Resin & Wax Holdings Ltd

Address: PO Box 5228, Auckland, New Zealand P 6493772002 F 6493695800

SYNOPSIS

Successful restoration of the peat harvest area for agricultural or other use, following extraction of the resin and wax from the peat by solvent and return back to the area from where it was harvested assumes that the extraction process does not adversely affect the peat as a medium for plant or natural vegetation growth. The peat deposit at Kaimaumau has an average depth of 2.7 metres, a maximum depth of 5.8 metres and thins out on the edges and in the vicinity of sand ridges that intersect the area. The peat is generally black in colour, well-decomposed and contains considerable amounts of woody material with relatively few recognisable plant remains. It is known that kauri forest (Agathis australis) has occupied the area on at least three separate occasions; the oldest kauri stumps have been carbon-dated at 41,000 to 38,000 years B.P. The area has been subjected to gum digging over a long period and the surface is heavily pockmarked with water-filled holes from this activity. The soils of the peat lands have been mapped by NZ Soil Bureau as Ruakaka peaty sandy loam and loamy peat, are poorly drained and are of low natural fertility. Study has been conducted in both laboratory and glasshouse by the Soil Bureau of DSIR referenced below to assess the effects of solvent extraction on Ruakaka loamy peat as a medium for plant growth. The study concluded that

1. Extraction of Ruakaka loamy peat with hot solvent does not impair its water-holding properties providing the moisture content of the peat prior to extraction is not reduced to low levels.

2. Isopropanol extraction does not have any significant detrimental effect on the nutrient status of the peat

3. The plant growth in the treated peat was comparable to that in un-extracted peat. 4. Ruakaka peat is strongly acid, very nitrogen deficient, but contains reasonable levels

of calcium, magnesium, phosphorus and sulphur. The peat sample was prepared using Kaimaumau peat. The extracted peat sample was prepared by extracting peat with Isopropanol as the extracting solvent. RWHL plan to use n-butyl acetate as the extracting medium. Both IPA and n-BuAc are suitable solvents both biodegradable and similar chemical characteristics. Ruakaka loamy peat is a basin peat formed from rushes and ferns under a high water table where anaerobic conditions have led to the accumulation of organic matter. Because of their proximity to coastal dune sands they have accumulated considerable amounts of windblown sand. The bulk sample studied contained more than 50% fine sand (0.1 _.. 02 mm material) which gives the peat its loamy characteristics. The peat also contains

Resin & Wax Holdings Ltd

Address: PO Box 5228, Auckland, New Zealand P 6493772002 F 6493695800

considerable amounts of woody material derived from the former kauri forests that colonised then area. Physical measurements on the peat carried out at a bulk density of 0.6 g cm 3 indicate high water holding capacities (42% by volume) and medium to high values for plant 'available' water (20% by volume). Isopropanol extraction had a small but insignificant effect on moisture retention. However, when the peat was oven-dried moisture holding capacity decreased and available water dropped to 11% by volume. Since the peat is to be dried down to a figure of 33% moisture (dry weight basis), no losses of moisture holding capacity will occur. Chemical studies showed that the peat is strongly acid, has a high capacity to retain nutrients and contains adequate amounts of calcium, magnesium, phosphorus and sulphur, for plant growth. Because of a high C/N ratio, it is very deficient in nitrogen and the available potassium content is low. Isopropanol extraction brought about small decreases in the total carbon, nitrogen, phosphorus and adsorbed sulphur contents, and an apparent increase in available calcium and magnesium. These changes are of no great significance, but these chemical properties should be monitored when extraction is done on a commercial scale. The glasshouse experiments show that nitrogen deficiency 1S the most important factor limiting ryegrass growth on the peat. To a lesser extent potassium, magnesium and phosphorus were limiting to growth, although the response to phosphorus and magnesium did not occur in the extracted peat, possibly because of a release of these nutrients' during the drying of the peat. No trace element deficiencies were evident and foliar analysis confirmed that the supply of copper, manganese, iron and zinc was adequate for good growth. Liming experiments indicated that lime was not necessary for ryegrass, but for white clover liming to pH 5.5 plus inoculation of clover seed with rhizobium bacteria was necessary for good growth. Results from the glasshouse and laboratory experiments cannot be extrapolated directly to the field and field experiments will be needed. However, the laboratory and glasshouse studies will provide sound basis for the planning of meaningful field trials.

Reference

Widdowson J.P. and Watts H.M., “Laboratory and Glasshouse Studies of Ruakaka Loamy

Peat” Soil Bureau, Department of Scientific and Industrial Research (DSIR) NZ 1980

LABORATORY AND GLASSHOUSE STUDIES,

ON RUAKAKA LOAMY PEAT

by

J.P. Widdowson and H.M. Watts

Soil Bureau, Department of Scientific and Industrial ResearchLower Hutt, New Zealand

-~~ •••_.... ~~~ ~. .~ -" - ~ "" t......~-~....

INTRODUCTION

Kauri Deposit Surveys Ltd has applied for a'mining licence in order to

drain and systematically mine some 2,200 hectares of peat at Kaimaumau,

Northland, extract the natural resins and subsequently return the extracted

peat to the land to allow reclamation of the area for agricultural use.

Details of the project concept and environmental assessment are given

by Cuttriss, McKenzie and Martin (1979) and information on the extraction of

resins and other products from the Kaimaumau peat deposits is given by

Spencer, Thomas and Associates (1979).

The licence area is situated about 27 k north of Kaitaia with the

northern and eastern part of the area bounded by sandhills and the shoreline

at Rangaunu Bay. The southern and western portion is generally bounded by

farmland, some of which has been reclaimed from the peat swamp. The peat

has an average depth of 2.7 metres, a maximum depth of 5.8 metres and thins

out on the edges and in the vicinity of sand ridges that intersect the

area.

The peat is generally black in colour, well-decomposed and contains

considerable amounts of woody material with relatively few recognisable plant

remains. It is known that kauri forest (Agathis australis) has occupied

the area on at least three separate occasions; the oldest kauri stumps

have been carbon-dated at 41,000 to 38,000 years B.P. The area has been

subjected to gum digging over a long period and the surface is heavily pock­

marked with water-filled holes from this activity.

The soils of the peatlands have been mapped (N.Z. ·Soil Bureau, 1954)

as Ruakaka peaty sandy loam and loamy peat, are poorly drained and are of

low natural fertility.

2

Successful restoration of the mined area for agricultural use,

following extraction of the peat with isopropanol assumes that the extraction

process does not adversely affect the peat as a medium for plant growth.

Studies were therefore undertaken in both laboratory and glasshouse at

Soil Bureau, Lower Hutt, to assess the effects of solvent extraction on

Ruakaka loamy peat as a medium for plant growth. This paper reports the

effects of isopropanol on some physical and chemical properties of the peat

and on the growth and nutrient uptake of ryegrass and white clover grO\VTI

on the peat.

SAMPLE PREPARATION

Two bulk samples of peat were obtained from the Industrial Processing

Division, D.S.I.R. in December 1979. The samples were part of as-tonne

consignment of peat from Area 4 at Kaimaumau, Northland, which had been dried

and sieved at Paraparaumu Airport. One of the samples had been extracted

with isopropanol in the pilot plant of Industrial Processing Division.

Prior to carrying out glasshouse experiments and physical and chemical

analysis, the bulk samples were sieved « 6 mm) and moistened to near field

capacity (~ 70% w/w) and stored In polythene sacks. Samples for chemical

analysis were air-dried and passed through a 2 mm sieve.

WATER HOLDING PROPERTIES

Methods

Sieved samples of Ruakaka loamy peat were packed into brass rlngs

(68.6 cm 3 volume, approx. 5.4 cm diameter x 3 cm long) to an equivalent

dry bulk density of about 0.6 g cm- 3• Moisture release characteristics

were determined using the pressure plate apparatus (hanging water column

and air pressure) for matric potentials do\\~ to -1 bar and a pressure membrane

system was used at -IS bars according to the methods described by Gradwell (1971:

All measurements were

3

Saturated hydraulic conductivities were measured on cores packed as

above using the fixed head method of Klute (1965).

replicated at least three times.

Results

The peat material has high water-holding capacities with 'plant-

available water' contents (water held between -0.2 bars and -15 bars) being

about 34% by weight or 20% by volume (many soils are in the range of 10-20%

by volume). Alcohol extraction has not significantly changed the water

retention characteristics although there is a slight loss of water-holding

ability at, and just drier than, saturation (see Fig. 1). In contrast,

oven-drying the peat has significantly reduced the moisture retention, the

plant available water being approximately 17% by weight or 11% by volume.

This probably results from induced hydrophobic or water repellency conditions

which are commonly observed in dried peat. Some practical ,consequences

of this phenomenon in the field would be slower water infiltration rates

and, therefore, increased surface runoff of rain Kater and poorer water

storage within the peat could result in drought stress for pasture or crops.

Saturated hydraulic conductivities were slow at 1.8 mm hr- 1 for both

the alcohol-extracted and non-extracted peat (dried peat was not tested).

However, this value probably represents the worst possible practical situation

since it was measured using sieved peat \vith all of the coarse, woody material

removed and the compaction to 0.6 g cm- 3 dry bulk density would be a maximum

in the field situation. Tests are underway to examine more realistic values

(i.e., entire samples with lower compaction rates).

CHEMICAL PROPERTIES

Chemical analyses were carried out according to the methods of Blakemore

et al. (1972) on extracted and non-extracted peat samples in order to:

1. Assess the chemical properties of Ruakaka loamy peat.

140

130

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30

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~ Extracted, non-dried peat

~ Extracted, oven-dried peat

a--------__4r---- -=-_._-......,~

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Fi g. 1.

Matric potential (bars)

Moisture retention by Ruakaka loamy peat, as affected by alcohol-extraction and drying.

5

"

2. Assess the plant nutrient status of the peat.

3. Assess the effect of isopropanol extraction at 70°C on chemical

properties and nutrient status.

The analyses (Table 1) show that the peat is strongly acid (pH 4.1) and

contains about 46% (w/w) organic matter. pH vaiues made on air-dried

samples are normally 0.5 pH units lower than values obtained on field moist

samples. The peat has a high CIN ratio - a characteristic which reflects

a high proportion of plant residues, particularly woody and fibrous material.

Peats and organic soils with C/N ratios of 30 or more will immobilise

mineral nitrogen causing the soil medium to be nitrogen deficient.

The peat has a high cation exchange capacity which is a measure of the

ability of the peat to retain the nutrients calcium, magnesium, potassium

and sodium against leaching. As a medium for plant growth, the peat is

strongly acid but contains adequate amounts of calcium, magnesium, phosphorus

and sulphur. Nitrogen is likely to be very deficient and potassium is

likely to be limiting especially under intensive cropping.

