Phosphorus fertiliser placement and seedling success in Australian jarrah forest

Phosphorus Fertiliser Placement and Seedling Success in Australian Jarrah Forest

S.J. George Centre for Land Rehabilitation, The University of Western Australia, Australia

M. Tibbett Centre for Land Rehabilitation, The University of Western Australia, Australia

M.F. Braimbridge Centre for Land Rehabilitation, The University of Western Australia, Australia

S.G. Davis Centre for Land Rehabilitation, The University of Western Australia, Australia

S. Vlahos Worsley Alumina Pty Ltd, Australia

M. Ryan School of Plant Biology, The University of Western Australia, Australia

1 INTRODUCTION Natural re-colonisation following surface-mining is often slow and typically requires intervention if the re-establishment of a self-sustaining ecosystem integrated with the surrounding landscape is desired in human timescales. Current rehabilitation practices include an initial application of mineral fertilizer, especially phosphorus, to facilitate good seedling establishment and early ground cover. However, limited evidence suggests long-term effect of an over supply of P may result in disrupted nutrient cycling and the long-term exclusion of P sensitive species. South-west Australian jarrah forests are adapted to inherently low-phosphorus soils due to evolving from low P parent material and subsequent leaching of phosphate. As a result this type of ecosystem has a ‘tight cycle’ of internal redistribution of P in mature ecosystems. The agreed rehabilitation prescription involves ‘scarification’ (soil ripping to a depth of 30-40 cm during January to May) followed by broadcast seeding within 4 days. In August superphosphate (with Cu, Mo Zn) is applied by helicopter. A change from aerial application of fertiliser to a ground-based application at the time of scarification was proposed. To assess the impact of a P fertilizer placement (top-dressed or incorporated) and time of fertilisation (summer, autumn and winter), a large-scale field-trial was established in early 2004 in a post-mined area of Worsley Alumina’s Boddington Bauxite Mine (BBM), Western Australia. This paper evaluates the impact of these treatments on establishment and key growth characteristics of four northern jarrah forest species following the first growing season after field-trial establishment.

2 METHODOLOGY

2.1 Research Site To study effects of ground-based phosphorus fertiliser application (placement and time) a trial was established between April-August 2004 at the BBM (32o 50’S, 116o 30’ E). BBM is evaluating the potential to change its air-borne fertiliser application to a ground-based practice. The two post-mined pits selected had been cleared of native jarrah forest vegetation and surface-mined prior to the commencement of the experiment. The pits were shaped to reflect the surrounding landscape and the entire area was deep-ripped to loosen underlying clays and contoured to integrate into the surrounding forest landscape. The overburden was then replaced followed by the topsoil which was directly returned from nearby pit.

2.2 Field Trial Layout The phosphorus fertilizer used for the trial was single super phosphate containing: 9.1 g kg-1 total P (equivalent by weight to 40.95 kg ha-1 P), 10.1 g kg-1 S, 9.0 g kg-1 Ca, 0.6 g kg-1 Cu, 0.3 g kg-1 Zn and 0.06 g kg-1 Mo. Seven treatments were incorporated into an incomplete randomised block design (replicated four times, except control treatments which was replicated only twice; Table 1). Treatment plots (25 × 25 m) were randomised with two main classes of treatments of: 1) placement of fertiliser application (top-dressed or

Mine Closure 2006 ― Andy Fourie and Mark Tibbett (eds)© 2006 Australian Centre for Geomechanics, Perth, ISBN 0-9756756-6-4

incorporated) and, 2) timing of fertiliser application (summer, autumn, winter). A standard rehabilitation seed mix comprising understorey and tree species) was broadcasted.

Table 1 Treatment structure based on placement (top-dressed or incorporated) and time of application (summer, autumn and winter) of single super phosphate

Fertiliser placement

Fertiliser application time* Scarification & seeding*

1 Top-dressed Winter Summer 2 Top-dressed Winter Autumn 3 Top-dressed Summer Summer 4 Top-dressed Autumn Autumn 5 Incorporated Summer Summer 6 Incorporated Autumn Autumn

Control - - Autumn & Summer *‘Summer’: 19th April 2004, ‘Autumn’: 13th May 2004, ‘Winter’: 26th August 2004

2.3 Field Sampling and Analyses Four species: Acacia celastrifolia (pioneer legume), Eucalyptus marginata (keystone tree species), Bossiaea ornata (common legume shrub), and Hakea undulata (common under-storey non-legume shrub) found in northern jarrah forest) were assessed during May 2005. Seedling biomass of the selected species was estimated based on a non-destructive method (the Adelaide technique; Maywald et al. 1998) and Colwell (1963) extractable soil P was determined at both ridges and furrows formed following deep-ripping of the soil at 0-5, 5-10, 10-20 and 20-30cm.

