2 Standards and Regulations of Sludge Applications in Malaysia, the USA, and Europe

228



Ab. Aziz bin Abd. Latiff et al.



Table 7.11

European community limit (after CEC 1986) a (26)

Pollutant



Concentration in

soil (mg/kg)



Concentration in dry

sewage sludge (mg/kg)



Annual application rate

(kg/ha/year)b



Cadmium

Copper

Nickel

Lead

Zinc

Mercury



1–3

50–140

30–75

50–300

150–300

1–1.5



20–40

1,000–1,750

300–400

750–1,200

2,500–4,000

16–25



0.15

12

3

15

30

0.1



a Assume soil pH range of 6–7.

b Based on average 10 years.



4. CASE STUDIES AND RESEARCH FINDINGS

Researches showed that majority of crops were able to adsorb almost heavy metals and

concentrated in the tissues with or without effect to the crop’s yield depending on the types and

concentration of heavy metals applied. One of the factors that influences an uptake of heavy

metal by the crops is soil pH. Normally, maximum yield of crops are achieved in the soil pH

range of 5.5–6.5 and decrease below or above the range. Based on the study, the soil pH falls

slightly below this range (pH = 5.2). However, there are exceptions in the case of lupines and

treacle performing well in more acidic soils, whereas medics such as Lucerne prefer alkaline

soils. The problem of low soil pH occurs in regions of excess rainfall of 500 mm per annum

and irrigated areas. The problems of high pH are common in lower rainfall environments

with calcareous sands and cracking clays as well as with many nonsaline sodic soils. Soil

composition varies widely, and it reflects the nature of the parent material. The principle

factors determining these variations are the selective incorporation of particular elements in

specific minerals during igneous rock crystallization, the relative rates of weathering, and the

modes of formation of sedimentary rocks.

Studied showed that most of pH values of all treatment ponds was in the normal range

(pH ≈ 7.0), while COD, TS, and TVS parameters vary from each other. Domestic sludge

sample from Community septic tank treatment plant was the highest concentration to COD,

TS, and TVS, which were 79,900, 16.0, and 12.54 mg/L, respectively, while Activated sludge

was the lowest concentration to TS and TVS, which were 1.34 and 0.28 mg/L as shown in the

Table 7.12.

Studies on heavy metals content in the domestic sludge showed that cadmium range from

0.001–0.100 mg/kg (dry weight), chromium from 0.091–0.285 mg/kg (dry weight), copper

from 0.131–0.569 mg/kg (dry weight), lead from 0.212–0.555 mg/kg (dry weight), nickel

from 0.300–2.324 mg/kg (dry weight), and zinc from 0.180–3.129 mg/kg (dry weight). The

concentration of those heavy metals after application to soil was 1.1211, 54.450, 57.113,

397.62, 844.42, and 183.38 mg/kg (dry weight) for cadmium, chromium, copper, lead, nickel,

and zinc as shown in Table 7.13. Metal concentrations of sludge are presented in Table 7.14.

Based on the U.S. Environmental Protection Agency (22) Part 503 and European Community



Heavy Metal Removal by Crops from Land Application of Sludge



229



Table 7.12

Characterization of domestic sludge in Malaysia

Parameter



Community septic Activated sludge Oxidation pond Aerated lagoon

tank (CST)

(AcS)

(OP)

(AL)



pH

COD, mg/L

Total solids, mg/L

Total volatile solids, mg/L



7.22

79,900

16

12.54



7.16

29,600

1.34

0.28



6.92

31,500

3.99

1.25



7.03

26,400

13.61

10.05



Table 7.13

Heavy metals content in the domestic sludge sample

Subject

Cadmium

Heavy metal in studied

domestic sludge (range)

Heavy metal in soil after

applied sludge



Concentration of elements, mg/kg (dry wt.)