Extraction of the peat with isopropanol has affected some of the

chemical properties of the peat. There has been a decrease in organic

carbon, nitrogen, total phosphorus and adsorbed sUlphur contents. On the

other hand, there has been an increase in total exchangeable cations viz.

calcium and magneslum. An explanation for the increase in exchangeable

calcium and magnesium is that isopropanol, being non-ionic, is unable to

desorb any exchangeable calcium and magnesium. But because the isopropanol

is removing resins and waxes from the peat which are essentially inert with

respect to the cations calcium and magnesium, there is a relative increase

in concentration. The small decreases in available phosphorus (Truog P),

exchangeable potassium and sodium are of little significance.

Isopropanol therefore in removing resins, waxes and other extractables

does remove some carbon, nitrogen, phosphorus and SUlphur from the peat,

but has little effect on the exchangeable cations; in fact it appears

to give a relative increase in calcium and magnesium. Water-soluble

Table 1.

6

Chemical properties of Ruakaka loamy peat.

Property Non-extracted IsopropanolExtracted

pH 4.1 4.4

Carbon % 27.1 21. 8

Nitrogen % 0.30 0.26

C/N 90 84

Total phosphorus (mg %) 41 33

Truog phosphorus (mg %) 10 9

Adsorbed sulphur (ppm) 138 129

Cation exchange capacity (me %) 73.4 74.0

Exchangeable calcium (me %) 14.6 20.2

Exchangeable magnesiwn (me %) 1. 20 1. 35

Exchangeable potassiwn (me %) 0.25 0.24

Exchangeable sodium (me %) 0.43 0.39

Total cations 2: (me %) 16.5 22.2

Base saturation (%) 22 30 .

7

Table 2. Ratings for chemical pl"opcrties

The following ratings for chemical properties are usedby Soil Bureau for New Zealand soils:

Phosphorus p Adsorbedretention' S04

Rating Truog 0.51'.1 H2 SO4 (%) (ppm 5)

(mg %) (mg %)

Very high > 5 > 40 90-100 > 150. ,

High 3-5 20-40 60-90 50-150

Medium 2-3 10-20 30-60 15-50

Low 1-2 5-10 10-30 5-15

Very low < -1 < 5 0-10 < 5

Rating Organic C Total N C/N pH (1:2.5 soil:water)(%) (%)

Very high > 20 >1.0 > 24 ) > 9.0 (extremely alkaline)) 8.4-9.0 (strongly " )) 7.6-8.3 (moderately " )

High 10-20 0.6-1.0 16-24 ) 7.1-7.5 (slightly· II )) 6.6-7.0 (near neutral)

Medium 4-10 0.3-0.6 12-16 ) 6.0-6.5 (slightly acid)) 5.3-5.9 (moderately II )

LO\'1 2-4 0.1-0.3 10-12 4.5-5.2 (strongly " )Very 10\'/ 2 < 0.1 <10 < 4.5 (extremely " )

Cation-Exchange Properties

Rating CEC L Cat BS Ca Mg K Na(me.%) (me.%) (%) (me.%) (me.%) (me.%) (me.%)

Very high > 40 > 25 80-100 > 20 > 6 > 1.2 > 2

High 25-40 15-25 60-80 10-20 3·:6 0.8-1.2 0.7-2

Medium 12-25 7-15 40-60 5-10 1-3 0.5-0.8 0.3-0.7

Low 6-12 3-7 20-40 2-5 0.3-1 0.3-0.5 0.1-0.3

Very low < 6 < 3 <: 20 < 2 < 0.3 <: 0.3· <: 0.1

8

nutrients, such as nitrate nitrogen, would be ~xtracted by isopropanol,

but the amounts present in an acid peat would be negligible.

GLASSHOUSE EXPERIMENTS- ,

Pot experiments under glasshouse conditions were carried out to assess

the nutrient status of Ruakaka peat both before and after extraction with

isopropanol using perennial ryegrass as the test plant. Since both

experiments showed yield depressions when the peats were limed to pH 5.5,

further experiments with both perennial ryegrass and white clover were

carried out to assess the yield response to lime over a range of pH values.

Finally, the effects of liming, inoculation with rhizobium bacteria and

nitrogen on white clover growth \"ere examined in a factorial pot trial.

EXPERIMENT I. Nutrient status of peat before and after extraction with

isopropanol.

Methods

Ryegrass Lolium perenne was grown in 15 cm plastic pots containing the

moist equivalent of 660 g of oven-dry sieved « 6 mrn) peat for three months

under glasshouse conditions. In this experiment the response of ryegrass

to lime and the nutrients nitrogen, phosphorus, potassium, sulphur,

magnesium, iron, copper, zinc, manganese, and boron was examined using a

llsubtractive ll technique (Andrews and Fergus, 1964). In the "subtractive"

technique treatments were applied by supplying all nutrients needed for

plant growth except one and a complete nutrient treatment in which all

nutrients are added to the soil. In a subtractive treatment ryegrass is

dependent on the peat for its supply of that nutrient that has been omitted

and the extent to which growth is 1imi ted provides a mea-sure of the

adequacy or deficiency of that particular nutrient.

9

Lime (at 8.0 g CaC0 3 per pot) and phosphorus (0.25 g Ca(HZ

P04)z per

pot) were mixed into the peat prior to potting, whereas all other nutrients

were applied in sOlution after emergence of ryegrass and again after each

harvest. The total quantities of nutrients (mg) applied to each pot,

during the experiment were: N, 404; P, 66.2; K, 376; S, 104; Mg, 76;

Ca,3588; Fe,10.6; Cu,12.8; Zn,11.2; Mo,2.0; Mn, 36.8 and B, 7.2.

The experiment was run in two parts. The unextracted peat experiment

ran from 22 February to 15 May and the extracted peat experiment ran from

8 July to 8 October 1980, in a glasshouse maintained between 18 and 26°C.

Distilled water was added regularly to adjust soil moisture content to field

capacity. Three harvests were made at 3-4 weekly intervals and the

harvested material was dried at lODC and weighed. Dried material from

the third harvest was ground in a Tema mill, pressed into discs and

analysed for both major and minor nutrients by X-ray fluorescence spectro-

graphy.

Results

Unextracted peat

Dry matter yields over three harvests, given in Fig. 2, showed that on

unextracted peat nitrogen, phosphorus and magnesium were limiting for the

growth of ryegrass. A severe nitrogen deficiency is clearly the most

important factor limiting growth, a result which was predicted from the

high C/N ratio of this peat. lfuile phosphorus is shown to be limiting

for optimum growth, the presence of high values of Truog P in the peat,

together with a phosphorus concentration of 0.30% (Table 3) in ryegrass

leaves at the third harvest, indicates that phosphorus is not markedly

deficient. It would appear that under glasshouse conditions which were

favourable for good growth of ryegrass, the rate of phosphorus supply to

plant roots was below optimum.

The response to added magnes1urn 1S considered to be due to the

correction of an imbalance between exchangeable calcium and magnesium

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40

20

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* Denotes significantdifference (at 5% level)from 'c' treatment.

o

c -N -p -K -S -Mg -Fe -Cu -TE -L o

Fi g. 2.

Subtrac,tive treatments

Dry matter yields from unextracted peat (expressed as percentage of'complete' treatment).

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tes significanterence (at 5% level)

'c' treatment.

......

c -N -p -K -S -Mg -Fe -Cu -TE -L O+L o

Fi g. 3.

Subtractive treatments

Dry matter yields from extracted peat (expressed as percentage of'complete' treatment).

Table 3. Element content of ryegrass from unextracted peat at harvest 3.

Sample % ppmCa K Cl S P Si Al ~1g Na Mn Fe Cu Zn

C 1. 01 4.12 0.88 0.42 0.29* 0.28 0.01 0.28 0.13 273 93 9 66

-p 1. 17 3.96 0.78 0.41 0.30* 0.44 0.01 0.28 0.15 305 145 10 68

-K 1. 08 0.56* 0.74 0.38 0.33 0.38 0.02 0.40 2.59 294 137 10 74

-S 1.16 3.88 1.12 0.42 0.30* 0.36 0.21 0.30 0.15 313 118 10 72

-Mg 1. 04 3.66 0.70 0.40 0.34 0.35 0.007 0.23 0.37 285 107 10 76

-Fe 1. 04 3.94 0.80 0.42 0.31 0.31 0.01 0.30 0.10 305 101 10 75

-Cu 0.98 3.94 0.79 0.42 0.31 0.32 0.01 0.26 0.11 294 101 6 65

-TE 0.96 3.71 0.74 0.43 0.26-k 0.21 0.01 0.30 0.19 128 109 8 41

-L 0.78 3.86 0.87 0.41 0.35 0.24 0.01 0.26 0.14 303 116 10 82

Critical0.2 1.7 0.2 0.24 0.30 0.13 0.05 20 40 4 10Level - -

* Deficient

.......N

Table 4. Element content of ryegrass from extracted peat at harvest 3.

Sample% ppm

Ca K C1 S P Si Al Mg Na Mn Fe Cu Zn

C 0.79 3.32 0.75 0.64 0.41 0.18 0.003 0.33 0.35 248 76 7 60

-p 0.77 3.36 0.93 0.57 0.31 0.20 0.005 0.33 0.39 243 83 7 84

-K 0.74 0.49* 1.08 0.57 0.54 0.24 <0. 003 0.37 2.44 269 76 8 67

-S 0.86 3.41 2.36 0.38 0.42 0.20 <0. 003 0.33 0.39 233 80 8 58

-~1g 0.77 3.36 0.67 0.65 0.37 0.18 <0.003 0.28 0.55 222 74 8 61

-Fe 0.79 3.44 0.70 0.62 0.43 0.20 <0.003 0.35 0.35 262 76 7 57

-Cu 0.78 3.41 0.69 0.65 0.42 0.19 <0.003 0.31 0.33 250 79 7 59

-TE 0.79 3.37 0.42 0.69 0.41 0.18 <0.003 0.33 0.41 188 72 7 56

-L 0.72 3.43 0.94 0.72 0.39 0.19 <0.003 0.35 0.38 223 78 8 51

Critical 0.2 1.7 0.2 0.24 0.30 0.13 0.05 20 40 4 10level - -

* Deficient

Vl

14

that would be aggravated by liming with pure calcium carbonate. Ryegrass

yields were greater in the absence of lime than where it had been added.

Although the peat is acid it does contain adequate amounts of calcium

for good growth and it is likely that soluble aluminium, which usually

restricts growth in acid mineral soils with pH values less than 5.0, is

not a problem in these peats. The depression to liming was therefore

considered to be due to a reduction in the availability of trace elements.