2.4 Glasshouse Trial To investigate the impact of P fertiliser placement and rate on the very early growth of four selected species (A. celastrifolia, E. marginata, B. ornata, and H. undulata), a full-factorial designed glasshouse trial was undertaken. The impact of top-dressing (applied to top 2 cm of the soil) versus incorporation (throughout the whole depth of soil) on species shoot and root biomass when high (P equivalent to 450 kg ha-1 of super phosphate) and low rates of P (P equivalent at 150 kg ha-1 of super phosphate) were applied. The soil used in the trial was direct-returned topsoil from the mine. Eight scarified seeds per pot per species were sown approximately 5 mm into the soil and were thinned to one plant after 10 weeks. The seedlings were harvested after 10 weeks. Each pot was split open and the top 2 cm of the profile was removed and washed to obtain the roots and above ground shoot material. The remaining 10 cm of the soil core was washed and root material removed. The seedling root and shoot biomass were assessed.

2.5 Statistical Analysis An unbalanced incomplete block design analysis of variance (ANOVA) was carried using GenStat™ version 7.2 (www.vsn-intl.com) to determine the significance of treatment effects and interactions on legume and non- legume densities, selected species density, biomass estimations and P concentrations (foliar and soil extractable) for the field trial. A factorial ANOVA was carried out on glasshouse pot trial measurements (root and shoot biomass and various ratios).

3 RESULTS

3.1 Legume and Non-legume Densities In the first year following initiation of the field trials, legumes (Acacia celastrifolia) to non-legumes (Eucalyptus marginata, Bossiaea ornata, and Hakea undulata) seedling density across time of fertilisation, placement of P fertiliser showed no significant difference (P<0.05) between top-dressed P to incorporated (Fig 1). However, summer application of P fertiliser, irrespective of placement method, showed significantly lower (P<0.02) legume : non-legume ratio compared to winter or autumn application (Table 2).

Phosphorus Fertiliser Placement and Seedling Success in Australian Jarrah Forest S.J. George, et al.

http://www.vsn-intl.com/

Table 2 Effect of single super phosphate fertiliser placement and timing on the ratio of legume to non – legume density


Fertiliser application time

Scarification & seeding Ratio

1 Top-dressed Winter Summer 4.140 2 Top-dressed Winter Autumn 3.869 3 Top-dressed Summer Summer 2.914 4 Top-dressed Autumn Autumn 4.501 5 Incorporated Summer Summer 2.700 6 Incorporated Autumn Autumn 5.212

Control - - Autumn & Summer 3.723 LSD 1.590* 1 Incorporated 3.980 2 Top-dressed 3.881

Control -

2.941 LSD N.S.

1 Summer 2.765 2 Autumn 4.814 3 Winter 3.963

Control

- 3.767 *P<0.05, ** P<0.02 and N.S. not significant at P<0.05 LSD 1.272**

3.2 Species Plant Density and Biomass

3.2.1 Seedling density Acacia celastrifolia and B. ornata were the most abundant of the selected species (Figure 1) while E. marginata and H. undulata were the least abundant (data not shown). The impact of placement and time of fertiliser application on seedling density differed between A. celastrifolia and B. ornata. A. celastrifolia had a higher density under all treatments compared to B. ornata, except for control (no fertiliser applied) where this trend was reversed (Figure 1). Across all fertilised treatments E. marginata had a higher plant density than H. undulata (data not shown).

3.2.2 Seedling biomass There was a significant impact on the seedling biomass by fertiliser incorporation compared to top-dressing while timing of fertilisation did not show any difference in biomass, with summer, autumn and winter application all having a higher biomass than the unfertilised control (P<0.05) (Table 3). At a species level, A. celastrifolia biomass showed a larger biomass while the remaining species had having lower biomass (Table 3). The method of application impacted differently on the selected species. Acacia celastrifolia biomass was significantly larger when fertiliser was incorporated, and lowest when no fertiliser was applied (P<0.05) (Table 4). Interestingly, both fertiliser placement and timing did not affect the remaining three species studied. The biomass values for H. undulata were excluded from the seedling biomass analysis due to low seedling density for testing statistical significance.