Chromium

Copper

Lead

Nickel



0.001–

0.100

1.1211



0.091–

0.285

54.450



0.131–

0.569

57.113



0.212–

0.555

397.62



Zinc



0.300–

2.324

844.42



0.180–

3.129

183.38



Table 7.14

Comparison of heavy metals content to USEPA and European community limit

Element



Concentration of elements, mg/kg (dry wt.)

Cu

Pb

Ni



Cd

This study (average)

USEPA, Part 503

European

Community Limit



Cr



0.003

85

20–40



0.203

3,000

N.S



1.202

4,300

1,000–1,750



0.37

840

750–1,200



1.077

420

300–400



Zn

1.46

7,500

2,500–4,000



Limit, the content of heavy metals substance in domestic sludge studies remains well below

the limit values.

The heavy metal concentration range was different in the plants after being applied by

domestic sludge as shown in the Table 7.15. Three types of plants were chosen to be studied

of heavy metal uptake by crops; Ipomoea aquatica, Spinacea oleracea and Brassica juncea.

Spinacea oleracea has shown a good uptake of metal cadmium and zinc, while ipomoea

aquatica and Brassica juncea have shown a good uptake of metal chromium, copper, lead,

and nickel. It also showed a good sign of heavy metal mobility in plant–soil system.

Table 7.16 shows a distribution of heavy metals content in plants cross-section (%). The

distribution of heavy metal in different parts of the crops is variable depending on the type

of heavy metal. Most metals are more concentrated in root tissues of plants than in stem and

leaves tissues, especially for lead, nickel, and copper.



230



Ab. Aziz bin Abd. Latiff et al.



Table 7.15

Heavy metals content in the plants sample

Type of plants



Average concentration of heavy metals content, mg/kg (dry wt.)

Cadmium

Chromium

Copper

Lead

Nickel

Zinc



Ipomoea aquatica

Spinacea oleracea

Brassica juncea



0.251

1.26

0.15



10.83

8.4

9.27



37.68

17.45

22.42



32.96

23.05

26.25



213.2

24.06

32.24



63.47

118.25

88.83



Table 7.16

Distribution of heavy metals content in plants cross-section (%)

Cross-section

Leaves



Stems



Roots



Type of plant

Ipomoea aquatica

Spinacia oleracea

Brassica juncea

Ipomoea aquatica

Spinacia oleracea

Brassica juncea

Ipomoea aquatica

Spinacia oleracea

Brassica juncea



Cd



Cr



Cu



Pb



Ni



29.055

26.928

39.092

40.685

13.459

22.504

30.818

59.652

38.403



38.085

12.545

16.15

23.363

32.173

29.608

38.573

55.275

54.242



27.644

24.563

13.315

21.527

18.76

44.155

50.959

56.706

42.53



12.862

12.508

12.803

13.342

9.1241

23.595

73.666

78.378

63.602



31.646

11.681

19.367

26.806

15.702

30.74

41.562

72.625

49.893



Zn

30.586

18.908

26.075

36.411

28.595

35.008

32.927

52.531

38.917



Table 7.17

Design example for sample from Indah Water Konsortium (IWK), Malaysia

Heavy metal



Cadmium, Cd

Chromium, Cr

Copper, Cu

Lead, Pb

Nickel, Ni



Biosolids

concentrations

(mg/kg)



APLR

(kg/ha/year)



2.0

14.4

147.1

33.0

15.6



1.9

150

75

15

21



AWSAR =



APLR

(tons/ha)

(0.001) Conc. In biosolids



1.9/(0.001 × 2.0) = 950.0

150/(0.001 × 14.4) = 10,416.7

75/(0.001 × 147.1) = 509.9

15/(0.001 × 33.0) = 454.5

21/(0.001 × 15.6) = 1,346.2



5. DESIGN EXAMPLE

By using data from Indah Water Konsortium (IWK), Malaysia for Kluang location as shown

in Table 7.6, the determination of the annual whole sludge application rate could be calculated

as shown in Table 7.17.



