HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ringrose, C. Articles by Neilsen, W. A. Search for Related Content PubMed Articles by Ringrose, C. Articles by Neilsen, W. A. Agricola Articles by Ringrose, C. Articles by Neilsen, W. A. Related Collections Soil Fertility and Productivity Frozen Soils Nitrogen

Forest, Range & Wildland Soils

Growth Response of Eucalyptus regnans and Soil Changes following Periodic Fertilization

^a Forestry Tasmania, 79 Melville Street, Hobart, Tasmania, 7000, Australia
^b Cooperative Research Centre for Sustainable Production Forestry, GPO Box 252-12, Hobart 7001 Australia

^* Corresponding author (carolyn.ringrose{at}forestrytas.com.au)

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Increased demand for plantation hardwood production has resulted in the progression of Eucalyptus plantations onto soils of reasonable physical structure but low nutrient status. This study was undertaken to investigate the effects of periodic fertilization through 15 yr on stand growth and soil chemistry of a Eucalyptus regnans F. Mueller plantation on a high rainfall site in southern Tasmania. Substantial response to N fertilizer, applied as ammonium sulfate, were measured, but there was no response to P applied as single superphosphate, either alone or in combination with N. Annual applications of N fertilizer, for a period of 13 yr, at 100 kg N ha^–1 yr^–1 doubled volume growth from 125 to 281 m³ ha^–1, at Age 19 yr. Long-term fertilization resulted in the accumulation of nutrients within the forest floor and surface soils. Significant reductions in soil pH, from 4.5 to 3.6 in the surface soil, were associated with the highest rate of fertilization. Reductions in pH occurred with both nitrogenous and phosphatic fertilizers. Substantial reductions in exchangeable Mg concentrations in surface soils, from 258 to 71 mg kg^–1 were also measured. The research highlights the balance needed between obtaining growth response and causing detrimental soil effects from long-term fertilization.

Abbreviations: N2Y, ammonium sulfate applied every second year • NIL, nil treatment • P1YN1Y, superphosphate and ammonium sulfate applied annually • P2Y, superphosphate applied every second year • P2YN2Y, superphosphate and ammonium sulfate applied every second year • P4YN4Y, superphosphate and ammonium sulfate applied every fourth year • PAI, periodic annual increment

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
LARGE AREAS OF NATIVE HARDWOOD forest are being reserved from commercial use (IUCN, 1992) and eucalypt plantations are being developed to provide a proportion of the world's hardwood resource. This increased demand for plantation wood production, on a base of decreasing land availability, has resulted in the progression of plantations onto soils of reasonable physical structure but low nutrient status. This trend is combined with increasing demands for faster growth and greater product utilization from forest sites, intensifying nutrient demand, and removal. Fertilizer applications of N and P at planting can substantially increase early growth and survival (Judd et al., 1996; Neilsen, 1996). To continue growth responses on infertile soil, over the length of the rotation, long-term N fertilization is required.

In stands of P. radiata, single or infrequent P fertilizations have produced prolonged growth responses (Gentle et al., 1965; Neilsen et al., 1984). However, frequent periodic N fertilizer additions were required to maintain stand growth when N was limiting (Ringrose and Neilsen, 2005). Application of 100 kg N ha^–1 every fourth year was sufficient to maintain growth. However, the Haplohumult soil used in that experiment had very low nutrient reserves. Continued fertilization during a period of 13 yr significantly reduced soil pH and exchangeable Mg and Ca contents (Ringrose and Neilsen, 2005).

Following canopy development, internal redistribution and nutrient return from decomposition become critical processes in supplying nutrients for new growth (Weston, 2001). The forest floor is important in storing nutrients and buffering nutrient fluxes in native eucalypt forests (Attiwill and Leeper, 1987). In the northern hemisphere, Tamm and Popovic (1995) noted the importance of forest floor organic matter in the retention of base cations within forest systems, and the role of forest floor maintenance in planning management systems for fertilization.

Foliar nutrient concentrations have been considered as a useful indicator of tree health for eucalypt species (Ballard and Will, 1978; Dell et al., 2002). Dell et al. (2002) determined deficiency and adequate nutrient concentrations for some Eucalypt species in young plantations, linking nutrient deficiency levels to symptoms of poor health. However, the usefulness of foliar nutrient concentrations in predicting growth responses, particularly in older trees, is less clear (Judd et al., 1996; Neilsen, 1996). In a 7.5-yr-old fertilizer experiment, in E. regnans and E. nitens, Neilsen (1996) found no relationship between foliar N or P concentrations at that age and growth.

