimum for E. saligna and other trees in Hawaii have not been determined. Moreover, technology for assessing nutrient status of '.'." ;'''':-soils and/or plant tissues as guides for fertiliser recommendations has not been

developed for Eucalyptus plantings. The study described here provides some . . . '-. ' . . ". ..... ground work to aid in meeting these needs.

In this study, we tested nitrogen and phosphorus fertilisers in factorial combinations and assessed the effects on individual tree growth and on stand

204 R. S. Yost er al.

growth. In addition, we examined the influence of fertiliser treatments on nutrient concentrations and nutrient balances in foliage, using the DRIS (Diagnosis and Recommendation Integrated System) method proposed by Beaufils (1973). Finally, we compared nutrient concentrations with indices in their correlation with past and future growth, to assess their usefulness for guidance in nutrient management decisions.

Study Area

The study was established near Akaka Falls, about 15 km north-east of Hilo, on an area typical of much marginal and abandoned sugarcane land along the Hamakua coast (19· 30'N, 155" 15'W) of Hawaii Island. The elevation of the planting site was about 480 m, and the annual rainfall averages 5000 mm, distributed fairly evenly throughout the year. The slope was less than 10%. The soil series was Akaka silty clay loam (thixotropic, isomesic typic Hydrandept) and was slightly acidic (pH 5·7-6·0). Usually this soil is more acidic (pH -5·0), but 4·5 Mg ha -1 of crushed coral (92% CaC03) had been applied a bout 1 year before the Eucalyptus trees were planted. The amounts of exchangeable calcium were also unusually high (4 cmol (+) kg-1 in the subsoil) because of the coral application. The total nitrogen concentration in the surface soil was similar to or slightly lower than that of most other soils along the Hamakua coast, averaging about 0·4%; extractable phosphorus (0· 005 N H2S0

.... ,

Early Growth of E. saligna 205

N, 0, 150, 300 and 450 kg ha-1;

P, 0,75, 150 and 115 kg ha-1;

K, 200 kg ha-1.

Diameter at breast height (d) and height (h) measurements were taken on the inner 25 trees in each plot at 9 and 12 months and then subsequently at 6-month intervals through 48 months. Mean values of d and h were calculated for each plot, and periodic growth was calculated by the difference between the means for two periods. Survival was calculated as the percentage of live trees remaining on the inner plot at each measurement. Tree biomass, or dry weight D W (total above-ground dry matter, including foliage for each measured tree), was estimated from the equation:

10&:(DW)= -3· 8604+0·9644 10&(d2h).

This equation was developed from trees of comparable age and size (n = 93, R2= 0·99, RMSE=O·l l , this last value for the root mean square error being in terms of the natural logarithm of tree dry weight). Weights of all measured trees on each plot were summed and averaged.

Samples of young, fully expanded leaves were collected from the upper crowns of 10-15 trees in the interior of each plot at 9,12,18 and 24 months. Dried foliage was analysed-at the University of Hawaii for tota! concentrations of macronutrients (for N by a standard Kjeldahl procedure and for P, S, Ca, Mg and K by X-ray emission spectroscopy).

Nutrient contents of the foliage were expressed as percentage dry weight and also in terms of DRIS indices. These indices compare ratios of nutrients in a sample with 'norm' ratios obtained from a desirable (usually high-yielding) population (Beaufils 1973; Sumner1977). In our case, the desirable population was taken as the upper decile of the E. saligna cumulative growth to 24 months in the experimental treatments (Table 1). This period was selected because it represents a highly responsive period of growth and yet integrates growth over sufficient time for the tree-soil-weather system to achieve a measure of stability. All ratios with other nutrients were included in the calculation of each index, thus compensating to some extent for 'dilution' and 'luxury consumption' phenomena. The indices were calculated as follows (Sumner 1977).