6. FUTURE DIRECTION RESEARCH

Studies show that landfarming method is capable of reducing the concentration of heavy

metals in the samples. From the result of this study, landfarming technique is suitably applied

to the palm oil farm because the concentration of heavy metals could be reached into an eatable



Heavy Metal Removal by Crops from Land Application of Sludge



231



tissue lesser. Anyway, further study should be done to make sure the concentration of heavy

metals in an eatable tissue. For future research, the determination of heavy metals uptake rate

for several of plants could be done. Further study would be able to gain the range of heavy

metal constant uptake rate by the crops (27, 28).



REFERENCES

1. Abdul Kadir Mohd Din, Mohamed Haniffa Abd. Hamid (1998) The management of municipal

wastewater sludge in Malaysia. Paper work for IEM Talk on sewage sludge management issues.

Petaling Jaya, Kuala Lumpur, Malaysia

2. Lu Q, He ZLL, Graetz DA, Stoffella PJ, Yang XE (2010) Phytoremediation to remove nutrients

and improve eutrophic stormwaters using water lettuce (Pistia stratiotes L.). Environ Sci Pollut

Res. 17:84–96

3. Aswathanarayana U (1995) Geoenvironment: an introduction. AA Balkema, Rotterdam,

pp 107–203

4. Bingham FT (1979) Bioavailability of Cd to food crops in relation to heavy metal content of

sludge-amended soil. Environ Health Perspect 28:39–43

5. Aziz MA, Koe LCC (1990) Potential utilizing of sewage sludge. In: Meeroff DE, Bloestcher F

(eds) (1999) Sludge management, processing, treatment and disposal. Fla Water Resour J Nov

1999:23–25

6. Salt D et al (1995) Phytorextraction: a novel strategy for the removal of toxic metals from the

environment using plants. Biotechnology 13:468–474

7. Chaney RL, Malik M, Li YM, Brown SL, Angle JS, Baker AJM (1997) Phytoremediation of soil

metal. Curr Opin Biotechnol 8:279–284

8. Raskin I, Ensley BD (2000) Phytoremediation of toxic metal: using plants to clean up the environment. Willey, New York

9. Shen ZG et al (1997) Uptake and transport of zinc in the hyperaccumulator Thlaspi caerulescens

and the non-hyperaccumulator Thlaspi ochroleucum. Plant Cell Environ 20:898–906

10. Mc Grath SP (1995) Chromium and nickel. In: Alloway BJ (ed) Heavy metals in soils. Blackie

Academic & Professional, UK, pp 156–162

11. Brooks RR (ed) (1998) Plants that hyperaccumulate heavy metals. CAB International, Wallingford,

p 379

12. Baker AJM et al (1991) In situ decontamination of heavy metal polluted soils using crops of

metal-accumulating plants – A feasibility study. In: Hinchee RF, Olfenbuttel RF (eds). In situ

bioreclamination. Butterworth-Heinemann, Stoneham, MA, pp 539–544

13. Brown SL, Cheney RL, Angle JS, Baker AJM (1994). Zinc and cadmium uptake by Thlaspi

caerulescens and Silene vulgaris in relation to soil pH. J Environ Qual 23:1151–1157

14. Brooks RR et al Hyper accumulation of Nickel by Alyssum Linnaeus (Cruciferae). Proc R Soc

Lond B203:387–403

15. Ebbs SB, Kochian LU (1997) Toxicity of zinc and copper to Brassica species: implications for

phytoremediation. J Environ Qual 26:776–781

16. Banuelos GS, Terry N (2000) Phytoremediation of contaminated soil and water. Lewis Publisher,

Boca Racon.