However, trace element contents of ryegrass leaves from the third harvest

(Table 3) shows that levels of manganese, iron, copper and zinc ln the

presence of added lime are adequate for plant growth.

The significant depression in yield due to the addition of the trace

elements zinc, boron and manganese has been shown to be due to an excess

amount of boron added to the peat. Ryegrass receiving boron treatment

showed a browning of the tips of older leaves and excess concentrations

of boron \.,Jere found in the leaves.

Extracted peat

Dry matter yields over three harvests, given in Fig. 3, showed that on

the extracted peat a severe deficiency of nitrogen, and a slight deficiency

of potassium were limiting ryegrass growth. Compared with the unextracted

peat, no deficiency of phosphorus or magnesium were observed. Because it

was shoh~ in the discussion on the chemical properties of peat before and

after extraction that isopropanol had little effect on the nutrient status

of the peat, the differences in ryegrass growth were unexpected. Two

factors may have affected the results obtained. The experiment on the

extracted peat was carried out at a different time of the year when initial

growth rates of ryegrass were slower due to shorter day-length. Under

these conditions of slower growth, the demand for both phosphorus and magnesium

by the ryegrass would be l~ss and hence no depression in growth was obtained

in the minus phosphorus and magnesium treatments. The other factor which

may have contributed was that prior to the experiment the extracted peat

]S

was oven-dried to remove residues of isopropanol that were present 1n the

sample obtained from the extraction plant. The effect of oven-drying has

probably resulted in some mineralisation of organic matter which has

increased the availability of phosphorus and magnesium in the growing medium.

No depression was obtained to the addition of trace elements as a

result of reducing the amount of boron added to one quarter of that added

to the unextracted peat. Nor was there any depression in ryegrass yield

from the addition of lime. Because of the inconsistencies in the response

to lime added to peat, further work was undertaken.

The element content of ryegrass leaves from the third harvest (Table 4)

indicates adequate levels of both major and trace elements.

EXPERIMENT 2. Responses to ryegrass and white clover to liming on

Ruakaka loamy peat.

Methods

Pot trials were carried out to assess the optimum pH for ryegrass

and white clover growth on unextracted Ruakaka loamy peat in the absence

and presence of added trace elements.

1. Ryegrass

Prior to potting up, lime was added at the rate of 0, 2.68, 5.35, 8.03

and 13.38 g A.R. CaC03

to the moist equivalent of 670 g oven-dry sieved

« 6 mm) unextracted peat and allowed to equilibrate for 14 days.

After 14 days the pH values on the liming treatments were 4.81, 5.27,

5.69, 6.02 and 6.39. Prior to planting, Ca(H2P0

4)2 at the rate of

100 ppm P was mixed throughout all soils. Ryegrass was sown into

15 cm plastic pots and after emergence the trace element treatments

were factorially applied to the pots along with a nutrient solution

which supplied N, K, S, Ca and Hg. Trace element treatments and

basal major nutrients were applied again prior to the first harvest of

ryegrass and again after the first and second harvests. The total

quantities of nutrients (mg) supplied were identical to those used in

16

the subtractive experiments with boron reduced to 1.40 mg per

pot. There were three replications and the layout was a randomised

complete block.

The experiment ran from 4 August to 26 November 1980 in a glasshouse

maintained at 18°-26°C and soil moisture was adjusted regularly to

field capacity with distilled water: The ryegrass was harvested three

2.

times at 3-4 weekly intervals and the harvested material was dried at

70 0 e and weighed.

White clover

In this experiment, identical rates of lime and trace elements were used

as in the ryegrass liming experiment. White clover was sown into IS em

plastic pots containing the moist equivalent of 640 g oven-dry sieved

« 6 rnrn) unextracted peat that had received lime and phosphate prior

to potting. Fourteen days after sowing the clover seedlings were

inoculated with a suspension of rhizobium bacteria. Two \I'eeks later

the trace element treatment was applied factorially together with

nutrient solution which supplied K, S, Ca and Mg tQ all pots. Trace

element treatments and basal major nutrients were applied again prior to

first harvest and again after first and second harvests. Apart from

nitrogen, which was omitted from the white clover experiment, the total

amounts of nutrients applied were identical to those used in the

subtractive experiments. There were three replicates arranged in

randomisedcomplete blocks. The experiment ran from 16 September 1980

to 13 January 1981 and was maintained under the same conditions as the

ryegrass experiment.

Results

1. Ryegrass

Dry matter yields for the three harvests are sho\~~ in Fig. 4. Over the

whole experiment ryegrass yields decreased significantly with liming

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.; '. 1.~ ':.~". "", ...

:~.:\ ~~:

'"., ..•: :;', ,.;

5.7

pH

r---

~.<\I"\.:",

'!'f\,,":(,~ I .

~~<:~'\:\,

\", ,

~:~~<'1>'",,I,. ,\'~.' ~; ,. ~ ,,\.. :.""':, '0".' .\~"'rl,~ "

" J\· .I\~.1_ •,,'.'';. t'·... ' ~,,\. ~

\',.:..,

:<'~~.~ ,.,",.. '~ ~. I

• • h~ ': ;

\' ~ ;:.,.,\

, ',",\1 1 \'

:.'t·.,: .'

~.}.1 ~\"

6.0

r-

~~:t ,......., 'I

1"".

.~.::/}.. ,:, ~ '.:;:, ..

. 'I"

\, 'M.~.""

.'~ ': ::l't l,'

:'1'~ J,\".··.·:.(.l''.:.1

'~'.II,':~~:;

:/.:~.'. ' ..\: ...I"::,:"', ','

/ '..I' • .,

'1".-',

;(>:'~~';~'~ ..', ..~ .. ' ~

6.4

c=J No trace elements

l):f~l Trace elements added

I LSD (5%)

-..J

Fi g. 4. Responses of perennial ryegrass to liming.

Table 5. Element content of ryegrass as affected by trace elements,and 1iming.

pH Trace % ppmelements P K Mg Ca Mn Fe Cu Zn

4.8 TO 0.46 4.72 0.25 0.84 111 86 8 35

T10.44 4.84 0.26 0.81 189 88 12 58

5.3 TO 0.42 4.90 0.25 0.77 107 92 8 44

Tl

0.43 4.81 0.26 0.83 176 88 11 53

5.7 TO 0.40 4.80 0.23 0.83 100 92 8 46

Tl0.43 4.84 0.23 0.83 165 88 11 54

6.0 TO 0.38 4.72 0.24 0.84 77 91 8 47

Tl

0.39 4.79 0.23 0.82 147 90 11 SO

6.4 TO 0.33 4.63 0.22 0.89 51 95 8 48

Tl0.31 4.57 0.24 0.93 96 97 10 45

Critical level 0.30 1.7 0.13 0.20 20 40 4 10

00

19

and with addition of trace elements. Total yields at S.7 and 6.0

were significantly less than those at pH 4.8 and 5.3; likewise, yields

at pH 6.4 were significantly lower than those at pH 6.0.

A depression to liming is normally associated with reduced plant

availability of trace elements at higher pH'levels. However, those

element levels shown for the first harvest material (Table 5) indicate

satisfactory element contents over all pH values and only phosphorus

and manganese are sho\m to decrease with increasing pH.

The decrease in ryegrass yield with addition of trace elements

cannot be explained from the element contents shown in Table 5. The

content of manganese, copper and zinc were increased by the addition

of trace elements but In no instance are these levels excessive for

ryegrass growth. It is possible, however, that boron uptake (results

not available) may have been excessive in the trace element treatments.

From this experiment we may conclude that neither liming nor

trace element addition is beneficial for ryegrass growth on this peat.

2. h~ite clover

Dry matter yields for the three harvests are sho~~ in Fig. 5. Over

the whole experiment clover yields increased significantly with liming,

with near maximum yields being obtained at pH 5.7. Trace element

addition appears to increase clover yields at pH 4.8 and 5.3, but

these differences were not significant. Pale leaf colours in clovers

at pH 4.8 and 5.3 during the establishment phase suggested that

inoculation may not have been fully effective. The interaction of

liming, inoculation and added nitrogen was therefore investigated

in a later trial.

From this experiment we can conclude that liming to near pH 5.7

will produce optimum yields of white clover.

c=J No trace elements

9-

8 -

7 -

~

-IJ0 6-0.,"-0'

'0 5 -.--iQ)

'"><~ 4 -Q)-IJ-IJnjE

>< 3-~Cl

2-

1-

1-,-,~,

'If"1, .'1~ , ..'< ,j

r-1X~.,;\", '}'/1/1,,:, I, I,'" .. ;.,.';\"\':.\'

" 1:,\'. ~':7::\:," J I

. I;....:I' ,~.'\~.

'. '" I

"';'.'l.: .'I~:":.\ ..":'J. ,'t

:~:;.~~~:~. ';',; '.: ~il" :(

... ~ "......."" ... :{''":

4.8

r-;""":",'-

~;.\~~ ,I;"

~:,,~

.' " '-:,.\1.,

,...--.

',r:'~.,.' t''0','','.. ::\','I: ~(~

~ I 'I'"

" 0".. ,,~ .'~ ..", ,\', ,

I ~ ',.1.~ ...... ,¥

',J.;",".\,':'. ,'.• 10"

.:': .',',,'

.' , '" ~ i

:~\:.:, ;',, I~, ~',':,,!",\0-''';

5.3

":,",'\" ~. ,:I";: .,~,~ .

.~:.,~:-

', ..'" ..

::'f'::::~'~1',,'

.~. ,. ". ......... /.'

~·S·::·Ill' '~':.. t"~~~>t

:'., :,',

5.7

pH

t-"'-

~': . \ ..~, (:.

::'::~,:•~ j' ~,:

~ \~'\'','. t\, I::.~.:- .. ",

\ \,:,:;<:'~1.

"1" ..:(1'.. : .'..t.· ,,'1:\•.:

~:'~:''::;:::.':',::;"', .•,J

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

r~:). \,,\,

,.1,\".. ' ,'. ~,\;:

";';':".' ~ ,:,.'{,;;."l.'..',

~j\:,/0,'

''.,\.,"', ol..

1"\,.\',J. I.

\ :'" ~

6.0

,t:~~~.l L~

.:,:~ ;,,~,:.....~. .', ....: s;.. .

<":'\!~':,".' !...~, ,, .\.,\'.1 )" .'t.~;''';\~. \';,:

.-,' \

>~~:)"~Vj'·I!',·

'1""""" I\' ;,,.'•• 1 ' •) .... i:

;I~\~.~,",',:'", ......~~ ',\:::~:~,

'.~:)~:.,1~..;..,'

::},~," ...