(1) Intermediate functionsf(xly) were calculated by comparing the ratio of two nutrient elements x and y in the leaf tissue with the same ratio in the desirable population (the 'norm' ratio): (a) if the sample ratio of nutrient concentrations NIP was greater than the nornJ. ratio nip thenf(N/P) was given by

f(NIP)=100X{(NIP)/(nlp)-1}X lO/CV, ( la)

where CV was the coefficient of variation of the norm ratio in the desirable population; (b) if the sample ratio N/Pwas less than the norm ratio nip then the relation* was

f(N/P) = 100X l1-(nlp)/(NIP)} X lO/CV. (lb)

Intermediate ratios were calculated for each ratio of nutrient elements included in the index. * Note that equation (lb) corrects a typographical error in the corresponding equation published earlier in this Journal by Ward et al. (1985).

'''.,

Table 1.

N

Ca Mg

NIP N/K N/Ca N/Mg N/S P/K PiCa P/Mg PIS KlCa KlMg KlS CalMg CalS Mg/S

Mg index = {-J(N/Mg)

R. S. Yost et at.

Norm values used in computation of DRIS indices for 24-month-old E. saligna

The norm values for the desirable population were taken from the upper 10% of the plots with respect to diameter at breast height (dbh). The foliar nutrient contents are given as percentage dry weight, and all nutrient ratios are included. CV is

coefficient of variation

Maximum

7·37 11·50 79·10

1·52 0·16 1·28 0·67 0·33 0·15

7·93 10·13 1·55 2·57

3·36 6·08 9·55 11·69

0·15 0·29 0·68 1·20 2·28

4·95 4·31 10·08

2·44 5·40 2060

(2) The intermediate functions were then combined to form the diagnostic indices:

N index = lJ(N/P) + j(N/K) + j(N/Ca) +j(N/Mg) + j(N/S)I!S,

P index.={ -j(N/P) + j(P/K)+ j(P/Ca)-+-f(P.'Mg)-+-f(P/S)I!S,

K index = {-j(N/K) -f(P/K) + j(KlCa) -+-j(K/Mg) -+-j(KJS)l/S,

Ca index ={ -j(N/Ca)-j(p/Ca) -j(KlCa)-+-j(Ca/Mg)+ J(CalS)I/S,

-J(P/Mg) -J(KlMg) -j(Ca/Mg) +J(MglS)l/S,

S index = {-J(N/S) -J(P/S) -j(KlS) -J(Ca/S)-j(Mg.'S)I!S.

Note that in order to form the DRIS indices the intermediate functionsJexly)are added if the nutrient is in the numerator or subtracted if the nutrient is in the denominator. The indices then have the property that they sum to zero for each leaf sample. Nutrients presumably can be ranked from most-deficient to adequate, based on the values of their indices; negative indices imply deficiencies and the

206

Quantity Mean value CV Minimum

Tree height (m) 10·27 8·89 Tree dbh (mm) 70·77 6·35 65·50

Nutrient content (%) 1·22 12·86 1·03

P 0·14 10·59 0·12 K 1·09 9·96 0·95

0·57 8·68 0·51 0·27 11·60 0·22

S 0·12 11·47 0·10

Nutrient ratios 8·72 6·70 1·13 18·90 0·87 2·13 12·57 1·85 4·56 20·63

9·47 8·46 0·12 15·22 0·10 0·24 10·76 0·21 0·52 18·01 0·39

1·09 5·88 1·00 1·90 10·50 1·66 4·01 3·57 8·60 12·86 6·86 2·12 11·42 1·76 4·51 9·15 3·92

2·15 15·56- 1·66

o

..

. . " :.:;,:..,., . ':: '

'. :

. . . .

207

was

P application (g TSP tree-1)

Early Growth of E. saligna

lower or more negative the index then the more deficient the nutrient relative to the other nutrients. The degree of nutrient balance can be estimated by summing the absolute values of the indices, a larger sum indicating a greater nutrient imbalance.