This experiment was established to study the response of a eucalypt plantation to various periodic applications of later age N and P fertilization. Changes in the soil profile and chemistry due to fertilization, were determined. Foliar nutrient contents were also examined periodically to compare treatment effects and growth response.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
A field experiment was established in a 5-yr-old E. regnans plantation in southern Tasmania (43°17' S lat., 146°54' E long.), to evaluate later age fertilization with N and P, applied periodically, in combination, and alone.

The topography of the experimental site was undulating, generally with a south-easterly slope of about 10% and an altitude of 100 m. Understorey was moderately dense bracken fern [Pteridium esculentum (Forst. f.)] with some Cassinia aculeata (Labill.) R.Br. and Acacia verticillata (L'Herit.) Willd. Originally the site carried Eucalyptus obliqua L'Herit. of 34 to 41 m height. The soil is a Hapludalf formed on Jurassic dolerite, with a total soil depth of 0.9 to 1.0 m. The site had been logged and burned in wild fires before plantation establishment, resulting in only about 10 cm of top soil remaining (compared with about 15 cm in adjacent native forest [Grant et al., 1995]). The soil has clay-loam texture, but is medium to low in nutrient reserves. Average annual rainfall was 1200 mm. The initial plantation stocking was 1333 stems per hectare (SPH) at a spacing of 3 by 2.5 m.

The fertilizer experiment was designed for analysis as a N and P factorial because of the lack of long-term data for eucalypt stands, with applications every second year of N only (N2Y), P only (P2Y), and N and P together (P2YN2Y) as well as a nil treatment (NIL). In addition, a fertilizer level experiment was designed with regular applications of N and P together, with the amounts set by the period between applications. There were four levels of applied fertilizer, two of which formed part of the factorial experiment, nil (NIL), every fourth year (P4YN4Y), every second year (P2YN2Y), and annually (P1YN1Y). There were a total of 13 annual fertilizer applications (P1YN1Y). Fertilizers used were superphosphate, ammonium sulfate, or mixtures of the two, resulting in large quantities of S and Ca also being applied (Table 1). Fertilizers were broadcast by hand.

Sampling and Analysis
Foliar samples were collected before fertilizer treatments at Ages 10 (just before the sixth annual fertilization), 12, 14, and 20 yr (3 yr after the final fertilizer treatment). Fully expanded first-year leaves were sampled and analyzed. Three selected trees per plot were sampled by climbing and sampling, or using a shotgun to collect twigs. Leaves from the three trees were stripped from each branch and combined, on the basis of equal mass, for each plot. Samples were prepared and analyzed as described by Neilsen et al. (1992). Drying was performed at 70°C before the sample was ground in a Wiley mill before analysis.

The impact of fertilization on forest soils was considered by examining differences in soils between unfertilized and fertilized plots at Age 20 yr. Pits were dug to a depth of 1.0 m, in the center of each NIL and P1YN1Y plot, between tree rows. Within these pits soil horizons were described and sampled for analysis. Physical and chemical parameters for each horizon were measured and analyzed. Additionally, soils on all plots were sampled by soil auger to a depth of 50 cm, in 10-cm increments. Each 10-cm increment sample was bulked from each of four auger holes per plot. Soils for mineral N extraction were maintained moist and sieved to <2 mm for chemical analysis. Remaining soils were air dried and sieved to <2 mm for chemical analysis as described by Ringrose and Neilsen (2005). Bulk density for soils was calculated from intact cores sampled from soil pits, in 10-cm increments, to a depth of 50 cm.

Forest floor organic matter was collected in autumn using a 25 by 20 cm frame. Samples were separated into two horizons, the undecomposed samples were O1 horizon and decomposed samples were the O2 horizon (McDonald et al., 1990). Only the O2 horizon was analyzed. Chemical analyses of samples were performed as described by Ringrose and Neilsen (2005).

Data Analysis
Analysis of variance and least significant difference tests were used to test the significance of treatment and soil profile depths on nutrient content, while group regression analysis was used to evaluate growth response (Genstat 5 Committee, 1988). Significance is reported at the p < 0.05 level.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Growth and Health of Plantations
There was a significant response to applied N, at the rate of 700 kg N ha^–1, but no response to applied P, at the rate of 322 kg P ha^–1, during the experimental period and no interaction between N and P (Fig. 1) .