3.2.3 Soil P nutrient status Colwell extractable P fraction, which represents the labile plant available P fraction, was higher in the furrows (Figure 2) compared to the ridges formed following scarification. Colwell extractable P concentration at 0-5 cm depth was significantly higher for the top-dressed fertiliser placement to soil incorporated at various times (autumn, winter and summer). The control and natural forest soil also had significantly lower P compared to top-dressed soil at 0-5 cm depth. The ridge had similar extractable P concentration at both P fertiliser placement but was significantly higher than control and natural forest. As expected, down the soil profile P fertiliser incorporation treatment showed a more uniform distribution to top-dressed P placement.

Ecosystem Reconstruction and Pedogenesis

SUMMER AUTUMN WINTER No fertiliser application

Figure 1 Mean densities of A. celastrifolia ■ and B. ornate □ changes following single super phosphate fertiliser placement (top-dressed (TD), incorporated (I) and not applied) and timing of fertilisation (summer, autumn, winter and not applied)

Table 3 Estimated seedling biomass (g m-2) changes for selected species with placement of P fertiliser application and time of application. (Note: H. undulata biomass values excluded).


Fertiliser application

time

Scarification & seeding

A. celastrifolia

B. ornata

E. marginata

1 Top-dressed Winter Summer 19.1 0.141 0.205 2 Top-dressed Winter Autumn 27.7 0.259 0.149 3 Top-dressed Summer Summer 30.1 0.094 0.543 4 Top-dressed Autumn Autumn 43.4 0.284 0.205 5 Incorporated Summer Summer 109.8 0.153 1.374 6 Incorporated Autumn Autumn 139.5 0.135 0.126

Control - - Autumn & Summer 34.2 0.187 0.296

LSD 80.5* N.S. N.S. 1 Incorporated 124.7 0.144 0.750 2 Top-dressed 30.0 0.195 0.276

Control -

34.2 0.187 0.333 LSD 57.6*** N.S. N.S.

1 Summer 69.9 0.124 0.959 2 Autumn 91.4 0.210 0.165 3 Winter 23.4 0.200 0.177

Control

- 34.2 0.187 0.333 *P<0.05, *** P<0.01 and N.S. not

significant at P<0.05 LSD N.S. N.S. N.S.

Den

sity

(pla

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Time of fertiliser application

TD TD TD

SUMMER AUTUMN SUMMER

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SUMMER

CONTROL I I TD

Scarification & seeding AUTUMN


Col

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furr

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Time of fertiliser application Scarification & seeding


TD TD TD CONTROL I I TD NATURAL FOREST

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WINTER No fertiliser application

SUMMER AUTUMN SUMMER AUTUMN &

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Colwell extractable soil P (mg L-1)

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Colwell extractable soil P (mg L-1)

0 10 20 0 20 0 10 20 10 2010 200 10 20 0 10 20 0 10 20

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20-

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No fertiliser application

Time of fertiliser application

SUMMER AUTUMN SUMMER AUTUMN &

SUMMER

AUTUMN

Scarification & seeding

AUTUMN

LSD***

Figure 2 Collwell extractable soil phosphate comparisons between fertilizer placement (incorporated (I) and top-dressed (TD)) and timing in furrows ■ and ridges □ (formed following deep ripping) (*** P<0.01)


3.3 Glasshouse Study Application of P fertiliser to the top 0-2 cm (top-dressed) and to the whole 10 cm soil profile (incorporation), E. marginata produced significantly larger root biomass when P was incorporated at lower levels (Table 4). However, no such differences were observed in the case of A. celastrifolia and H. undulata. Total root biomass and shoot biomass did not differ when fertiliser was top-dressed or incorporated into the soil profile (Table 4). However the glasshouse trial showed no evidence of larger seedling biomass following incorporation of P fertiliser as opposed to top-dressing across treatments, High and low rates of P incorporated into the soil did not significantly impact shoot biomass of the selected species (P>0.05). The shoot biomass did however differ for each species with E. marginata having a higher shoot biomass than H. undulata and A. celastrifolia. Top-dressed and incorporated P fertiliser at high and low rates had no significant effect on seedling root:shoot ratios (P>0.05). The B. ornata treatments were excluded from the glasshouse trial analysis as there were few emergences for testing statistical significance.