Effects of fertiliser treatment on height, diameter, periodic increments in height or diameter, nutrient concentration and DRIS indices were assessed by standard analysis of variance procedures using SAS (SAS Institute 1982). Means were separated by Waller-Duncan multiple comparison tests. Correlations between nutrient concentrations or indices and attained sizes or periodic increments were calculated.

Results and Discussion

Response of Individual Trees to Fertiliser Treatments

The height of individual E. saligna trees at 9 months after planting significantly influenced by both the N and P fertilisation, and by the interaction N X P (Fig. 1). Trees increased in height with increasing quantity of P fertiliser, those at the highest dosage being 23% taller than those that received no P fertiliser. The effects ofN fertiliser on 9-month heights, ho:vever, were much greater than the effects ofP fertiliser, the height of trees at the highestN dosage averaging more than three times that of trees receiving no N fertiliser (Fig. 1). In general, the positive effects of both Nand P fertilisers increased with the level of the other nutrient.

The height and diameter of trees at 1'2 months and later were not significantly influenced by P fertilisation. The NXP interaction was significant for height and diameter at 12 and 18 months, but not for the height increment and diameter increment that occurred immediately prior to these measurements (i.e. for 9-12 months and 12-18 months). Thus, the significant NXP interaction on tree size at

3

I 2 . .

IS:SSJ Main effect of P

. .... .................... . ....................-....... _...... ....................._ ...

.......

30 60 90

Fig.!. Height of E. sa ligna trees at 9 months after planting as influenced by the main effects of the phospborus fertilisation (TSP, triple superphospbate) and by the nitrogen fertilisation at the different levels of phosphorus.

208

:. : ... .

R. S. Yost et al.

the 12- and 18-month measurements was essentially a carryover effect of the earlier

differences in 9-month size. Such a lack of response to P was surprising in view of

the low levels of extractable P in the soil at the site, and also the observed responses

by E. saligna to P fertilisers in other Hamakua coast soils (Qureshi 1978). At least

two factors, not necessarily mutually exclusive, may be involved in this failure.

One factor is the high phosphorus retention of the Akaka soil series (Fox and Searle

1978); that is, the amounts of P added may have been altered into unavailable

compounds. A second possibility is that extractable P values for this soil may not

accurately reflect the amounts ofP available to E. saligna root systems, since other

research has demonstrated that eucalypts can utilise relatively insoluble

phosphates (Mullette et al. 1974). Thus, after the trees became established and

mycorrhizal associations had developed, the root systems may have been able to

utilise large amounts of residual phosphate from the repeated applications of P

fertiliser during many years of sugarcane production.

Nitrogen applications, on the other hand, continued to significantly increase height, diameter and their periodic increments through 48 months (Table 2, Fig. 2). The height and diameter to 18 months increased as the N quantity increased. The growth response (i.e. the difference in growth between trees fertilised and not fertilised with N) for all N dosages peaked during the 18-24-month growth period (Fig. 2a). Presumably this peak was associated with the third and final application . , . " ;... .of fertiliser at 15 months. In addition, the height increment during the 18-24-month period was less for the highest N dosage (75 g urea) than for the 50 g dosage (Fig. 2a). The increase in height for the highest N dosage became less in subsequent periods, and by the 36-48-month period was essentially identical with

. ;' ::. ": that of trees receiving no nitrogen. A similar but less extreme pattern occurred with :' '- .' . . . . :..... .the periodic diameter growth (Fig. 2b).

Trees growing without N fertiliser were less than 4 m tall at 48 months-in practice, an unsuccessful crop. Trees with the lowest N treatment (25 g urea) were

" '..

Table 2. Influence of nitrogen fertiliser on height and diameter of . : . , . ' ...E. saligna up to 48 months after planting .f,

":.'