17. Alloway BJ (1995) Heavy metals in soil, 2nd edn. Blackie Academic & Professional, New York

18. APHA, AWWA & WEF(1992) Standard methods for the examination of water and wastewater,

18th edn. American Public Health Association, Washington



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19. Dhanagunan G, Narendran M (2001) Sewage sludge as an alternative for soil nourishment in

Malaysia. dlm. National conference on contaminated land. Petaling Jaya Hilton, Petaling Jaya,

Selangor

20. Priestly AJ (1995) Modern techniques in water and wastewater treatment. CSIRO Publisher, East

Melbourne

21. Anderson TA, Watson BT (1992) Comparative plant uptake and microbial degradation of

trichloroethylene in the Rhizosphere of five contaminated surface soils. ORNL/ITM-12017, Oak

Ridge, TN, 186 pp

22. U.S. EPA 1994. Land application of sewage sludge: a guide for land appliers on the requirements of

the federal standards for the use or disposal of sewage sludge, 40 CFR Part 503. EPA 831/B/9/002b.

U.S. Environmental Protection Agency, Washington, DC

23. Alloway BJ, Jackson AP (1991) The behavior of heavy metals in sewage sludge-amended soils.

Sci Total Environ 100 Spec No:151–176

24. U.S. EPA (1994) A plain English guide to the EPA part 503 biosolids rule. EPA 832/R/93/003.

U.S. Environmental Protection Agency, Washington, DC

25. Mengel K, Kirkby EA (2001) Principles of plant nutrition, 5th edn. Kluwer Academic Publishers.

(Springer-Verlag, New York, NY) 849 pp

26. Huang PM, Iskandar IK (1999) Soils and ground water pollution and remediation. Lewis Publisher,

London. 386 pp

27. Wang LK, Shammas NK, Evanylo G (2008) Engineering and management of agricultural and

application. In: Biosolids Engineering and Management. Wang LK, Shammas NK, Hung YT (eds).

Humana Press, Totowa, NJ, pp 343–417

28. Wang LK, Ivanov V, Tay JH, Hung YT (eds) (2010) Environmental Biotechnology. Humana Press,

Totowa, NJ, 975 pp



8

Phytoremediation of Heavy Metal Contaminated Soils

and Water Using Vetiver Grass

Paul N. V. Truong, Yin Kwan Foong, Michael Guthrie,

and Yung-Tse Hung

CONTENTS

G LOBAL S OIL C ONTAMINATION

R EMEDIATION T ECHNIQUES

V ETIVER G RASS AS AN I DEAL PLANT FOR P HYTOREMEDIATION

P HYTOREMEDIATION U SING V ETIVER

C ASE STUDIES

R ECENT R ESEARCH IN H EAVY M ETAL PHYTOREMEDIATION U SING

V ETIVER

F UTURE L ARGE S CALE A PPLICATIONS

B ENEFITS OF P HYTOREMEDIATION WITH V ETIVER G RASS

C ONCLUSION

R EFERENCES

Abstract Phytoremediation includes utilization of plants to remediate polluted soils. In this

chapter, application of Vetiver grass in phytoremediation of heavy metal contaminated soils

is discussed. Case studies in Australia, China, and South Africa are presented. The future

application may be in the areas of mine site stabilization, landfill rehabilitation, leachate

treatment, wastewater treatment, and other land rehabilitation. It is a low-cost remediation

method.



1. GLOBAL SOIL CONTAMINATION

Due to ever increasing industrial, agricultural, and mining activities worldwide, heavy

metal pollution of land and water is becoming a globally important environmental, health,

economic, and planning issue. There is an increase in world population, and unpleasant

disposal of industrial effluents, especially in the developing countries, causing soil pollution.

Utilization of these lands for agricultural purposes and urban developments requires a safe

From: Handbook of Environmental Engineering, Volume 11: Environmental Bioengineering

Edited by: L. K. Wang et al., DOI: 10.1007/978-1-60327-031-1_8 c Springer Science + Business Media, LLC 2010



233



234



P. N. V. Truong et al.



and efficient decontamination process. With the increasing use of agrochemicals to maintain

and improve soil fertility, unwanted elements such as cadmium into soils due to contaminated

sources of fertilizers, especially in developing countries, are being introduced into agricultural

soils, which poses a potential threat to the food chain (1, 2). Mining and industrial operations

also lead to significant challenges for the management of the natural environments during

and after these activities.The increased public awareness of the environmental impact of such

activities demands an interdisciplinary, inter-organizational, and international effort (3). Soil

and water contaminated with heavy metals pose a major environmental and human health

problem that needs an effective and affordable technological solution (4).