<:;';,j:'~': ::•• ' I,~

6.4

ill! Trace. "It

ILSD

elements added

(5%)

1'0o

Fi g. 5. Responses of white clover to liming.

EXPERIMENT 3.

21

Response to lime, inoculation and nitrogen In white

clover.

Acid Ruakaka loamy peat, with a high C/N ratio is an inhospitable

medium for clover growth. In general, clovers germinating in such soils

will not survive for long unless infected and coionised by root nodule

bacteria (rhizobia). The rhizobia penetrate the roots of young clover

seedlings and stimulate the host plants to form nodules. In these nodules

colonies of bacteria provide clovers with nitrogenous compounds, synthesised

from free nitrogen present in the soil atmosphere.

l\~ite clover normally responds to liming of acid peats because of the

sensitivity of the rhizobia to acid soil conditions. Because white clover

in the previous liming experiment appeared to establish slowly in the unlimed

treatment (pH 4.8) further work was carried out to examine the effects of

inoculation and liming of white clover in the presence and absence of

added nitrogen.

Methods

The three factors examined were:

1. Lime: 0 and 7.93 g CaC03/pot to give pH values of 4.8 and 6.0.

2. Inoculation: No inoculation and inoculation with a suspension of

Rhizobium trifolii obtained from a commercial culture

"Nitrogerm".

3. Nitrogen a and 100 ppm nitrogen as NaNO applied In solution to3

seedlings 8 days after emergence.

The experiment was a 2 x 2 x 2 factorial with two replications in a

completely random layout. Lime was mixed throughout the soils 14 days before

sowing and a basal application of Ca(H PO) at 100 ppm P was mixed into the2 4 2

peat prior to potting.

lfuite clover was sown into 15 cm plastic pots containing the moist

equivalent of 640 g of oven-dry peat. The inoculum was applied to the seed

at sowing. Nitrogen was applied in solution 8 days after seedling emergence

8

22

~\" ,.",'• c.". I'

,,:0.' .pH 4.8

6-

+l00.."'-0">

4'-'drlQJ

,,..;

><

21-

r1 ". .~., .

.... ","

;- =:>~.. ."

" ...

I LSD (5%)

No inoculum Inoculum

8-

6-

+l0P-!"'-

0">4f-

'drlQ)

,,..;><

2f-

pH 6.0

v. : ~ ' .

.. ,:.: ~............:.' ' .. , x'·'. : ""~

,I, •

.c.. ••.. '

-", ..." ,~: ~:.. :. ~

, .,,.' "

- I LSD (5%)

No inoculum Inoculum

Fi g. 6. Responses of white clover to liming, inoculation,and nitrogen.

23

and an N-free nutrient solution of the same composition used in the previous

liming experiment was applied 10 days after emergence. The N-free

nutrient solution was added again prior to the first harvest and after the

first and second harvests.

The experiment ran from 7 November 1980 to. 3 February 1981 and the

clover was harvested three times as in the previous experiments.

Results

Dry matter yields for all three harvests are shown in Fig. 6. Unlimed

clovers (pH 4.8) without inoculum or added nitrogen were N-deficient and

inhibited in growth and many seedlings died within 3-4 weeks of emergence.

Some survived and grew slowly and eventually became nodulated. Inoculated

clovers at pH 4.8 had almost 100% survival and gave yields comparable to

those where 100 ppm nitrogen was added.

Liming to pH 6.0, without inoculum or added nitrogen gave 100% survival

and gave yields comparable to inoculated clovers at pH 4.8. These clovers

were found to be nodulated and were obviously fixing nitrogen. Inoculated

clovers at pH 6.0 produced significantly higher yields than the uninoculated

clovers and yields were comparable to those receiving 100 ppm nitrogen.

Nitrogen in addition to inoculation gave significantly higher yields than

inoculation or nitrogen alone at either pH level.

It may be concluded that good survival of seedlings is obtained from

either inoculation of seed with rhizobia or liming to pH 6.0. However,

for both survival and good growth of white clover, both inoculati~n and

liming of the peat is essential.

DISCUSSION

Laboratory and glasshouse studies have been undertaken on Ruakaka loamy

peat to:

1. Characterise the physical, chemical and fertility properties of

importance to plant growth, and

24

2. Assess the effect of isopropanol extraction on these properties.

Ruakaka loamy peat is a basin peat formed from rushes and ferns under a high

water table where anaerobic conditions have led to the accumulation of organic

matter. Because of their proximity to coastal dune sands they have

accumulated considerable amounts of windblown sand. The bulk sample studied

contained more than 50% fine sand (0.1 _.. 02 mm material) which gives the

peat its loamy characteristics. The peat also contains considerable amounts

of woody material derived from the former kauri forests that colonised the

area.

According to nata given in Appendix A OT tne report oy LuttrlsS,

McKenzie, Martin (1979) the dry bulk density of the unconsolidated peat

averages 0.15 g cm 3 (150 kg m3). Fully saturated with water the peat will

have a moisture content of 600% on a dry weight basis.

Following drainage, mining, extraction, reclamation and consolidation

of the peat the moisture-holding properties and bulk density will markedly

change. The density of peats that were dewatered and sieved « 6 mm) to

remove woody material and consolidated by light tamping for glasshouse pot

experiments averaged 0.58 g cm 3 before extraction and 0.66 g cm 3 after

extraction. These values were similar to those obtained by Cuttriss,

McKenzie and Martin (pers. comm.) using the Procter test. Densities of

around 0.6 g cm 3 are probably higher than those that will be obtained in the

field during reclamation with earthmoving equipment and subsequent treading

with livestock. Furthermore the incorporation of considerable amounts

of comminuted woody material will tend to reduce the bulk density of the

reclaimed peat, so that bulk density values of 0.4 to 0.5 g cm 3 would seem

more likely.

A three-fold increase ln density after drainage and consolidation would

reduce the mean depth of peat from 2.7 metres in the undeveloped state to about

0.9 metres. In developing the reclaimed area for agriculture a depth of

0.75 metres of rooting depth should be regarded as minimum. The materials

25

underlying the peat are compacted sands and these should be scarified

to a depth of 20-30 em and some peat incorporated to break the compacted

layer and to increase permeability. The resultant depth of peat plus

peaty sand would provide an adequate rooting depth not only for pastures

but for horticultural crops as well.

Physical measurements on the peat carried out at a bulk density of

0.6 g cm 3 indicate high water holding capacities (42% by volume) and medium

to high values for plant 'available' water (20% by volume). Isopropanol

extraction had a small but insignificant effect on moisture retention.

However, when the peat was oven-dried moisture holdiHg capacity decreased

and available water dropped to 11% by volume. Since the peat is to be dried

down to a figure of 33% moisture (dry weight basis), no losses of moisture

holding capacity will occur.

Saturated hydraulic conductivities on extracted peat measured at a

density of 0.6 g cm 3 showed low values of 1.8 mm hY- 1 • This work lS now

being repeated at lower densities and it is expected that higher conductivities

will be obtained. Studies are currently in progress to assess the effect

of isopropanol on the wettability of peat dried to different moisture

contents.

Chemical studies showed that the peat is strongly acid, has a high

capacity to retain nutrients and contains adequate amounts of calcium,

magnesium, phosphorus and sulphur, for plant growth. Because of a high

C/N ratio, it is very deficient in nitrogen and the available potassium

content is low.

Isopropanol extraction brought about small decreases in the total carbon,

nitrogen, phosphorus and adsorbed sulphur contents, and an apparent increase

in available calcium and magnesium. These changes are of no great

significance, but these chemical properties should be monitored when

extraction is done on a con~ercial scale.

26

The glasshouse experiments show that nitrogen deficiency 1S the most

important factor limiting ryegrass growth on the peat. To a lesser extent

potassium, magnesium and phosphorus were limiting to growth, although the

response to phosphorus and magnesium did not occur in the extracted peat,

possibly because of a release of these nutrients'during the drying of the peat.

No trace element deficiencies were evident and foliar analysis confirmed

that the supply of copper, manganese, iron and zinc was adequate for good

growth.

Liming experiments indicated that lime was not necessary for ryegrass,

but for white clover liming to pH 5.5 plus inoculation of clover seed with

rhizobium bacteria was necessary for good growth.

In practical terms, estimates of lime and fertiliser rates for

satisfactory establishment of ryegrass/white clover pasture on Ruakaka loamy

peat would be 5-6 tonnes/ha of lime (containing magnesium) to bring the pH

in the top 10 cm of peat to pH 5.3-5.5, about 300 kg/ha of potassic

superphosphate and one or more light applications of urea (100 kg/ha) during

the establishment phase.

Results from the glasshouse and laboratory experiments cannot be

extrapolated directly to the field and field experiments will be needed.

Kauri Deposit Surveys Ltd have indicated their intention to sponsor

Government-based agronomic field trials to ascertain optimum rates of lime

and fertilisers for pasture establishment and maintainance. However,

the laboratory and glasshouse studie~ will provide 3 sound basis for the

planning of meaningful field trials.

CONCLUSIONS

l. Extraction of Ruakaka loamy peat with hot isopropanol does not impair

its water-holding properties providing the moisture content of the

peat prior to extraction is not reduced to low levels.

27

2. Isopropanol extraction does not have any significant detrimental

effect on the nutrient status of the peat and plant growth in the

treated peat was comparable to that in unextracted peat.

3. Ruakaka peat is strongly acid, very nitrogen deficient, but contains

reasonable levels of calcium, magnesium, phosphorus and sulphur.

Trace element uptake by ryegrass was adequate.

4. For ryegrass/white clover pasture establishment, the peats should be

limed to pH 5.3 - 5.5 and fertilised with about 300 kg/ha of potassic

superphosphate and 100 kg/ha of urea. Clover seed should be inoculated

with rhizobium bacteria.

REFERENCES

Andrews, C.S.; Fergus, I.F. 1964: Techniques in plant nutrition and soil

fertility survey. ~ Some concepts and methods in subtropical pasture

research. Commonwealth Bureau of Pastures and Field Crops. G.B.

Bulletin 47, pp.173-185.

Blakemore, L.C.; Searle, P.L.; Daly, B.K. 1972: Methods for chemical

analysis of oils. New Zealand Soil Bureau Scientific Report IDA.

Cuttriss, McKenzie. Martin and Co. 1979: Kauri. resin extraction and land

reclamation project at Kaimaumau, Northland, New Zealand. Report

on project concept and envirollrliental assessment, for Kauri Deposit

Surveys Ltd. 60 pp.