Mean values within columns not sharing a common index letter are significantly different at P=0·05 by the Waller-Duncan mean :. : . ' . ' . ... . .

separation test; LSD is least significant difference

N level Months after planting (g urea tree -I) 9 12 18 24 36 48

(a) Height (m)

0 0·83d 0·83d 1·05d 1·68c 2·89c 3·90c

25 1·59c 1·96e 3·11e 5·79b 7-94b 9·20b

50 2·18b 3·48b 5·17b 9-02a 11·87a 13-60" 75 2·50" 4·27a 6-22a 9·35a 11·42a 12·40"

.

.

LSD 0·18 0·38 . 0·59 0·84 1·24 1·57 .. . .. .

"

0 25

(b) Diameter (em)

0·55e 1·41e

0·87e 2·17e 3-95b 5·07b 2·02e 5·86b

, . . ' .

50 2·58b 4·05b 6·02a 7·36a 8·62a 75 3·33a 4·87a 6·47" 7·49- 8·39a

LSD 0·40 0·42 0·52 0·72 0·89

"

... . .

I

, ------ o · __________ -L __________ __________ __

O 12 _-18----------1-8_L2-4---------2-4 _3-6----------36J --8

Early Growth of E. saligna 209

0·57 I

......r:::Cl'(ji rII 1:- (a)II- 0___ -i

Months after planting

Fig. 2. Influence of nitrogen fertiliser level on periodic increments in (a) height and (b) diameter of E. sa ligna. The bar in each diagram shows the least significant difference at a 0·05 probability level.

more than twice as tall, while the heights and diameters of trees with dosages of 50 and 75 g urea were on average about 40% and 45% greater respectively than those for trees receiving the 25 g urea application. Such substantial differences in tree size plus the rapid drop in growth response soon after the last fertiliser application suggest that the fertiliser regimes (even the highest levels of N and P) were suboptimal, and that repeated applications of fertiliser may be needed to achieve maximum growth in this forest system.

Influence of Nitrogen Dosage on Stand Developmem and Estimated Yield

The effects of N fertiliser on stand development and estimated biomass yield (Table 3) were even greater than those discussed aboye for height and diameter. In part, the greater benefits were associated with the fact that gains in biomass (per tree and per ha) reflected the combined effect of gains in diameter and height. In addition, stand yield (biomass ha -1) was affected by rather substantial differences

210

0·13'

75

0-18 0-08

75

NS

R. S. Yost at al.

Table 3. Influence of nitrogen fertiliser on stand development and estimated yield of E. saligna at 48 months after planting

N level Mean stocking Estimated mean Estimated dry yield (g urea tree-I) (trees ha -I) tree biomass (kg) (tha-1)

0 3266 2-91 9·50

25 4233 9·37 39·66 50 4188 22·5 94·40 75 4277 19·84 84·86

in stocking caused by the effects ofN application on tree survival. The survival at 48 months of trees receiving N fertiliser at 25,50 or 75 g urea was 96%, 95% or 98% respectively, whereas the survival of trees receiving no fertiliser averaged only 76%. Thus, the combined effects ofN dosage on the biomass of individual trees and the stand stocking resulted in estimated yields ranging from 9·5 t ha - t in the no-N treatment to 94· 4 t ha -1 in the 50 g urea treatment (Table 3).

Comparison of yields between N-fertilised plantings and those that received no N fertiliser are perhaps unrealistic because plantings without N fertiliser were, for all practical purposes, failures. However, the estimated yields of the two highest N dosages averaged more than twice the yield of the 25 g urea application, and represented mean annual production rates of about 22 t ha -1. Productivity would undoubtedly have been much higher had additional N fertiliser been applied periodically after the I5-month application.