View larger version (14K): [in this window] [in a new window]   Fig. 1. Growth of E. regnans fertilized with factorial combinations of N and P, applied two yearly following initial application at Age 6 yr. Arrows indicate four yearly applications. Bars indicate least significant difference between treatments (LSD).

View larger version (16K): [in this window] [in a new window]   Fig. 2. Growth of E. regnans unfertilized or fertilized with N plus P, annually, two yearly or four yearly, following initial application at Age 6 yr. Arrows indicate four yearly applications. Bars indicate least significant difference between treatments (LSD).

Foliar N and P concentrations varied among treatments and sampling times. In general, foliar N concentrations ranged from 1.09 to 1.40% between treatments, though this was not significant (Table 2). Despite higher foliar P content in P2YN2Y, (0.16% P at Ages 14 and 20 yr) this treatment did not produce more growth than N2Y (foliar P content of 0.10%). This higher P content resulted in a significantly higher N/P ratio for N2Y, varying over the four sampling periods from 16.1 to 18.6, compared with N/P ratios of 7.3 to 12.3 for P2YN2Y. Neither foliar Ca nor foliar S concentrations reflected differences in quantities of these nutrients applied in various treatments. Foliar Ca concentrations were high, ranging from 0.5 to 1.0%, while S concentrations were in the range considered adequate, falling between 0.11 to 0.14%.

Fertilizer treatments significantly reduced pH by up to 0.7 of a unit in the top 0- to 50-cm soil depth, and by 0.6 of a unit in the O2 horizon (Table 5). Higher rates of N plus P fertilizer (P2YN2Y and P1YN1Y) resulted in significantly lower soil pH. Treatments P2Y and N2Y also caused significant drops, which were of the same order as that resulting from P2YN2Y. In the O2 horizon, significant declines in pH occurred only in P1YN1Y. At the highest rate, annual fertilization resulted in an overall pH reduction from 4.6 to 3.9. The greatest reduction, of 0.9 units, was in the surface 10 cm of soil.

Exchangeable Mg was also significantly reduced in the soil profile to a depth of 50 cm in N2Y and in the surface 10 cm for P1YN1Y (Table 5). Total Mg was not significantly affected by either N or P fertilization (Table 4). Total Ca in the soil, to the depth of 50 cm, was significantly reduced by N2Y, to 50% of that in NIL. Exchangeable Ca was lower when N was applied alone compared with P applied alone or in combination with N. Base saturation was also substantially reduced by fertilization, by about 50 to 60% throughout the profile. There was no significant effect of N or P fertilization on exchangeable K concentrations.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Growth Responses
Eucalypt plantation growth is frequently limited by N availability (Cromer et al., 1975; Schönau and Herbert, 1989). Responses of eucalypt plantations to later age N and P additions have been variable and site specific (Cromer et al., 1981; Weston et al., 1991). In this study, growth response indicated that the site was limited by N availability, but not P availability. This was in agreement with the soil nutrient concentrations, where P (perchloric acid digest) was in moderate supply (100–250 µg g^–1) while N content was low (<3000 µg g^–1) (Grant et al., 1995). Despite the moderate soil P concentrations, foliar P contents, from Age 10 to 20 yr, were low and some response may have been expected. However, the absolute requirements of eucalypts for P were generally less than for pines (Baker and Attiwill, 1985). Ward et al. (1985) also found height growth response only to N and P in combination, a positive interaction, but no response to P applied alone.

In a P. radiata plantation, periodic applications of N (100 kg N ha^–1) through 15 yr, resulted in improved growth increases depending on the amount of N applied (Ringrose and Neilsen, 2005). Fertilizer response efficiency was higher with applications every second or fourth year than with annual application. In the present study, Eucalyptus regnans growth at the highest rate of fertilization was more than double that of the unfertilized treatment.

We observed no correlation of growth response and foliar N content. This is in agreement with the findings of Judd et al. (1996), but contrary to those of Ballard (1978). The foliar N and P contents were similar to those measured in native forest stands in Tasmania (Neilsen and Palzer, 1977; Adams and Attiwill, 1988), but the foliar N contents of around 1.2 to 1.3% were slightly lower than those measured in E. regnans in New Zealand (Frederick et al., 1985). Accumulation of P, applied as fertilizer, in the E. regnans foliage further suggested that P was not a limiting factor. When N was applied, but not P, growth was as good as when both N and P were applied. This was despite low foliar P levels of 0.07 to 0.08% and an N/P ratio of 17, compared with foliar P levels of 0.16% and an N/P ratio of eight after P fertilization. This suggests that the requirements for P in E. regnans may be lower than indicated in other eucalypt species (Dell et al., 2002).