Gladwell, M.W. 1971: Methods for physical analysis of soils. New

Zealand Soil Bureau Report laC.

~lute, A. 1965: Laboratory measurements of hydraulic conducLivity of

saturated soils.

.... p_ •• l~ ... _,.. !l~~-:-'

In C.ft... Black ct al. (ed .. 1. r·Jcthods of soil

28

N.Z. Soil Bureau 1954: General survey of the soils of North Island,

New Zealand. N.Z. Soil Bureau Bulletin 5. 286 pp.

Spencer, Thomas and Associates, Pty. Ltd. 1979: Kauri resin extraction.

Report on investigations at Kaimaumau, Northland, New Zealand, for

Kauri Deposit Surveys Ltd. 68 pp.

ACKNOWLEDGMENTS

The authors gratefully acknowledge the assistance of the following Soil

Bureau staff: C.W. Ross, for carrying out soil moisture measurements;

J. Hunt, for X-ray fluorescence analysis of plant material; Mrs M. Blakemore,

for chemical analysis of peat samples; and Misses K.F. Meyrick and

M.L. de Lautour, for assistance with pot experiments.

LABORATORY AND GLASSHOUSE STUDIES,

ON RUAKAKA LOAMY PEAT

by

J.P. Widdowson and H.M. Watts

Soil Bureau, Department of Scientific and Industrial ResearchLower Hutt, New Zealand

-~~ •••_.... ~~~ ~. .~ -" - ~ "" t......~-~....

INTRODUCTION

Kauri Deposit Surveys Ltd has applied for a'mining licence in order to

drain and systematically mine some 2,200 hectares of peat at Kaimaumau,

Northland, extract the natural resins and subsequently return the extracted

peat to the land to allow reclamation of the area for agricultural use.

Details of the project concept and environmental assessment are given

by Cuttriss, McKenzie and Martin (1979) and information on the extraction of

resins and other products from the Kaimaumau peat deposits is given by

Spencer, Thomas and Associates (1979).

The licence area is situated about 27 k north of Kaitaia with the

northern and eastern part of the area bounded by sandhills and the shoreline

at Rangaunu Bay. The southern and western portion is generally bounded by

farmland, some of which has been reclaimed from the peat swamp. The peat

has an average depth of 2.7 metres, a maximum depth of 5.8 metres and thins

out on the edges and in the vicinity of sand ridges that intersect the

area.

The peat is generally black in colour, well-decomposed and contains

considerable amounts of woody material with relatively few recognisable plant

remains. It is known that kauri forest (Agathis australis) has occupied

the area on at least three separate occasions; the oldest kauri stumps

have been carbon-dated at 41,000 to 38,000 years B.P. The area has been

subjected to gum digging over a long period and the surface is heavily pock­

marked with water-filled holes from this activity.

The soils of the peatlands have been mapped (N.Z. ·Soil Bureau, 1954)

as Ruakaka peaty sandy loam and loamy peat, are poorly drained and are of

low natural fertility.

2

Successful restoration of the mined area for agricultural use,

following extraction of the peat with isopropanol assumes that the extraction

process does not adversely affect the peat as a medium for plant growth.

Studies were therefore undertaken in both laboratory and glasshouse at

Soil Bureau, Lower Hutt, to assess the effects of solvent extraction on

Ruakaka loamy peat as a medium for plant growth. This paper reports the

effects of isopropanol on some physical and chemical properties of the peat

and on the growth and nutrient uptake of ryegrass and white clover grO\VTI

on the peat.

SAMPLE PREPARATION

Two bulk samples of peat were obtained from the Industrial Processing

Division, D.S.I.R. in December 1979. The samples were part of as-tonne

consignment of peat from Area 4 at Kaimaumau, Northland, which had been dried

and sieved at Paraparaumu Airport. One of the samples had been extracted

with isopropanol in the pilot plant of Industrial Processing Division.

Prior to carrying out glasshouse experiments and physical and chemical

analysis, the bulk samples were sieved « 6 mm) and moistened to near field

capacity (~ 70% w/w) and stored In polythene sacks. Samples for chemical

analysis were air-dried and passed through a 2 mm sieve.

WATER HOLDING PROPERTIES

Methods

Sieved samples of Ruakaka loamy peat were packed into brass rlngs

(68.6 cm 3 volume, approx. 5.4 cm diameter x 3 cm long) to an equivalent

dry bulk density of about 0.6 g cm- 3• Moisture release characteristics

were determined using the pressure plate apparatus (hanging water column

and air pressure) for matric potentials do\\~ to -1 bar and a pressure membrane

system was used at -IS bars according to the methods described by Gradwell (1971:

All measurements were

3

Saturated hydraulic conductivities were measured on cores packed as

above using the fixed head method of Klute (1965).

replicated at least three times.

Results

The peat material has high water-holding capacities with 'plant-

available water' contents (water held between -0.2 bars and -15 bars) being

about 34% by weight or 20% by volume (many soils are in the range of 10-20%

by volume). Alcohol extraction has not significantly changed the water

retention characteristics although there is a slight loss of water-holding

ability at, and just drier than, saturation (see Fig. 1). In contrast,

oven-drying the peat has significantly reduced the moisture retention, the

plant available water being approximately 17% by weight or 11% by volume.

This probably results from induced hydrophobic or water repellency conditions

which are commonly observed in dried peat. Some practical ,consequences

of this phenomenon in the field would be slower water infiltration rates

and, therefore, increased surface runoff of rain Kater and poorer water

storage within the peat could result in drought stress for pasture or crops.

Saturated hydraulic conductivities were slow at 1.8 mm hr- 1 for both

the alcohol-extracted and non-extracted peat (dried peat was not tested).

However, this value probably represents the worst possible practical situation

since it was measured using sieved peat \vith all of the coarse, woody material

removed and the compaction to 0.6 g cm- 3 dry bulk density would be a maximum

in the field situation. Tests are underway to examine more realistic values

(i.e., entire samples with lower compaction rates).

CHEMICAL PROPERTIES

Chemical analyses were carried out according to the methods of Blakemore

et al. (1972) on extracted and non-extracted peat samples in order to:

1. Assess the chemical properties of Ruakaka loamy peat.

140

130

120

no

100

~ 90.........~

",0 80~

+Jc:(j) 70+Jc:au 60H(j)+JrU 50~

40

30

20

10

~ Unextracted, non-dried peat

~ Extracted, non-dried peat

~ Extracted, oven-dried peat

a--------__4r---- -=-_._-......,~

1:>.

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Fi g. 1.

Matric potential (bars)

Moisture retention by Ruakaka loamy peat, as affected by alcohol-extraction and drying.

5

"

2. Assess the plant nutrient status of the peat.

3. Assess the effect of isopropanol extraction at 70°C on chemical

properties and nutrient status.

The analyses (Table 1) show that the peat is strongly acid (pH 4.1) and

contains about 46% (w/w) organic matter. pH vaiues made on air-dried

samples are normally 0.5 pH units lower than values obtained on field moist

samples. The peat has a high CIN ratio - a characteristic which reflects

a high proportion of plant residues, particularly woody and fibrous material.

Peats and organic soils with C/N ratios of 30 or more will immobilise

mineral nitrogen causing the soil medium to be nitrogen deficient.

The peat has a high cation exchange capacity which is a measure of the

ability of the peat to retain the nutrients calcium, magnesium, potassium

and sodium against leaching. As a medium for plant growth, the peat is

strongly acid but contains adequate amounts of calcium, magnesium, phosphorus

and sulphur. Nitrogen is likely to be very deficient and potassium is

likely to be limiting especially under intensive cropping.

Extraction of the peat with isopropanol has affected some of the

chemical properties of the peat. There has been a decrease in organic

carbon, nitrogen, total phosphorus and adsorbed sUlphur contents. On the

other hand, there has been an increase in total exchangeable cations viz.

calcium and magneslum. An explanation for the increase in exchangeable

calcium and magnesium is that isopropanol, being non-ionic, is unable to

desorb any exchangeable calcium and magnesium. But because the isopropanol

is removing resins and waxes from the peat which are essentially inert with

respect to the cations calcium and magnesium, there is a relative increase

in concentration. The small decreases in available phosphorus (Truog P),

exchangeable potassium and sodium are of little significance.

Isopropanol therefore in removing resins, waxes and other extractables

does remove some carbon, nitrogen, phosphorus and SUlphur from the peat,

but has little effect on the exchangeable cations; in fact it appears

to give a relative increase in calcium and magnesium. Water-soluble

Table 1.

6

Chemical properties of Ruakaka loamy peat.

Property Non-extracted IsopropanolExtracted

pH 4.1 4.4

Carbon % 27.1 21. 8

Nitrogen % 0.30 0.26

C/N 90 84

Total phosphorus (mg %) 41 33

Truog phosphorus (mg %) 10 9

Adsorbed sulphur (ppm) 138 129

Cation exchange capacity (me %) 73.4 74.0

Exchangeable calcium (me %) 14.6 20.2

Exchangeable magnesiwn (me %) 1. 20 1. 35

Exchangeable potassiwn (me %) 0.25 0.24

Exchangeable sodium (me %) 0.43 0.39

Total cations 2: (me %) 16.5 22.2

Base saturation (%) 22 30 .

7

Table 2. Ratings for chemical pl"opcrties

The following ratings for chemical properties are usedby Soil Bureau for New Zealand soils:

Phosphorus p Adsorbedretention' S04

Rating Truog 0.51'.1 H2 SO4 (%) (ppm 5)

(mg %) (mg %)

Very high > 5 > 40 90-100 > 150. ,

High 3-5 20-40 60-90 50-150

Medium 2-3 10-20 30-60 15-50

Low 1-2 5-10 10-30 5-15

Very low < -1 < 5 0-10 < 5

Rating Organic C Total N C/N pH (1:2.5 soil:water)(%) (%)

Very high > 20 >1.0 > 24 ) > 9.0 (extremely alkaline)) 8.4-9.0 (strongly " )) 7.6-8.3 (moderately " )

High 10-20 0.6-1.0 16-24 ) 7.1-7.5 (slightly· II )) 6.6-7.0 (near neutral)

Medium 4-10 0.3-0.6 12-16 ) 6.0-6.5 (slightly acid)) 5.3-5.9 (moderately II )

LO\'1 2-4 0.1-0.3 10-12 4.5-5.2 (strongly " )Very 10\'/ 2 < 0.1 <10 < 4.5 (extremely " )

Cation-Exchange Properties

Rating CEC L Cat BS Ca Mg K Na(me.%) (me.%) (%) (me.%) (me.%) (me.%) (me.%)

Very high > 40 > 25 80-100 > 20 > 6 > 1.2 > 2

High 25-40 15-25 60-80 10-20 3·:6 0.8-1.2 0.7-2

Medium 12-25 7-15 40-60 5-10 1-3 0.5-0.8 0.3-0.7

Low 6-12 3-7 20-40 2-5 0.3-1 0.3-0.5 0.1-0.3

Very low < 6 < 3 <: 20 < 2 < 0.3 <: 0.3· <: 0.1

8

nutrients, such as nitrate nitrogen, would be ~xtracted by isopropanol,

but the amounts present in an acid peat would be negligible.