Table 4. Influence of nitrogen fertiliser on foliar concentrations of macro nutrients in E. saligna at 12-24 months after planting

Mean values within columns not sharing a common index letter are significantly different at P=O·OS by the Waller-Duncan mean separation test; NS, not

significant

N level Macronutrient concentration (%!) (g urea tree-I) N P K ea Mg S

(a) 12 months after plaming a 0-84C 0-13" 0-76d 1-06' 0-31' 0-12"

25 0-69d a-lib 0-S8C 0-84b 0-28b O·OSb

1-16' 0-71e 0-30'b 0·11'50 0-96b

75 1-21" 0-13' 1-03b 0-"" e 0-23e a-II'

LSD 0-10 0·01 0-11 0·07 0-02 0-01

a

25

(b) 18 months after plaming I·SOC 0-19" 1-353 0-74'

2 - 43b 0·20> 1-42" 0-64be 0-24' 0-1ge

O-ISb

0-19b

50 2-94" 0-20> I-lOb 0-S9c 0-1ge 0-21" 2-25b 0-16b O·92e 0-67b 0-21b O-ISb

-LSD 0-03 0-07 0-02 0-02

(e) 24 months after pianrir.g 0 0-98e 0-13b 1·06' 0-82" 0-36' a-Is'

25 I-lObe 0-13b I-11" 0-59b 0-31b 0-13be 50 1·45" 0-16" 1-10> 0-56b 0-16e 0-14·b

1-16b 0-14b 1·08" 0-59b 0-28be 0-12e

LSD 0-14 0-01 0-04 0-03 0-02

4 3

75

50

25 -286c

50 -145b

75

LSD

(c) 24 months afier planting

.,, ', ... .: .

.. '. .. . .

'.','

. .;.,

", .

.

..•./

..

. ' '> .... ,,' , .'-

..: - ... . . ' . .. ;, :

. ......, ..:'... .

. . .

.. ." ..., .....

. " ,' ..c . :•

. . :.

. .. .. : ....

a -288C

Influence of nitrogen fertiliser on DRIS indices of foliar macronutrients inE. saligna at 12-24 months after planting

Mean values within columns not sharing a common letter are significantly different at p= 0·05 by the Waller-Duncan mean separation test; NS, not significant. The 'Sum' tabulated for the DRIS indices is the sum of the absolute values of the indices, which

gives an indication of the degree of nutrient imbalance

la

DRIS indices for macro nutrients p K Ca Mg

(a) 12 months afier planting -7oa -411C 738a 144' -25a -111b 659' 124'

-38a 3a 257b 28b

-41" -2oa 288b -97c

NS 86 114 56

(b) 18 months afier planting 19' 37b 106a

-5a 137a 1·8bc

-19' -89c -77C

-84b -178d 102ab

6' - 30a 31c

-403b

S Sum

57 62 85

-9OC -USb 295"

-25' -13a 90b

-20a -24' 106b

29 44 46

-239' -496c

-234a

79

114' 51b

-52C

15b

52

-112a

-361b

-104a

-131"

98

20C

94b

169a

lO1"b

40

29' -23ab

2,b

-48b

63

1798a

1613a

707b

675b

296

736b

1124a

1194a

1065a

146

921a

468b

290C

328bc

143

a 56c

25 269b

50 420a

295b

59LSD

" a -21()d 25 -80c

42a

-29b

Early Growth of E. saligna 211

Effects of Fertiliser Treatment on Nutrient Concentrations and Indices

Phosphorus applications did not significantly increase foliar P other than for the 9-month sampling (data not shown). Nitrogen fertiliser, however, significantly influenced foliar concentrations of all macronutrients at 9 months, and also affected levels of most macronutrients at 12,18 and 24 months (Table 4). The only

· exception was the potassium concentration at 24 months which was not affected by any fertiliser treatment. At 12 months, concentrations ofN and K were generally enhanced by N fertilisation whereas concentrations of P, Ca, Mg and S were depressed by one or more of the dosages. Nitrogen concentrations at 18 and 24 months increased curvilinearly with N dosage and peaked at the 50 g urea treatment. Calcium and magnesium concentrations in the foliage of fertilised trees (25, 50 and 75 g urea) at 18 and 24 months, however, were significantly lower than in the foliage of unfertilised trees. Nitrogen, phosphorus, potassium, magnesium and sulfur concentrations tended to be higher at 24 months than at 12 months; the highest concentrations for these nutrients, however, occurred in the 18-month samples (collected 3 months after the final fertiliser application). Foliar calcium levels, on the other hand, tended to decrease with tree age. This decline presumably was associated with a progressive decline in availability as the earlier application of CaC03 gradually reacted with the soil and possibly moved below root depth in this

Table 5.