Table 4 Effects of P fertilisation rates (high rate – equivalent to 450 kg P ha-1 and low rates - 150 kg P ha-1 of super phosphate) and placement (top-dressed and incorporated) on juvenile seedling shoot and root biomass (mg) in the glasshouse trial

High Low Species Incorporated Top-dressed Incorporate Top-dressed

A. celastrifolia 27.3 21.3 21.1 21.0 E. marginata 79.0 58.6 75.2 89.3 Shoot

Biomass H. undulata 31.8 17.0 47.8 24.1

L.S.D. – 34.2*** A. celastrifolia 9.0 14.3 12.3 12.7 E. marginata 34.5 39.1 57.2 35.7 Root

Biomass H. undulata 22.0 10.5 26.2 14.0

L.S.D. – 18.9*** A. celastrifolia 4.0 5.0 3.1 3.7 E. marginata 12.7 9.2 3.7 7.5

Root Biomass (0-2 cm) H. undulata 6.1 3.2 5.1 7.5

L.S.D. - 5.4* A. celastrifolia 5 9.3 9.2 9 E. marginata 21.7 29.9 53.5 28.3

Root Biomass (2-10 cm) H. undulata 15.8 7.2 21.1 6.5

L.S.D. - 17.2*** A. celastrifolia 0.339 0.666 0.638 1.138 E. marginata 0.665 0.833 0.804 0.557 Root biomass:

Shoot biomass H. undulata 0.922 0.696 0.645 0.436

L.S.D. - NS A. celastrifolia 3.6 2.4 7.0 7.3 E. marginata 1.7 3.7 15.5 3.7

Root (2-10 cm) : Root (0-2 cm)

biomass H. undulata 4.1 2.5 6.5 1.3 *P<0.05, *** P<0.01 and N.S. not significant at P<0.05 L.S.D. - 7.2*

4 DISCUSSION This study was initiated mainly to assess the potential consequences of a proposed shift of fertilizer delivery to post-mined rehabilitation areas by Worsely Alumina Pyt. Ltd. (WAPL) from an aerial to a ground-based application. Ground-based fertiliser application opens the opportunity for increased manipulation of fertilizer delivery hence treatment options like placement and timing were investigated in this study. The premise of the study was to determine which aspects of P fertiliser application need to be considered for early jarrah


forest reconstruction? The study examined whether phosphorus fertiliser placement at different seasons affected the establishment of native jarrah forest seedlings after one growing season. Phosphorus fertilisation and hence plant availability (as determined by Colwell extractable soil P) had a strong effect on the plant community (legume vs non-legumes). The season of application had a less pronounced effect.

4.1 Importance of Fertiliser Placement on Selected Jarrah Seedling Establishment

Based on the two P fertiliser placement strategies evaluated, seedling biomass for A. celastrifolia, (a northern jarrah forest pioneer species) significantly improved from incorporation opposed to top-dressing in soil in the field trial. Seedling biomass of E. marginata (a climax species) showed a non-significant trend favouring P fertiliser incorporation over top-dressing while B. ornata (commonly occurring jarrah forest shrub) showed no clear trend at this early growth stage. The inherent variation associated with large-scale field trials should also be taken into consideration when evaluating the field trial results. A reason for better performance of A. celastrifolia may be due to roots better exploring a larger soil volume cross-section, an inherent trait attributed to early-successional growth strategy of pioneer species (Tyree et al. 1998). Phosphorus in soil is rapidly adsorbed by iron and aluminium atoms exposed at the edges of iron and aluminium oxides (Mengel and Kirkby, 1998 and Marschner, 1986). This behaviour restricts the mobility of soil P resulting in creation of locally concentrated zones as evident from the significant variation in Colwell extractable P between incorporated and top-dressed P placement (Figure 2). Incorporating P into the soil increases the opportunity of P being adsorption onto less saturated sites than those on the soil surface and as a result P becomes generally less available fixed deeper in the profile (Bolland and Gilkes, 1998). This effect was expected to be heightened on these revegetated laterite soils as the soil matrix contains high amounts of iron and aluminium oxides (Moore 1998). There is some evidence that local proliferation of surface lateral roots may achieve significantly greater exploitation of less mobile nutrients such as P (Robinson, 1996). This can be seen as an adaptive mechanism whereby root systems increases their surface area to acquire nutrients delivered by diffusion (main driving force for the movement of P and K) to the root surface Marschner (1986).