GLASSHOUSE EXPERIMENTS- ,

Pot experiments under glasshouse conditions were carried out to assess

the nutrient status of Ruakaka peat both before and after extraction with

isopropanol using perennial ryegrass as the test plant. Since both

experiments showed yield depressions when the peats were limed to pH 5.5,

further experiments with both perennial ryegrass and white clover were

carried out to assess the yield response to lime over a range of pH values.

Finally, the effects of liming, inoculation with rhizobium bacteria and

nitrogen on white clover growth \"ere examined in a factorial pot trial.

EXPERIMENT I. Nutrient status of peat before and after extraction with

isopropanol.

Methods

Ryegrass Lolium perenne was grown in 15 cm plastic pots containing the

moist equivalent of 660 g of oven-dry sieved « 6 mrn) peat for three months

under glasshouse conditions. In this experiment the response of ryegrass

to lime and the nutrients nitrogen, phosphorus, potassium, sulphur,

magnesium, iron, copper, zinc, manganese, and boron was examined using a

llsubtractive ll technique (Andrews and Fergus, 1964). In the "subtractive"

technique treatments were applied by supplying all nutrients needed for

plant growth except one and a complete nutrient treatment in which all

nutrients are added to the soil. In a subtractive treatment ryegrass is

dependent on the peat for its supply of that nutrient that has been omitted

and the extent to which growth is 1imi ted provides a mea-sure of the

adequacy or deficiency of that particular nutrient.

9

Lime (at 8.0 g CaC0 3 per pot) and phosphorus (0.25 g Ca(HZ

P04)z per

pot) were mixed into the peat prior to potting, whereas all other nutrients

were applied in sOlution after emergence of ryegrass and again after each

harvest. The total quantities of nutrients (mg) applied to each pot,

during the experiment were: N, 404; P, 66.2; K, 376; S, 104; Mg, 76;

Ca,3588; Fe,10.6; Cu,12.8; Zn,11.2; Mo,2.0; Mn, 36.8 and B, 7.2.

The experiment was run in two parts. The unextracted peat experiment

ran from 22 February to 15 May and the extracted peat experiment ran from

8 July to 8 October 1980, in a glasshouse maintained between 18 and 26°C.

Distilled water was added regularly to adjust soil moisture content to field

capacity. Three harvests were made at 3-4 weekly intervals and the

harvested material was dried at lODC and weighed. Dried material from

the third harvest was ground in a Tema mill, pressed into discs and

analysed for both major and minor nutrients by X-ray fluorescence spectro-

graphy.

Results

Unextracted peat

Dry matter yields over three harvests, given in Fig. 2, showed that on

unextracted peat nitrogen, phosphorus and magnesium were limiting for the

growth of ryegrass. A severe nitrogen deficiency is clearly the most

important factor limiting growth, a result which was predicted from the

high C/N ratio of this peat. lfuile phosphorus is shown to be limiting

for optimum growth, the presence of high values of Truog P in the peat,

together with a phosphorus concentration of 0.30% (Table 3) in ryegrass

leaves at the third harvest, indicates that phosphorus is not markedly

deficient. It would appear that under glasshouse conditions which were

favourable for good growth of ryegrass, the rate of phosphorus supply to

plant roots was below optimum.

The response to added magnes1urn 1S considered to be due to the

correction of an imbalance between exchangeable calcium and magnesium

'tJ..-IQJ

-rl><01°

100

80

60

40

20

* *'- -

---r-

r- r--..--

*r-

*r-

.

* *fj r-l

* Denotes significantdifference (at 5% level)from 'c' treatment.

o

c -N -p -K -S -Mg -Fe -Cu -TE -L o

Fi g. 2.

Subtrac,tive treatments

Dry matter yields from unextracted peat (expressed as percentage of'complete' treatment).

'1jH(!)

•.-1><",0

10

8

6

4

2

- r-.....--: 1- r--r-

r--r-

,-,

* * Denar---

diff, froIT

* * *.---. ~ .---.

tes significanterence (at 5% level)

'c' treatment.

......

c -N -p -K -S -Mg -Fe -Cu -TE -L O+L o

Fi g. 3.

Subtractive treatments

Dry matter yields from extracted peat (expressed as percentage of'complete' treatment).

Table 3. Element content of ryegrass from unextracted peat at harvest 3.

Sample % ppmCa K Cl S P Si Al ~1g Na Mn Fe Cu Zn

C 1. 01 4.12 0.88 0.42 0.29* 0.28 0.01 0.28 0.13 273 93 9 66

-p 1. 17 3.96 0.78 0.41 0.30* 0.44 0.01 0.28 0.15 305 145 10 68

-K 1. 08 0.56* 0.74 0.38 0.33 0.38 0.02 0.40 2.59 294 137 10 74

-S 1.16 3.88 1.12 0.42 0.30* 0.36 0.21 0.30 0.15 313 118 10 72

-Mg 1. 04 3.66 0.70 0.40 0.34 0.35 0.007 0.23 0.37 285 107 10 76

-Fe 1. 04 3.94 0.80 0.42 0.31 0.31 0.01 0.30 0.10 305 101 10 75

-Cu 0.98 3.94 0.79 0.42 0.31 0.32 0.01 0.26 0.11 294 101 6 65

-TE 0.96 3.71 0.74 0.43 0.26-k 0.21 0.01 0.30 0.19 128 109 8 41

-L 0.78 3.86 0.87 0.41 0.35 0.24 0.01 0.26 0.14 303 116 10 82

Critical0.2 1.7 0.2 0.24 0.30 0.13 0.05 20 40 4 10Level - -

* Deficient

.......N

Table 4. Element content of ryegrass from extracted peat at harvest 3.

Sample% ppm

Ca K C1 S P Si Al Mg Na Mn Fe Cu Zn

C 0.79 3.32 0.75 0.64 0.41 0.18 0.003 0.33 0.35 248 76 7 60

-p 0.77 3.36 0.93 0.57 0.31 0.20 0.005 0.33 0.39 243 83 7 84

-K 0.74 0.49* 1.08 0.57 0.54 0.24 <0. 003 0.37 2.44 269 76 8 67

-S 0.86 3.41 2.36 0.38 0.42 0.20 <0. 003 0.33 0.39 233 80 8 58

-~1g 0.77 3.36 0.67 0.65 0.37 0.18 <0.003 0.28 0.55 222 74 8 61

-Fe 0.79 3.44 0.70 0.62 0.43 0.20 <0.003 0.35 0.35 262 76 7 57

-Cu 0.78 3.41 0.69 0.65 0.42 0.19 <0.003 0.31 0.33 250 79 7 59

-TE 0.79 3.37 0.42 0.69 0.41 0.18 <0.003 0.33 0.41 188 72 7 56

-L 0.72 3.43 0.94 0.72 0.39 0.19 <0.003 0.35 0.38 223 78 8 51

Critical 0.2 1.7 0.2 0.24 0.30 0.13 0.05 20 40 4 10level - -

* Deficient

Vl

14

that would be aggravated by liming with pure calcium carbonate. Ryegrass

yields were greater in the absence of lime than where it had been added.

Although the peat is acid it does contain adequate amounts of calcium

for good growth and it is likely that soluble aluminium, which usually

restricts growth in acid mineral soils with pH values less than 5.0, is

not a problem in these peats. The depression to liming was therefore

considered to be due to a reduction in the availability of trace elements.

However, trace element contents of ryegrass leaves from the third harvest

(Table 3) shows that levels of manganese, iron, copper and zinc ln the

presence of added lime are adequate for plant growth.

The significant depression in yield due to the addition of the trace

elements zinc, boron and manganese has been shown to be due to an excess

amount of boron added to the peat. Ryegrass receiving boron treatment

showed a browning of the tips of older leaves and excess concentrations

of boron \.,Jere found in the leaves.

Extracted peat

Dry matter yields over three harvests, given in Fig. 3, showed that on

the extracted peat a severe deficiency of nitrogen, and a slight deficiency

of potassium were limiting ryegrass growth. Compared with the unextracted

peat, no deficiency of phosphorus or magnesium were observed. Because it

was shoh~ in the discussion on the chemical properties of peat before and

after extraction that isopropanol had little effect on the nutrient status

of the peat, the differences in ryegrass growth were unexpected. Two

factors may have affected the results obtained. The experiment on the

extracted peat was carried out at a different time of the year when initial

growth rates of ryegrass were slower due to shorter day-length. Under

these conditions of slower growth, the demand for both phosphorus and magnesium

by the ryegrass would be l~ss and hence no depression in growth was obtained

in the minus phosphorus and magnesium treatments. The other factor which

may have contributed was that prior to the experiment the extracted peat

]S

was oven-dried to remove residues of isopropanol that were present 1n the

sample obtained from the extraction plant. The effect of oven-drying has

probably resulted in some mineralisation of organic matter which has

increased the availability of phosphorus and magnesium in the growing medium.

No depression was obtained to the addition of trace elements as a

result of reducing the amount of boron added to one quarter of that added

to the unextracted peat. Nor was there any depression in ryegrass yield

from the addition of lime. Because of the inconsistencies in the response

to lime added to peat, further work was undertaken.

The element content of ryegrass leaves from the third harvest (Table 4)

indicates adequate levels of both major and trace elements.

EXPERIMENT 2. Responses to ryegrass and white clover to liming on

Ruakaka loamy peat.

Methods

Pot trials were carried out to assess the optimum pH for ryegrass

and white clover growth on unextracted Ruakaka loamy peat in the absence

and presence of added trace elements.

1. Ryegrass

Prior to potting up, lime was added at the rate of 0, 2.68, 5.35, 8.03

and 13.38 g A.R. CaC03

to the moist equivalent of 670 g oven-dry sieved

« 6 mm) unextracted peat and allowed to equilibrate for 14 days.