Changes in Nutrient Distribution within Soil and O2 Horizons
In this study, at the highest rate of fertilization, N, P, S, and Ca all accumulated within the O2 horizon. The O2 horizon of the most heavily fertilized treatment had over seven times the N content of unfertilized plot, equivalent to about 60% of the N applied. However, the soil to a depth of 50 cm contained less N in the fertilized treatment. In a review of 19 studies across the United States and Europe, Fenn et al. (1998) also noted the importance of surface horizons retaining N, with the majority of labeled N applied in studies being retained in the forest floor and mineral soil. In contrast, in a warm temperate climate in New Zealand high rates of forest floor breakdown in E. regnans resulted in low amounts of accumulation of 4.7 to 11.0 Mg ha^–1 (Frederick et al., 1985), compared with the 102 Mg ha^–1 in the annual fertilization treatment in this study.

Soil Acidification
Reductions in soil pH were associated with higher rates of single superphosphate and ammonium sulfate fertilizers and with the two combined. In our research, the pH decline was greatest in the surface 10 cm with acidification decreasing down the soil profile. Theoretical pH changes have been estimated within agricultural surface soils (0–15 cm). Within an acid sandy loam, application of 45 kg N ha^–1 as ammonium sulfate would lower the pH by about 0.1 pH units. In contrast, a three-fold application would be needed to produce the same effect in a more highly buffered acid clay loam (McGarity and Storrier, 1986). However, at the high rates of fertilizer used in this study, the acidification at the E. regnans site was as great as that reported in a Typic Haplohumult soil under P. radiata (Ringrose and Neilsen, 2005), despite higher clay content in this soil. In this study, pH generally declined with increasing rates of fertilization. This is in agreement with a study of soil solution pH changes under eucalypt plantations in Tasmania by Smethurst et al. (2001), which noted that the relationship between rate of N application and pH decline was predominantly linear or log-linear, and was affected by the rate rather than the timing of fertilization.

In another study in northern Tasmania, application of triple superphosphate at the rate of 70 kg P ha^–1 or annual applications of urea for 3 yr at the rate of 100 kg N ha^–1 yr^–1, to a Eucalyptus nitens plantation, on a Haplohumult soil, had no significant effect on pH. However, the application of the N and P fertilizers combined significantly reduced pH by 0.2 of a unit to a depth of 50 cm. Doubling the amount of urea fertilizer, to 200 kg N ha^–1 yr^–1, for a 3-yr period significantly reduced pH by 0.3 units (Paul Adams, Forestry Tasmania, personal communication, 2003). The application of urea has been shown not to affect the pH of agricultural soils as strongly as ammonium sulfate and ammonium nitrate (Porter et al., 1995). In a similar fertilization experiment to this study, in an Eucalyptus globulus plantation, on Hapludult soil in northern Tasmania, at the highest rate of fertilization soil pH to a depth of 50 cm had reduced by 1.0 pH unit.

In the current study, decreases in soil pH also occurred due to superphosphate additions. However, there was no cumulative effect of N and P fertilizer in combination, with N alone having as great an effect as N and P combined. In a previous study, addition of higher rates of P with N, to P. radiata, resulted in a significantly lower pH (Ringrose and Neilsen, 2005). In both the current study and that under P. radiata large amounts of S were applied, which would have contributed to acidification in the soils. Acidification has been reported for many agricultural soils in Australia from the use of nitrogenous fertilizers (Porter et al., 1995), but contrary to our findings, research in agricultural soils has generally shown no pH decline associated with application of superphosphate (McGarity and Storrier, 1986). In an agricultural soil (Aeric Fragiaqualf), application of superphosphate at similar rates to this study (45–60 kg ha^–1 yr^–1 during 7 yr) in general had no effect on pH in the top 7.5 cm (Manoharan et al., 1995). Reductions in exchangeable Mg in the surface soil were associated with pH changes following annual fertilizer application (Ringrose and Neilsen, 2005).