2. REMEDIATION TECHNIQUES

2.1. Physical and Chemical Techniques

Various physical and chemical techniques to decontaminated soils have been undertaken

during the last 25 years (5–8) and millions of dollars being spent by governments all over

the world on preventive measures. However, all of them are labour intensive and costly, and

cannot be applied to thousands of hectares of land contaminated with inorganic heavy metals

(8, 9). These technologies results in rendering the soil biologically dead and useless for plant

growth as they remove all flora, fauna, and microbes including useful nitrogen fixing bacteria

and P-enhancing mycorrhizal fungi (10).

Many sites around the world remain contaminated with no remediation in sight simply

because it is too expensive to clean them up with the available technologies (11). If these

wastes cannot be economically treated or removed, steps must be taken to prevent offsite contamination of the food chain processes through wind and water erosion, leachate

generation (9).



2.2. Bioremediation Techniques

Microbial bioremediation technology, well known for decontamination of organics (12),

is not available for large-scale biodegradation of inorganic heavy metals. The health hazards

caused by the accumulation of toxic metals in the environment together with the high cost of

removal and replacement of metal-polluted soil have prompted efforts to develop alternative

and cheaper techniques to recover the degraded land (10).



2.3. Phytoremediation

The restoration of derelict land by establishing a plant cover is important before it poses

serious health hazard by transferring the trace metals into the surroundings. Current research

in this area includes utilization of plants to remediate polluted soils and to facilitate improvement of soils structure in cases of severe erosion, the innovative technique being known as

phytoremediation (1, 8, 10, 13).

Phytoremediation is widely considered to be not only an innovative but also an economical

and environmentally compatible solution to many engineering and environmental issues

across the world. Although essentially simple, this new technology branches further and

into a variety of different fields and techniques. A review of tropical hyperaccumulator of



Phytoremediation of Heavy Metal Contaminated Soils and Water Using Vetiver Grass 235

heavy metal plants and concluded that there is a lack of investigation for the occurrence of

hyperaccumulator plant species. No botanical or biogeochemical exploration of trace metal

tolerant and/or accumulating plant species has yet taken place in many parts of the world.

Many plant species, which can accumulate high concentrations of trace elements, have been

known for over a century (17). Renewed interest in the role of these hyper-accumulating

plants in phytoremediation has stimulated research in this area (8, 17). Several plant species or

ecotypes, associated with heavy metal enriched soils, accumulate metals in the shoots. These

plants can be used to clean up heavy metal contaminated sites by extracting metals from soils

and accumulating them in aboveground biomass (10, 13, 14).

2.3.1. Phytoextraction



This is a technique that utilizes plants known as heavy metal hyper accumulators and metal

accumulating plants with large biomass to extract heavy metals such as Pb, Zn, Cu, and Cd.

The plants are then harvested to allow the removal of contaminants from site (15).

2.3.2. Phytofiltration



This technique uses plant roots, grown in aerated water to concentrate and precipitate

heavy metals from polluted effluents. Plants that can adapt to wetland conditions are the most

suitable (15).

2.3.3. Phytostabilization



This technique relies on plants to stabilize contaminants in soils, rendering them harmless.

Plants with low metal accumulating properties but that are tolerable to high heavy metal

concentrations are most suited to this technique (15).

2.3.4. Phytovolatilization



This technique is useful for the removal of volatile metals such as Hg and Se. Plants extract

these metals and volatilize them from the foliage.