After 14 days the pH values on the liming treatments were 4.81, 5.27,

5.69, 6.02 and 6.39. Prior to planting, Ca(H2P0

4)2 at the rate of

100 ppm P was mixed throughout all soils. Ryegrass was sown into

15 cm plastic pots and after emergence the trace element treatments

were factorially applied to the pots along with a nutrient solution

which supplied N, K, S, Ca and Hg. Trace element treatments and

basal major nutrients were applied again prior to the first harvest of

ryegrass and again after the first and second harvests. The total

quantities of nutrients (mg) supplied were identical to those used in

16

the subtractive experiments with boron reduced to 1.40 mg per

pot. There were three replications and the layout was a randomised

complete block.

The experiment ran from 4 August to 26 November 1980 in a glasshouse

maintained at 18°-26°C and soil moisture was adjusted regularly to

field capacity with distilled water: The ryegrass was harvested three

2.

times at 3-4 weekly intervals and the harvested material was dried at

70 0 e and weighed.

White clover

In this experiment, identical rates of lime and trace elements were used

as in the ryegrass liming experiment. White clover was sown into IS em

plastic pots containing the moist equivalent of 640 g oven-dry sieved

« 6 rnrn) unextracted peat that had received lime and phosphate prior

to potting. Fourteen days after sowing the clover seedlings were

inoculated with a suspension of rhizobium bacteria. Two \I'eeks later

the trace element treatment was applied factorially together with

nutrient solution which supplied K, S, Ca and Mg tQ all pots. Trace

element treatments and basal major nutrients were applied again prior to

first harvest and again after first and second harvests. Apart from

nitrogen, which was omitted from the white clover experiment, the total

amounts of nutrients applied were identical to those used in the

subtractive experiments. There were three replicates arranged in

randomisedcomplete blocks. The experiment ran from 16 September 1980

to 13 January 1981 and was maintained under the same conditions as the

ryegrass experiment.

Results

1. Ryegrass

Dry matter yields for the three harvests are sho\~~ in Fig. 4. Over the

whole experiment ryegrass yields decreased significantly with liming

.woo."­tJ1

'dr-fQJ

-rl>,

10-1QJ.w.wrUE>,10-1Q

9 -

8 -

7 -

6 -

5 -

4 -

3 -

2 -

1 -

r-~'1·"

· ~ ~:'''::'..~'>.l-:' .. "."J/:(, ~ .. "t-,I ," ~ "

:'I'~~(

"!'\"~::::"~~ ',,'~' .. 'I)'~ 1 'I "1'.1.,',,. .:1:',..'":;:~~ ~.

tsJ I'r,

· \I;,~ :',

':ist '.1.1

t··- .!•• >'\ .....'I~'"..... ,

~~ ..·.~ .

".\','",'f,;;:.1.\.~ .~r"",1:" \~~,;~: ".'\":!~

4.8

r-l-.... 1 ... , ~

,! :-:.:

: ~, ;,' ::'....' '~.';.,.',:.:',',: :;,

I .~, •

,~" ~:,

:::' ~.,.". :....\',.. ' ~

::.'oJ,',".'.',:~,l·,":',".,,~It:' ,t'

.'.""f :~,~.:" .".1-'.~~ J ,

~: ..\\:,e ."

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

~ , I"

.{;:;;"t'"\ '1'"\ ',.1',, ,I,'

q .J.... IX··',' r ~,!I., I

",I: ".::/ i~\

I/'''~~ ~J;1''1', ".'"

5.3

r--f...,...­r~\ 'l' ", "., .I.,'"I"" ..~," I

.1;' ~

':.1';'1:','J; :,~ ,:'..: ~ '". ~.",' .,,,\.:"

. '..~ :~

'. "\.' .. ',"","~," .'.1,I,~;' ,:

'. \' I

.:~:~',..1.

': ,\,:r"";

. .~

'.'a"• 'J'

\, "~I • \'

\' ~ \,'

.; '. 1.~ ':.~". "", ...

:~.:\ ~~:

'"., ..•: :;', ,.;

5.7

pH

r---

~.<\I"\.:",

'!'f\,,":(,~ I .

~~<:~'\:\,

\", ,

~:~~<'1>'",,I,. ,\'~.' ~; ,. ~ ,,\.. :.""':, '0".' .\~"'rl,~ "

" J\· .I\~.1_ •,,'.'';. t'·... ' ~,,\. ~

\',.:..,

:<'~~.~ ,.,",.. '~ ~. I

• • h~ ': ;

\' ~ ;:.,.,\

, ',",\1 1 \'

:.'t·.,: .'

~.}.1 ~\"

6.0

r-

~~:t ,......., 'I

1"".

.~.::/}.. ,:, ~ '.:;:, ..

. 'I"

\, 'M.~.""

.'~ ': ::l't l,'

:'1'~ J,\".··.·:.(.l''.:.1

'~'.II,':~~:;

:/.:~.'. ' ..\: ...I"::,:"', ','

/ '..I' • .,

'1".-',

;(>:'~~';~'~ ..', ..~ .. ' ~

6.4

c=J No trace elements

l):f~l Trace elements added

I LSD (5%)

-..J

Fi g. 4. Responses of perennial ryegrass to liming.

Table 5. Element content of ryegrass as affected by trace elements,and 1iming.

pH Trace % ppmelements P K Mg Ca Mn Fe Cu Zn

4.8 TO 0.46 4.72 0.25 0.84 111 86 8 35

T10.44 4.84 0.26 0.81 189 88 12 58

5.3 TO 0.42 4.90 0.25 0.77 107 92 8 44

Tl

0.43 4.81 0.26 0.83 176 88 11 53

5.7 TO 0.40 4.80 0.23 0.83 100 92 8 46

Tl0.43 4.84 0.23 0.83 165 88 11 54

6.0 TO 0.38 4.72 0.24 0.84 77 91 8 47

Tl

0.39 4.79 0.23 0.82 147 90 11 SO

6.4 TO 0.33 4.63 0.22 0.89 51 95 8 48

Tl0.31 4.57 0.24 0.93 96 97 10 45

Critical level 0.30 1.7 0.13 0.20 20 40 4 10

00

19

and with addition of trace elements. Total yields at S.7 and 6.0

were significantly less than those at pH 4.8 and 5.3; likewise, yields

at pH 6.4 were significantly lower than those at pH 6.0.

A depression to liming is normally associated with reduced plant

availability of trace elements at higher pH'levels. However, those

element levels shown for the first harvest material (Table 5) indicate

satisfactory element contents over all pH values and only phosphorus

and manganese are sho\m to decrease with increasing pH.

The decrease in ryegrass yield with addition of trace elements

cannot be explained from the element contents shown in Table 5. The

content of manganese, copper and zinc were increased by the addition

of trace elements but In no instance are these levels excessive for

ryegrass growth. It is possible, however, that boron uptake (results

not available) may have been excessive in the trace element treatments.

From this experiment we may conclude that neither liming nor

trace element addition is beneficial for ryegrass growth on this peat.

2. h~ite clover

Dry matter yields for the three harvests are sho~~ in Fig. 5. Over

the whole experiment clover yields increased significantly with liming,

with near maximum yields being obtained at pH 5.7. Trace element

addition appears to increase clover yields at pH 4.8 and 5.3, but

these differences were not significant. Pale leaf colours in clovers

at pH 4.8 and 5.3 during the establishment phase suggested that

inoculation may not have been fully effective. The interaction of

liming, inoculation and added nitrogen was therefore investigated

in a later trial.

From this experiment we can conclude that liming to near pH 5.7

will produce optimum yields of white clover.

c=J No trace elements

9-

8 -

7 -

~

-IJ0 6-0.,"-0'

'0 5 -.--iQ)

'"><~ 4 -Q)-IJ-IJnjE

>< 3-~Cl

2-

1-

1-,-,~,

'If"1, .'1~ , ..'< ,j

r-1X~.,;\", '}'/1/1,,:, I, I,'" .. ;.,.';\"\':.\'

" 1:,\'. ~':7::\:," J I

. I;....:I' ,~.'\~.

'. '" I

"';'.'l.: .'I~:":.\ ..":'J. ,'t

:~:;.~~~:~. ';',; '.: ~il" :(

... ~ "......."" ... :{''":

4.8

r-;""":",'-

~;.\~~ ,I;"

~:,,~

.' " '-:,.\1.,

,...--.

',r:'~.,.' t''0','','.. ::\','I: ~(~

~ I 'I'"

" 0".. ,,~ .'~ ..", ,\', ,

I ~ ',.1.~ ...... ,¥

',J.;",".\,':'. ,'.• 10"

.:': .',',,'

.' , '" ~ i

:~\:.:, ;',, I~, ~',':,,!",\0-''';

5.3

":,",'\" ~. ,:I";: .,~,~ .

.~:.,~:-

', ..'" ..

::'f'::::~'~1',,'

.~. ,. ". ......... /.'

~·S·::·Ill' '~':.. t"~~~>t

:'., :,',

5.7

pH

t-"'-

~': . \ ..~, (:.

::'::~,:•~ j' ~,:

~ \~'\'','. t\, I::.~.:- .. ",

\ \,:,:;<:'~1.

"1" ..:(1'.. : .'..t.· ,,'1:\•.:

~:'~:''::;:::.':',::;"', .•,J

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

r~:). \,,\,

,.1,\".. ' ,'. ~,\;:

";';':".' ~ ,:,.'{,;;."l.'..',

~j\:,/0,'

''.,\.,"', ol..

1"\,.\',J. I.

\ :'" ~

6.0

,t:~~~.l L~

.:,:~ ;,,~,:.....~. .', ....: s;.. .

<":'\!~':,".' !...~, ,, .\.,\'.1 )" .'t.~;''';\~. \';,:

.-,' \

>~~:)"~Vj'·I!',·

'1""""" I\' ;,,.'•• 1 ' •) .... i:

;I~\~.~,",',:'", ......~~ ',\:::~:~,

'.~:)~:.,1~..;..,'

::},~," ...

<:;';,j:'~': ::•• ' I,~

6.4

ill! Trace. "It

ILSD

elements added

(5%)

1'0o

Fi g. 5. Responses of white clover to liming.

EXPERIMENT 3.

21

Response to lime, inoculation and nitrogen In white

clover.

Acid Ruakaka loamy peat, with a high C/N ratio is an inhospitable

medium for clover growth. In general, clovers germinating in such soils

will not survive for long unless infected and coionised by root nodule

bacteria (rhizobia). The rhizobia penetrate the roots of young clover

seedlings and stimulate the host plants to form nodules. In these nodules

colonies of bacteria provide clovers with nitrogenous compounds, synthesised

from free nitrogen present in the soil atmosphere.

l\~ite clover normally responds to liming of acid peats because of the

sensitivity of the rhizobia to acid soil conditions. Because white clover

in the previous liming experiment appeared to establish slowly in the unlimed

treatment (pH 4.8) further work was carried out to examine the effects of

inoculation and liming of white clover in the presence and absence of

added nitrogen.