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Substantial growth responses were measured from periodic applications of N and N plus P fertilizer, but responses of P applied alone did not differ significantly from the NIL treatment. These growth responses indicated that the site was limited by N availability but not P availability. Applications every second year had improved fertilizer use efficiency compared with yearly applications. At the highest rate of fertilization, the O2 horizon contained over seven times the N content of the NIL treatment, equivalent to about 60% of the N applied. Phosphorus, S, and Ca also accumulated within the O2 horizon, showing the importance of this layer as a nutrient reserve.

This study indicates that the productivity of eucalypt plantations on nutrient-poor soils can be increased significantly through periodic fertilization. However, despite the soils being deep and well structured, considerable reductions in pH result from heavy rates of fertilization. In contrast to agricultural soils, application of P as single superphosphate alone or in combination with nitrogenous fertilizers reduce soil pH in these forest soils. From this and other research, pH changes have been seen to vary with quantity and type of fertilizer applied. Monitoring soil parameters should be a part of the development of any long-term, high rate fertilizer regime for forest soils.

	ACKNOWLEDGMENTS

 
The establishment, measurement and analysis of the research experiment was funded by Forestry Tasmania. Wally Pataczek managed the research for many years with assistance from a number of field and research staff. The final analyses were supported by the Cooperative Research Centre for Sustainable Production Forestry CRCSPF and Rayonier Tasmania.

Received for publication July 11, 2004.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 