2.3.5. Phytomining



There are several plant species or ecotypes, associated with heavy metal enriched soils,

accumulate metals in the shoots. These plants can be used to clean up heavy metal contaminated sites by extracting metals from soils and accumulating them in aboveground biomass

(13, 14). The metal enriched biomass can be harvested and smelted to recover the metal.

2.3.6. Limitations of Phytoremediation



Although phytoremediation is the least destructive method among the different types of

remediation because it utilizes natural organisms and the natural state of the environment can

be preserved, it has its limitations like all other biological methods: it has not yet been found

to remove or reduce contaminants completely (16). Furthermore, any vegetative method of

remediation may be more suited to a long-term application due to the time it takes for the

plants to grow.

The use of a vegetative and effective erosion and sediment management program has proven

to be viable. Vegetative methods are the most practical and economical; however, revegetation



236



P. N. V. Truong et al.



of these sites is often difficult and slow due to the hostile growing conditions present, which

include toxic levels of heavy metals (9).

2.3.7. Plants for Phytoremediation



Plants that are used to extract heavy metals from contaminated soils have to be the most

suitable for the purpose, i.e. tolerant to specific heavy metal, adapted to soil and climate, capable of high uptake of heavy metal(s), etc. Plants either take up one or two specific metals in

high concentrations into their tissues (hyperaccumulator) with low biomass (1), or extract low

to average heavy metal (not metal specific) concentrations in their shoots with high biomass.

Low biomass hyperaccumulators, generally, have a restricted root system (17). In contrast,

nonaccumulators, high biomass producing and tolerant plants have physiological adaptation

mechanisms, which allow them to grow in contaminated soils better than others (18). The

tolerance and specific behaviour at the root level must be taken into consideration while

selecting plants for phytoremediation (19). Root system morphology allows some plants to

be more efficient than others in nutrient uptake in infertile soil or stressed soil conditions (20).

Phytoremediation is considered an innovative, economical, and environmentally compatible solution for remediating some heavy metal contaminated sites (4) among others. The next

step is to find suitable species of vegetation with the ability to develop this technology on a

large scale. This chapter deals with some experiments conducted in Australia using Vetiver.



3. VETIVER GRASS AS AN IDEAL PLANT FOR PHYTOREMEDIATION

The success of phytoremedial efforts is dependent largely upon the choice of plant species.

Among the plants involved in phytoremedial measures, Vetiver grass (Chrysopogon zizanioides L (Roberty), formerly Vetiveria zizanioides L. (Nash)), should receive special attention

(Fig. 8.1).



Fig. 8.1. Vetiver – Shoot and Root. Left Vetiver grass has stiff and erect stems with sterile flower heads,

reaching 3 m high under good growing conditions. Right Deep, extensive and penetrating root system,

capable of extending to 3.3 m in the first year of growth, and to 4.5 m in 3 years.



Phytoremediation of Heavy Metal Contaminated Soils and Water Using Vetiver Grass 237

Vetiver is one of those few plants which possess both economical and ecological capabilities, i.e. essential oil distilled from its roots in over 70 countries (21) and its conservation

properties, such as up to 2 m high plant with a strong dense and mainly vertical root system

often measuring more than 3 m, useful in soil erosion control (15, 22–25). It is propagated

vegetatively and is noninvasive (26). It is extremely resistant to insect pests and diseases (27)

and is widely used worldwide for soil and moisture conservation and soil restoration. It is

immune to flooding, grazing, fires, and other hazards (28). Vetiver grass is regarded as a

tool for environmental engineering (32) and as one of the most versatile crops of the third

millennium (33).



3.1. Unique Morphology and Physiology

Vetiver is a fast growing, perennial grass native to the South and South-East Asian regions.

It will grow to approximately 1–2 m in height and has long been used in Asia for slope stabilization in agricultural lands because of a deep (up to 3 m), strong root system. Traditionally,

these roots were woven into mats, fans, and fragrant screens (34).