N level

(g urea tree-1) N

75

LSD 45

.,.

212

0·79

24

R. S. Yost et al.

high rainfall area. Such declines in CaC03 availability in this soil have been reported previously by Mahilum et al. (1970).

The DRIS indices of all nutrients and the absolute sum of their indices were significarttly related to N dosage at 12, 18 and 24 months (Table 5). The only exception was P at 12 months. Indices for N and S were generally enhanced with N dosage; the dramatic increases in these indices at 18 months presumably were related to the IS-month fertiliser application. The Nindices were most favourable in the 50 g urea treatment at 18 and 24 months. The P and K indices in the 12- and 24-month samplings also tended to become more favourable with N fertiliser treatment, but they were depressed by N dosage in the samples collected at 18 months. The Ca index was quite high in the 12-month sample, reflecting the recent application of crushed coral, but it then decreased to lower levels in subsequent samplings. The Mg index was rather low for the 18-month samples. Apparently the recent fertiliser application created an imbalance among several nutrients as indicated by the high values of the overall sum.

Comparison of Nutrient Concentrations and DRlS Indices

The data discussed in the previous sections demonstrated that growth, nutrient concentrations and DRIS indices' were all affected by N fertiliser treatments. Moreover, the concentrations and indices of nutrients other than those applied in the fertiliser treatment were altered. In this section, we examine the usefulness of the two methods (concentration and DRIS index) for assessing nutrient status.

One important consideration is the degree to which the measured nutrient status is correlated with past growth (as indicated by the attained size at the time the foliar sample was taken or the immediate past increment if size was measured periodically) and with future growth. Correlations between size or growth and nitrogen (as gauged by percentage nutrient concentration or DRIS) were higher

Table 6. Correlation coefficients between nutrient concentrations or DRIS indices and past or future growth of E. saligna

The results compare the correlation coefficients between percentage nutrient concentrations (NC%) or DRIS indices and attained tree height, immediate past increment in height or. future increment for both nitrogen and phosphorus

status

Tree age Correlation coefficients r (months) Tree height Past increment Future increment

NCOAI DRIS NCOAI DRIS NC% DRlS

(a) Nitrogen

9 0·82 0·65 0·91 0·74

. ... . . • >

12 0·67 0·77 0·75 0·65 0·73

18 0·38 0·57 0·42 0·60 0·71 0·82

24 0·64 0·82 0·71 0·84 0·76 0·67 .. : . :

9

12

18

0·76

0·37

-0·19

(b) Phosphorus

0·53

0·21 0·45 0·15

-0·38 -0·13 -0·36

o·n 0·35

0·14

0·41

0·18

-0·11

-.'" ':'."

-':.': ..

. : " .... :.-'

.

0·42 0·53 0·52 0·55 0·74 0·33

- -

213 , ' . ":,

- .. . ," , " .; ... .

' ' ' .. , :

•1':,.'." ,.

.... " " " "

Early Growth of E. saligna

than those for measures of phosphorus status (Table 6). This finding was expected becauseN increased tree growth more than P. At 9 months, concentrations were more highly correlated than DRIS indices with size and past or future growth. At 12, 18 and 24 months, however, the DRIS indices for nitrogen were more strongly related to size and past growth than were the concentrations. Future increments at 24 months (growth 24-48 months) were more strongly related to the concentrations than to the D RIS indices.