Methods

The three factors examined were:

1. Lime: 0 and 7.93 g CaC03/pot to give pH values of 4.8 and 6.0.

2. Inoculation: No inoculation and inoculation with a suspension of

Rhizobium trifolii obtained from a commercial culture

"Nitrogerm".

3. Nitrogen a and 100 ppm nitrogen as NaNO applied In solution to3

seedlings 8 days after emergence.

The experiment was a 2 x 2 x 2 factorial with two replications in a

completely random layout. Lime was mixed throughout the soils 14 days before

sowing and a basal application of Ca(H PO) at 100 ppm P was mixed into the2 4 2

peat prior to potting.

lfuite clover was sown into 15 cm plastic pots containing the moist

equivalent of 640 g of oven-dry peat. The inoculum was applied to the seed

at sowing. Nitrogen was applied in solution 8 days after seedling emergence

8

22

~\" ,.",'• c.". I'

,,:0.' .pH 4.8

6-

+l00.."'-0">

4'-'drlQJ

,,..;

><

21-

r1 ". .~., .

.... ","

;- =:>~.. ."

" ...

I LSD (5%)

No inoculum Inoculum

8-

6-

+l0P-!"'-

0">4f-

'drlQ)

,,..;><

2f-

pH 6.0

v. : ~ ' .

.. ,:.: ~............:.' ' .. , x'·'. : ""~

,I, •

.c.. ••.. '

-", ..." ,~: ~:.. :. ~

, .,,.' "

- I LSD (5%)

No inoculum Inoculum

Fi g. 6. Responses of white clover to liming, inoculation,and nitrogen.

23

and an N-free nutrient solution of the same composition used in the previous

liming experiment was applied 10 days after emergence. The N-free

nutrient solution was added again prior to the first harvest and after the

first and second harvests.

The experiment ran from 7 November 1980 to. 3 February 1981 and the

clover was harvested three times as in the previous experiments.

Results

Dry matter yields for all three harvests are shown in Fig. 6. Unlimed

clovers (pH 4.8) without inoculum or added nitrogen were N-deficient and

inhibited in growth and many seedlings died within 3-4 weeks of emergence.

Some survived and grew slowly and eventually became nodulated. Inoculated

clovers at pH 4.8 had almost 100% survival and gave yields comparable to

those where 100 ppm nitrogen was added.

Liming to pH 6.0, without inoculum or added nitrogen gave 100% survival

and gave yields comparable to inoculated clovers at pH 4.8. These clovers

were found to be nodulated and were obviously fixing nitrogen. Inoculated

clovers at pH 6.0 produced significantly higher yields than the uninoculated

clovers and yields were comparable to those receiving 100 ppm nitrogen.

Nitrogen in addition to inoculation gave significantly higher yields than

inoculation or nitrogen alone at either pH level.

It may be concluded that good survival of seedlings is obtained from

either inoculation of seed with rhizobia or liming to pH 6.0. However,

for both survival and good growth of white clover, both inoculati~n and

liming of the peat is essential.

DISCUSSION

Laboratory and glasshouse studies have been undertaken on Ruakaka loamy

peat to:

1. Characterise the physical, chemical and fertility properties of

importance to plant growth, and

24

2. Assess the effect of isopropanol extraction on these properties.

Ruakaka loamy peat is a basin peat formed from rushes and ferns under a high

water table where anaerobic conditions have led to the accumulation of organic

matter. Because of their proximity to coastal dune sands they have

accumulated considerable amounts of windblown sand. The bulk sample studied

contained more than 50% fine sand (0.1 _.. 02 mm material) which gives the

peat its loamy characteristics. The peat also contains considerable amounts

of woody material derived from the former kauri forests that colonised the

area.

According to nata given in Appendix A OT tne report oy LuttrlsS,

McKenzie, Martin (1979) the dry bulk density of the unconsolidated peat

averages 0.15 g cm 3 (150 kg m3). Fully saturated with water the peat will

have a moisture content of 600% on a dry weight basis.

Following drainage, mining, extraction, reclamation and consolidation

of the peat the moisture-holding properties and bulk density will markedly

change. The density of peats that were dewatered and sieved « 6 mm) to

remove woody material and consolidated by light tamping for glasshouse pot

experiments averaged 0.58 g cm 3 before extraction and 0.66 g cm 3 after

extraction. These values were similar to those obtained by Cuttriss,

McKenzie and Martin (pers. comm.) using the Procter test. Densities of

around 0.6 g cm 3 are probably higher than those that will be obtained in the

field during reclamation with earthmoving equipment and subsequent treading

with livestock. Furthermore the incorporation of considerable amounts

of comminuted woody material will tend to reduce the bulk density of the

reclaimed peat, so that bulk density values of 0.4 to 0.5 g cm 3 would seem

more likely.

A three-fold increase ln density after drainage and consolidation would

reduce the mean depth of peat from 2.7 metres in the undeveloped state to about

0.9 metres. In developing the reclaimed area for agriculture a depth of

0.75 metres of rooting depth should be regarded as minimum. The materials

25

underlying the peat are compacted sands and these should be scarified

to a depth of 20-30 em and some peat incorporated to break the compacted

layer and to increase permeability. The resultant depth of peat plus

peaty sand would provide an adequate rooting depth not only for pastures

but for horticultural crops as well.

Physical measurements on the peat carried out at a bulk density of

0.6 g cm 3 indicate high water holding capacities (42% by volume) and medium

to high values for plant 'available' water (20% by volume). Isopropanol

extraction had a small but insignificant effect on moisture retention.

However, when the peat was oven-dried moisture holdiHg capacity decreased

and available water dropped to 11% by volume. Since the peat is to be dried

down to a figure of 33% moisture (dry weight basis), no losses of moisture

holding capacity will occur.

Saturated hydraulic conductivities on extracted peat measured at a

density of 0.6 g cm 3 showed low values of 1.8 mm hY- 1 • This work lS now

being repeated at lower densities and it is expected that higher conductivities

will be obtained. Studies are currently in progress to assess the effect

of isopropanol on the wettability of peat dried to different moisture

contents.

Chemical studies showed that the peat is strongly acid, has a high

capacity to retain nutrients and contains adequate amounts of calcium,

magnesium, phosphorus and sulphur, for plant growth. Because of a high

C/N ratio, it is very deficient in nitrogen and the available potassium

content is low.

Isopropanol extraction brought about small decreases in the total carbon,

nitrogen, phosphorus and adsorbed sulphur contents, and an apparent increase

in available calcium and magnesium. These changes are of no great

significance, but these chemical properties should be monitored when

extraction is done on a con~ercial scale.

26

The glasshouse experiments show that nitrogen deficiency 1S the most

important factor limiting ryegrass growth on the peat. To a lesser extent

potassium, magnesium and phosphorus were limiting to growth, although the

response to phosphorus and magnesium did not occur in the extracted peat,

possibly because of a release of these nutrients'during the drying of the peat.

No trace element deficiencies were evident and foliar analysis confirmed

that the supply of copper, manganese, iron and zinc was adequate for good

growth.

Liming experiments indicated that lime was not necessary for ryegrass,

but for white clover liming to pH 5.5 plus inoculation of clover seed with

rhizobium bacteria was necessary for good growth.

In practical terms, estimates of lime and fertiliser rates for

satisfactory establishment of ryegrass/white clover pasture on Ruakaka loamy

peat would be 5-6 tonnes/ha of lime (containing magnesium) to bring the pH

in the top 10 cm of peat to pH 5.3-5.5, about 300 kg/ha of potassic

superphosphate and one or more light applications of urea (100 kg/ha) during

the establishment phase.

Results from the glasshouse and laboratory experiments cannot be

extrapolated directly to the field and field experiments will be needed.

Kauri Deposit Surveys Ltd have indicated their intention to sponsor

Government-based agronomic field trials to ascertain optimum rates of lime

and fertilisers for pasture establishment and maintainance. However,

the laboratory and glasshouse studie~ will provide 3 sound basis for the

planning of meaningful field trials.

CONCLUSIONS

l. Extraction of Ruakaka loamy peat with hot isopropanol does not impair

its water-holding properties providing the moisture content of the

peat prior to extraction is not reduced to low levels.

27

2. Isopropanol extraction does not have any significant detrimental

effect on the nutrient status of the peat and plant growth in the

treated peat was comparable to that in unextracted peat.

3. Ruakaka peat is strongly acid, very nitrogen deficient, but contains

reasonable levels of calcium, magnesium, phosphorus and sulphur.

Trace element uptake by ryegrass was adequate.

4. For ryegrass/white clover pasture establishment, the peats should be

limed to pH 5.3 - 5.5 and fertilised with about 300 kg/ha of potassic

superphosphate and 100 kg/ha of urea. Clover seed should be inoculated

with rhizobium bacteria.

REFERENCES

Andrews, C.S.; Fergus, I.F. 1964: Techniques in plant nutrition and soil

fertility survey. ~ Some concepts and methods in subtropical pasture

research. Commonwealth Bureau of Pastures and Field Crops. G.B.

Bulletin 47, pp.173-185.

Blakemore, L.C.; Searle, P.L.; Daly, B.K. 1972: Methods for chemical

analysis of oils. New Zealand Soil Bureau Scientific Report IDA.

Cuttriss, McKenzie. Martin and Co. 1979: Kauri. resin extraction and land

reclamation project at Kaimaumau, Northland, New Zealand. Report

on project concept and envirollrliental assessment, for Kauri Deposit

Surveys Ltd. 60 pp.

Gladwell, M.W. 1971: Methods for physical analysis of soils. New

Zealand Soil Bureau Report laC.

~lute, A. 1965: Laboratory measurements of hydraulic conducLivity of

saturated soils.

.... p_ •• l~ ... _,.. !l~~-:-'

In C.ft... Black ct al. (ed .. 1. r·Jcthods of soil

28

N.Z. Soil Bureau 1954: General survey of the soils of North Island,

New Zealand. N.Z. Soil Bureau Bulletin 5. 286 pp.

Spencer, Thomas and Associates, Pty. Ltd. 1979: Kauri resin extraction.

Report on investigations at Kaimaumau, Northland, New Zealand, for

Kauri Deposit Surveys Ltd. 68 pp.

ACKNOWLEDGMENTS

The authors gratefully acknowledge the assistance of the following Soil

Bureau staff: C.W. Ross, for carrying out soil moisture measurements;

J. Hunt, for X-ray fluorescence analysis of plant material; Mrs M. Blakemore,

for chemical analysis of peat samples; and Misses K.F. Meyrick and

M.L. de Lautour, for assistance with pot experiments.