Vetiver is used throughout the world in various cultivars; however, it has been shown that

although Vetiver does adapt to its environment over time, most nonfertile genotypes such as

Monto, Sunshine, Vallonia, and Guiyang are genetically identical (35). It can then be said that

most application with specific results obtained by research can be applied with confidence

throughout the rest of the world.

Vetiver grass is both a xerophyte and a hydrophyte and, once established, is not affected by

droughts or floods (17)

The unique characteristics of Vetiver can be summarized as follows:

•

•

•

•

•

•

•



Adaptability to a wide range of soil and climatic conditions

Can be established in sodic, acidic, alkaline, and saline soils

Tolerant to drought due to deep and extensive root system

Mature plants are tolerant to extreme heat (50◦ C) and frost (−10◦ C)

Vetiver can withstand burning, slashing, and moderate tractor traffic

Resistant to infestations from most pests, diseases, and nematodes

Absence runners or rhizomes, and only spreads by tillering



3.2. Tolerance to Adverse Soil Conditions

Extensive researches over a decade by the senior author has uncovered the ability of Vetiver

grass to grow on both acidic and alkaline soils and tolerate a wide range of heavy metals

at various concentrations. It has been demonstrated that Vetiver has a very high tolerance

to heavy metals such as Arsenic, Cadmium, Copper, Chromium, Lead, Mercury, Nickel,

Selenium, and Zinc when compared to most other plants



3.3. Tolerance to High Acidity and Manganese Toxicity

Experimental results from glasshouse studies show that when adequately supplied with

nitrogen and phosphorus fertilizers, Vetiver can grow in soils with extremely high acidity and

manganese. Vetiver growth was not affected, and no obvious symptoms were observed when

the extractable manganese in the soil reached 578 mg/kg, soil pH was as low as 3.3, and plant



238



P. N. V. Truong et al.



manganese was as high as 890 mg/kg. Bermuda grass (Cynodon dactylon) which has been

recommended as a suitable species for acid mine rehabilitation, has 314 mg/kg of manganese

in plant tops when growing in mine spoils containing 106 mg/kg of manganese (36). Therefore, Vetiver, which tolerates much higher manganese concentrations both in the soil and in

the plant, can be used for the rehabilitation of lands highly contaminated with manganese.



3.4. Tolerance to High Acidity and Aluminum Toxicity

Results of experiments where high soil acidity was induced by sulfuric acid show that

when adequately supplied with nitrogen and phosphorus fertilizers, Vetiver produced excellent

growth even under extremely acidic conditions (pH = 3.8) and at a very high level of soil

aluminum saturation percentage (68%). Vetiver did not survive an aluminum saturation level

of 90% with soil pH = 2.0; although a critical level of aluminum could not be established

in this trial, observation during the trial indicated that the toxic level for Vetiver would be

between 68 and 90% (37, 38). This level was later confirmed by field observation, where

Vetiver survived on a sandy soil with an aluminum saturation level of 86% (Fig. 8.2)



3.5. Tolerance to High Soil Salinity

Results of saline threshold trials showed that soil salinity levels higher than ECse = 8 dS/m

would adversely affect Vetiver growth, while soil ECse values of 10 and 20 dS/m would reduce

yield by 10 and 50%, respectively (Fig. 8.3).

These results indicate that Vetiver grass compares favourably with some of the most salt

tolerant crop and pasture species grown in Australia (Table 8.1) (Fig. 8.3).

In an attempt to revegetate a highly saline area (caused by shallow saline groundwater),

a number of salt tolerant grasses, Vetiver, Rhodes (Chloris guyana), and saltwater couch

(Paspalum vaginatum) were planted. Negligible rain fell after planting. So plant establishment



Fig. 8.2. Vetiver growth on aluminum saturated soil. When adequately supplied with N and P fertilizers, Vetiver growth was not affected when soil aluminum saturation extract (ASE) reached 68%, and

soil pH at 3.8. ASE higher than 45% is highly toxic to both crop and pasture plants. Field sampling

indicated that Vetiver grew on site with ASE at 86%.