In general, nutrient concentrations alone were as useful in this study as the DRIS indices. Thus, because the derivation of a DRIS index requires more data and rather complex calculations, there is little reason to recommend it to Eucalyptus plantation managers at this time. The possibility remains, however, that the advantages and potential of the DRIS approach might be realised in other situations and/or in applications involving a wider range of soil and site conditions, growth-limiting factors and management treatments.

Acknowledgments

We thank the Department of Energy for a portion of the funds required to conduct and report this research. We also would like to thank the field technicians of the Bioenergy Development Corporation for their assistance in measuring and collecting the growth data as well as for collecting the tissue samples. The tissue samples were analysed by the University of Hawaii Agricultural Diagnostic Service Center, and soils were analysed by the technicians at the Brewer Chemical Laboratory .

References

Beaufils, E. R. (1973). Diagnosis and recommendation system (DRIS). Soil Sci. Bull. No.1, Dep. Soil Sci. and Agro-MeteoroL, Univ. NataL Pietennaritzburg, S. Africa.

Cremer, K. W., Cromer, R. N., and Flore:Jce. R. G. (1978). Stand establishment. In'Eucalypts for Wood Production' (Eds W. E. Hillis and A. G. Brown), pp. 81-135 (CSIRO Aust.: Melbourne).

Cromer, R. N. (1971). Fertilizer trials in :'oung plantations of eucalypts . ..lust. For. Res. 5, 1-10.

Fox, R. L., and Searle, P. G. E. (1978). Phosphate sorption by soils of the tropics. In'Diyersity of Soils of

the Tropics', pp. 97-119, Soil Sci. Soc. Am. Special Pub!. No. 34. Mahilum, B., Fox, R. L., and Silva, J. A. (1970). Residual effects of liming volcanic ash soils in the

humid tropics. Soil Sci. 109, 102-9. Miyasaka, S. C. (1984). Comparison of quick- and slow-release fertilizers in young plantings of

Eucalyptus spears. Tree Plamers' Sores 35, 20-t Muilette, K. 1., Hannon,)L Land EIIiotL . .1.. G. L. (1974). Insoluble phosphorus usage by Eucalyptus.

Plant Soil 41, 199-205. Qureshi, A. H. (1978). Diagnosis of nutri:ional disorders in EucalYPllIs saligna sm. seedlings and their

responses to fertilization in forest soils. Dissertation Abstracts International No. 7820436. SAS Institute (1982). 'SAS User's Guide: Statistics', 1982 edn (SAS Inst.: Cary, \"C). Schonau, A. P. G. (1983). The effects of :e:-ilizing on :he foliar nutrient concentrations in ElIcaiypl!ls

grandis. Fert. Res. 2. 73-S7. Schubert, T. H., and Whitesell. C. D. (lSS5). Species trials for biomass plantations in Hawaii: a first

appraisal. USDA For. Sc:-,:. Res. P1p. \"0. PSW-l 76. Sumner, M. E. (1977). Use of the DRIS 5:-';le:71 in foliar diagnosis of crops at high yield levels. Commull.

Soil Sci. Plant Analysis 8. 251-68. Truog, E. (1930). The determination of:o.= e::dily available phosphorus of soils. 1. Am. Soc. Agroll. 22,

874.

Walters, G. A. (1973). Gro\v1h of E:ic !::P[:LS saligna-a spacing study after ten years. f. Far. 71, 346-8.

214 R. S. Yost et al.

'f' •. '.' .. , ':" ,

,';: .

," :' .. , ; ';. " ": .. :':, .: .. -,"

':.' .

.'

Ward, S. c., Pickersgill, G. E., Michaelsen. D. V., and Bell, D. T. (l985). Responses to factorial combinations of nitrogen, phosphorus and potasSium fertilizers by saplings of Eucalyptus saligna Sm., and the prediction of the responses by DRIS indices. Aust. For. Res. 15, 27-32.

Manuscript received 21 August 1986. accepted 7 September 1987