• Adams, M.A., and P.M. Attiwill. 1988. Nutrient cycling in forest of N.E Tasmania. Research Report 1. Tasmanian Forests Research Council Inc., Hobart, Australia.
• Attiwill, P.M., and G.W. Leeper. 1987. Forest soils and nutrient cycles. Melbourne University Press, Melbourne.
• Baker, T.G., and P.M. Attiwill. 1985. Above-ground nutrient distribution and cycling in Pinus radiata D. Don and Eucalyptus obliua L'Herit. Forests in Southeastern Australia. For. Ecol. Manage. 13:41–52.
• Ballard, R. 1978. Effect of first rotation phosphorus applications on fertilizer requirements of second rotation radiata pine. N.Z. J. For. Sci. 8:135–145.
• Ballard, R., and G.M. Will. 1978. Past and projected use of fertilizers in New Zealand forests. N.Z. J. For. Sci. 8:15–26.
• Cromer, R.N., D.M. Cameron, J.N. Cameron, D.W. Flinn, W.A. Neilsen, M. Raupach, P. Snowdon, and H.D. Waring. 1981. Response of eucalypt species to fertiliser applied soon after planting at several sites. Aust. For. 44:3–13.
• Cromer, R.N., M. Raupach, A.R.P. Clark, and J.N. Cameron. 1975. Eucalypt plantations in Australia—The potential for intensive production and utilization. Appita 29:165–172.
• Dell, B., N. Malajczuk, D. Xu, and T.S. Grove. 2002. Nutrient disorders in plantation eucalypts. 2nd ed. Australian Centre for International Agricultural Research (ACIAR), Canberra.
• Fenn, M.E., M.A. Poth, J.D. Aber, J.S. Baron, B.T. Bormann, D.W. Johnson, A.D. Lemly, S.G. McNulty, D.F. Ryan, and R. Stottlemeyer. 1998. Nitrogen excess in North America ecosystems: Predisposing factors, ecosystem responses, and management strategies. Ecol. Appl. 8:706–733.
• Frederick, D.J., H.A.I. Madgwick, M.F. Jurgensen, and G.R. Oliver. 1985. Dry matter content and nutrient distribution in an age series of Eucalyptus regnans plantations in New Zealand. N.Z. J. For. Sci. 15:158–179.
• Genstat 5 Committee. 1988. Reference manual. Oxford Science Publication, Oxford.
• Gentle, S.W., F.R. Humphreys, and M.J. Lambert. 1965. An examination of a Pinus radiata phosphate fertilizer trial fifteen years after treatment. For. Sci. 11:315–324.
• Grant, J.C., M.D. Laffan, R.B. Hill, and W.A. Neilsen. 1995. Forest Soils of Tasmania. A handbook for identification and management. Sprinta Print Pty Ltd, Launceston.
• IUCN. 1992. Protected areas of the world: A review of national systems. Volume 1. Indomalaya, Oceania, Australia and Antarctic. IUCN, Gland, Switzerland and Cambridge, UK.
• Judd, T.S., L.T. Bennett, C.J. Weston, P.M. Attiwill, and P.H. Whiteman. 1996. The response of growth and foliar nutrients to fertilizers in young Eucalyptus globulus (Labill.) plantations in Gippsland, southeastern Australia. For. Ecol. Manage. 82:87–101.
• Manoharan, V., P. Loganathan, and R.W. Tillman. 1995. Effects of long-term application of phosphate fertilisers on soil acidity under pasture in New Zealand. p. 85–91. In R.A. Date et al (ed.) Third International Symposium on Plant–Soil Interactions at Low pH. Kluwer Academic Publisher, Brisbane.
• McDonald, R.C., R.F. Isbell, J.G. Speight, J. Walker, and M.S. Hopkins. 1990. Australian soil and land survey field handbook. 2nd ed. Inkata Press, Melbourne.
• McGarity, J.W., and R.R. Storrier. 1986. Fertilizers. p. 305–333. In J.S. Russell and R.F. Isbell (ed.) Australian soils: The Human Impact. University of Queensland Press, St Lucia.
• Neilsen, W.A. (ed.) 1990. Plantations handbook. Forestry Commission, Tasmania.
• Neilsen, W.A. 1996. Response of Eucalyptus nitens and Eucalyptus regnans seedlings to application of various fertilizers at planting and soon after. N.Z. J. For. Sci. 26:355–369.
• Neilsen, W.A., G.R. Davis, J.G. McDavitt, and W. Pataczek. 1984. Growth and nutrient uptake of Pinus radiata seedlings over the first 3 years following treatment with nitrogen and phosphorus fertilizers. Aust. For. Res. 14:1–10.
• Neilsen, W.A., and C. Palzer. 1977. Analysis of foliar samples of healthy and dieback Eucalyptus obliqua. Aust. For. 40:219–222.
• Neilsen, W.A., W. Pataczek, T. Lynch, and R. Pyke. 1992. Growth response of Pinus radiata to multiple applications of nitrogen fertilizer and evaluation of the quality of added nitrogen remaining in the forest system. Plant Soil 144:207–217.[CrossRef]
• Porter, W.M., C.D.A. McLay, and P.J. Dolling. 1995. Rates and sources of acidification in agricultural systems of southern Australia, p. 75–83. In R.A. Date et al (ed.) Third International Symposium on Plant-Soil Interactions at Low pH. Kluwer Academic Publishers, Brisbane.
• Ringrose, C., and W.A. Neilsen. 2005. Growth response of Pinus radiata and soil changes following periodic fertilization. Soil Sci. Soc. Am. J. 69:(this issue).
• Schönau, A.P.G., and M.A. Herbert. 1989. Fertilizing eucalypts at plantation establishment. For. Ecol. Manage. 29:221–244.
• Smethurst, P.J., A.M. Herbert, and L.M. Ballard. 2001. Fertilization effects on soil chemistry in three eucalypt plantations. Soil Sci. Soc. Am. J. 65:795–804.[Abstract/Free Full Text]
• Tamm, C.O., and B. Popovic. 1995. Long-term field experiments simulating increased decomposition of sulfur and nitrogen to forest plots. Ecol. Bull. 44:301–321.
• Ward, S.C., G.E. Pickersgill, D.V. Mitchaelsen, and D.T. Bell. 1985. Responses to factorial combinations of nitrogen, phosphorous and potassium fertilizers by saplings of Eucalyptus saligna Sm., and the prediction of the responses by DRIS Indices. Aust. For. Res. 15:27–32.
• Weston, C.J. 2001. An overview of recent nutrition research for the rapidly expanding Eucalyptus plantation industry in Australia. Gottsein Foundation Report. University of Melbourne, School of Forestry, Creswick.
• Weston, C.J., P.M. Attiwill, and J.N. Cameron. 1991. Growth and nutrition of eucalypt plantations in relation to soil type and former land use in Gippsland, Victoria. p. 480–491. In A.P.G. Schönau (ed.) IUFRO Symposium on intensive forestry: The role of Eucalypts. Vol. 1. Southern African Institute of Forestry, Durban, South Africa.

This article has been cited by other articles:

				C. Perdomo, J. Duran, and P. Llovet Soil and Plant Indices for Predicting Eucalypt Response to Nitrogen in Uruguay Soil Sci. Soc. Am. J., September 28, 2007; 71(6): 1708 - 1718. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ringrose, C. Articles by Neilsen, W. A. Search for Related Content PubMed Articles by Ringrose, C. Articles by Neilsen, W. A. Agricola Articles by Ringrose, C. Articles by Neilsen, W. A. Related Collections Soil Fertility and Productivity Frozen Soils Nitrogen