The glasshouse study was carried out to further investigate the ability of the selected jarrah forest species to access spatially segregated (top-dressed and incorporated) P nutrient sources. Glasshouse experiment reveals the contrasting phosphorus exploration strategies of E. marginata (with known ability for symbiotic mycorrhizal association), A. celastrifolia (a N-fixing species) and H. undulata (Proteaceace species with ability for forming cluster roots). E. marginata produced significantly larger root biomass when P was incorporated and at lower levels (Table 4) most of the roots were in the 2-10 cm depth zone. However, no such differences were observed in the case of A. celastrifolia and H. undulata. These findings are in concurrence with Drew (1975) and Van Vuuren et al. (1995) studies in which effect of non-uniform nutrient placement triggered the roots to grow preferentially in regions of soil containing favourable nutrient concentrations. Furthermore, Drew (1975) suggests that manipulation of root proliferation by fertiliser incorporation can assist in the long term establishment of selected species. This has a special relevance in rehabilitation context since development of deep and evenly distributed seedling root system at an early stage aids in better overcoming drought prone and nutrient deficient conditions.

The glasshouse trial showed no evidence of larger seedling biomass following incorporation of P fertiliser as opposed to top-dressing across treatments, which may be because more energy being partitioned into root growth as opposed to shoot at this early stage. This is an adaptation for survival in nutrient deficient environments (Handreck, 1997), particularly for jarrah forest species. In order to ensure the survival and long-term establishment of jarrah species due to constant fire and drought disturbance cycle, the jarrah has a conservative growth strategy whereby it limits the above ground growth until it has developed an adequate root system (Dell and Havel (1989). The fact that the root: shoot ratio was lower under most of the treatments for the higher rate of P application, in the current study similar to findings by Hendreck (1997) who also observed that high rates of P fertiliser application can be detrimental to the root growth of eucalypt seedlings.

Summer, autumn, winter and unfertilised control application had no significant effect on the seedling density and biomass. Although there is only anecdotal evidence on influence of time of fertilizer application and ensuing effect on seedling establishment, Lockley and Koch (1996) found that summer fertiliser application increased jarrah seedling density compared to fertilisation in winter. Although the current study did not


investigate spring fertilisation, studies have observed higher growth rate for jarrah, marri and certain understorey species occurred with spring fertilisation (Humphrys, 1987; Matysiak, 1988 and Rohl 1988).

4.2 Dominance of Acacia Celastrifolia as a Management Issue Acacia celastrifolia dominated the rehabilitated areas after one season of growth, regardless of treatment, which is an important management issue. One of the most important findings from a rehabilitation management perspective was this dominance of A. celastrifolia over other selected species. For this reason primarily A. celastrifolia was discontinued from the seed mix by BBM. These seedlings were derived from the soil seed bank. Glossop (1981) and Koch and Davies (1993) reported higher seed-bank diversity associated with the double-and direct returned topsoil handling procedure, Koch et al.,. (1995) suggested that changing the topsoil handling would mainly reduce small-seeded species and not large seeded like acacia seeds. Assessing the impact of tall dense Acacia understorey on small native shrubs and herb species, Koch and Davies (1993) observed a shift towards dense understorey of legumes, predominately Acacia spp. displacing smaller species during initial rehabilitation establishment stage. Their study concluded that following senescence of this pioneering legume species may bring the succession to smaller shrub and tree species (Koch and Davies, 1993). For the current study, treatments with lower fertiliser rates showed a reduction in density and biomass of A. celastrifolia. This could be a factor in the increase in B. ornata density when fertiliser was not applied. The above findings suggested that applying no fertiliser may be a practice that will reduce the density and biomass of A. celastrifolia and potentially increase species diversity. However this suggestion is based on 2 species of approximately nearly 800 native species (Bell and Heddle, 1989) of the northern jarrah forest. Therefore, further research efforts should be directed into creating a best management practice for the reduction in the dominance of A. celastrifolia in rehabilitated areas.

5 CONCLUSIONS This study has shown that a number of factors influence the early establishment of native seedlings in post bauxite mined rehabilitated areas. It is important for rehabilitation purposes to practice an efficient fertiliser application system. The placement of phosphorus fertiliser was a more important factor than timing of application on affecting seedling growth and establishment. The current trial suggests that incorporating fertiliser is important in the establishment of the selected species. Incorporation of fertiliser produces larger biomass and has the potential to promote seedling establishment by developing an evenly proliferated root system. The glasshouse trial provided evidence to be considered for reduction of fertiliser applied from the currently applied levels. Therefore based on the results of this study future field trials should assess the effects of variations in the rate of single superphosphate on the establishment of native jarrah forest seedlings.

ACKNOWLEDGEMENTS Thanks to Worsley Alumina Pty Ltd for funding the study. Many thanks to Michael Smirk (UWA) for laboratory assistance, Russel Beazley and Trudy Worthington (UWA) for their help in collecting field samples, Claire Reid, Ben Seaborn and Haakon Nielssen (BBM) with logistic support, Mattiske Consulting Pty Ltd with floral survey and Prof. Bob Gilkes (UWA) for help with the field experimental design.

REFERENCES Bell, D.T. and Heddle, E.M. (1989) Floristic, morphological and vegetational diversity. In: The Jarrah Forest – A

Complex Mediterranean Ecosystem, B. Dell, J.J. Havel and N. Malajcuk (eds), Kluwer, Dordecht.

Bolland, M.D.A. and Gilkes, R.J. (1998) The relative effectiveness of superphosphate and rock phosphate for soils where vertical and lateral leaching of phosphate occurs. Nutrient Cycling in Agroecosystems. 51, pp. 139-153.

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Dell, B. and Havel, J.J. (1989) The Jarrah Forest, an introduction. In: The Jarrah Forest – A Complex Mediterranean Ecosystem, B. Dell, J.J. Havel and N. Malajcuk (eds), Kluwer, Dordecht.


Drew, M.C. (1975) Comparison of the effects of a localized supply of phosphate, nitrate, ammonium and potassium on the growth of the seminal root system, and the shoot in Barley. New Phytologist 75, pp. 479-490.

Glossop, B.L. (1981) Assessment of the floral composition achieved by two topsoil handling techniques used for rehabilitation of bauxite mined areas. Alcoa of Australia Ltd. Environmental Research Bulletin 11, Booragoon, Western Australia.

Handreck, K.A. (1997) Phosphorus requrements of Australian native plants. Australian Journal of Soil Research. 35, pp. 241-289.

Humphrys, H. (1987) An assessment of fertiliser requirements of seeded understorey species of a jarrah forest on a rehabilitated, bauxite mined pit. Applied Mini Project. Curtin University of Technology, Western Australia.

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Lockley, I.R. and Koch, J.M. (1996) Response of two eucalypt species to fertilizer application on rehabilitated bauxite mines in Western Australia. Pinjarra, W.A., Alcoa of Australia Ltd. Environmental Research Bulletin 27, Booragoon, Western Australia.

Marshner, H. (1986) Mineral Nutrition of Higher Plants. Academic Press, New York.

Matysiak, A. (1988) The influence of fertiliser type, rate and time upon mean height and number of Eucalyptus marginata. Applied Biology Mini Project. Curtin University of Technology. Western Australia.

Maywald, D., McArthur, E.D., Jorgensen, G.L., Stevens, R. and Walker, S.C. (1998) Experimental evidence for sex-based palatability variation in flowering saltbush. Journal of Rangeland Management. 51, pp. 650-654.

Mengel, K. and Kirby, E.A. (1998) Principles of Plant Nutrition. 5th Ed. Kluwer Academic Publishers, Dordecht.

Moore, G. (1998) Distinctive morphological features and their agricultural significance. In: Soil Guide. A Handbook for Understanding and Managing Agriculutral Soils. (Ed. G. Moore). Agriculture Western Australia, Bulletin No. 4343.

Robinson, D. (1996) Resource Capture by Localized Root Proliferation: Why Do Plants Bother? Annals of Botany 77, pp. 179-185.

Rohl, L. (1988) Fertiliser requirements for the establishment of Marri and Blackbutt by seed in rehabilitated bauxite mines. Applied Biology Mini Project. Curtin University of Technology. Western Australia.

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Van Vuuren, M.M.I., Robinson, D. and Griffiths, B.S. (1996) Nutrient inflow and root proliferation during the exploitation of a temporally and spatially discrete source of nitrogen in soil. Plant and Soil 178, pp. 185-192.


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Phosphorus fertiliser placement and seedling success in Australian jarrah forest