edta-extractable copper, zinc, and manganese in soils of the canterbury plains

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This article was downloaded by: [Stony Brook University] On: 31 October 2014, At: 00:37 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK New Zealand Journal of Agricultural Research Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tnza20 EDTA-extractable copper, zinc, and manganese in soils of the Canterbury Plains R. G. McLaren a , R. S. Swift a & B. F. Quin b a Department of Soil Science , Lincoln Coilege , Canterbury , New Zealand b Ministry of Agriculture and Fisheries , Private Bag, Wellington , New Zealand Published online: 14 Feb 2012. To cite this article: R. G. McLaren , R. S. Swift & B. F. Quin (1984) EDTA-extractable copper, zinc, and manganese in soils of the Canterbury Plains, New Zealand Journal of Agricultural Research, 27:2, 207-217, DOI: 10.1080/00288233.1984.10430423 To link to this article: http://dx.doi.org/10.1080/00288233.1984.10430423 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

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Page 1: EDTA-extractable copper, zinc, and manganese in soils of the Canterbury Plains

This article was downloaded by: [Stony Brook University]On: 31 October 2014, At: 00:37Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office:Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

New Zealand Journal of Agricultural ResearchPublication details, including instructions for authors and subscriptioninformation:http://www.tandfonline.com/loi/tnza20

EDTA-extractable copper, zinc, and manganesein soils of the Canterbury PlainsR. G. McLaren a , R. S. Swift a & B. F. Quin ba Department of Soil Science , Lincoln Coilege , Canterbury , New Zealandb Ministry of Agriculture and Fisheries , Private Bag, Wellington , New ZealandPublished online: 14 Feb 2012.

To cite this article: R. G. McLaren , R. S. Swift & B. F. Quin (1984) EDTA-extractable copper, zinc, andmanganese in soils of the Canterbury Plains, New Zealand Journal of Agricultural Research, 27:2, 207-217, DOI:10.1080/00288233.1984.10430423

To link to this article: http://dx.doi.org/10.1080/00288233.1984.10430423

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”)contained in the publications on our platform. However, Taylor & Francis, our agents, and ourlicensors make no representations or warranties whatsoever as to the accuracy, completeness, orsuitability for any purpose of the Content. Any opinions and views expressed in this publication arethe opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis.The accuracy of the Content should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoevercaused arising directly or indirectly in connection with, in relation to or arising out of the use of theContent.

This article may be used for research, teaching, and private study purposes. Any substantialor systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, ordistribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use canbe found at http://www.tandfonline.com/page/terms-and-conditions

Page 2: EDTA-extractable copper, zinc, and manganese in soils of the Canterbury Plains

New Zealand Journal of Agricultural Research, 1984, Vol. 27: 207-217 207 0028-8233/84/2702-0207$2.50/0 © Crown copyright 1984

EDT A-extractable copper, zinc, and manganese in soils of the Canterbury Plains

R. G. McLAREN R. s. SWIFT Department of Soil Science Lincoln Coilege, Canterbury, New Zealand B. F. QUIN Ministry of Agriculture and Fisheries Private Bag, Wellington, New Zealand

Abstract A large number of topsoil and subsoil samples from the Canterbury Plains were analysed for EDT A-extractable copper, zinc, and man-ganese. The data obtained for all 3 elements were found to be lognormally distributed. Marked differences were apparent in the mean extractable copper and zinc contents of different soil series. Younger soils contained greater amounts of extractable copper and zinc than more strongly developed soils - this trend was not apparent for manganese. Overall correlations between extract-able soil copper and zinc levels, and the concen-trations of these elements in lucerne grown at the sampling sites were poor. However, highly signifi-cant correlations were obtained between the mean extractable copper and zinc levels for individual soil series and the mean copper and zinc concen-trations of lucerne growing on the same series. In general, the levels of extractable copper and zinc in the soils on the Canterbury Plains are very low, and many soils should be regarded as potentially copper and zinc deficient. Manganese levels appear to be adequate. Information on trace element lev-els in soil series could be a useful aid in predicting the probability of trace element deficiencies.

Keywords copper; zinc; manganese; soil fertil-ity; soil series; lucerne; Medicago sativa L.; chelat-ing agents; trace elements; trace element deficiencies; mineral deficiencies; ·nutrient content

Received 31 October 1983; revision 6 January 1984

INTRODUCTION

There is very little information generally available in New Zealand about extractable trace element levels in soils. Tests for trace elements based on soil extraction are not in routine use as an aid for predicting trace element deficiencies. Maps have been compiled showing the levels of the 'total' trace element contents of topsoils in New Zealand (Wells 1962a, b; Wells & Whitton 1979). However, these only indicate broad distribution patterns, and because of local variations they have little signifi-cance at the farm or district level. In addition, cor-relations between total soil trace element levels and trace element availability to plants are not neces-sarily very high. Although Wells (1957) found a sig-nificant correlation between total soil copper (Cu) content and the Cu level in sweet vernal (Anthox-anthum odoratum), the relationship accounted for only a small proportion of the overall variation in plant Cu levels.

In many countries, soil extraction techniques aTe used extensively as a means of assessing soil trace element availability to plants. Such tests are rela-tively easy to perform, and there are many examples in the literature of good correlations between soil test levels and plant trace element levels. Recently in Great Britain there have been attempts to exam-ine the variation in extractable trace element levels within and between soil mapping units (McBratney et al. 1982; Khan & Nortcliff 1982). This type of information could be useful in assessing the like-lihood of trace element problems in specific areas.

In New Zealand, Adams & Elphick (1956) observed differences in available Cu status between different soil series in Canterbury using the Asper-gillus niger method. They also obtained a good cor-relation between available soil Cu status and the Cu content of white clover grown at their sampling sites. In South Canterbury, McLeod & Quin (1979) studied zinc (Zn) deficiency in pasture on Waitohi silt loam soils. They found a relationship existed between extractable soil Zn levels and the Zn con-tent of pasture herbage.

The objective of this study was to examine the variability in extractable trace element levels of 3 trace elements (Cu, Zn, and manganese (Mn» both within and between mapped soil series of the Can-terbury Plains, and to determine ifany relationship

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208

• Methven , • • (0 • .. ~

•••• • • •

• • • • •

• •

• \

.. \ • cJ-" • •• Ashburton

• • • • •• • • • •

,. •

New Zealand J oumal of Agricultural Research, 1984, Vol. 27

.... • OOxford

• •

• • • •

I.

••

•• .... • • •

• • • I. ... -c

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~Culverden •• •

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Fig. 1 Location of sampling sites on the Canterbury Plains.

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Mclaren et al.-Copper, zinc, and manganese in soil 209

existed between soil trace element levels and the trace element content of lucerne (Medicago sativa L.) grown at the sampling sites. The soil samples used in this study were provided by the Ministry of Agriculture and Fisheries, Winchmore, and were taken during a lucerne survey carried out in 1978, the main results of which will be published elsewhere.

MATERIALS AND METHODS

Sampling and analysis Soils Topsoils were sampled using a standard soil corer; 15-20 cores were taken from each paddock and bulked to provide a single composite topsoil sam-ple representing the upper 0-15 cm of soil.

Subsoils were sampled by digging small pits and sampling below 15 cm; 2-3 pits were dug in each paddock and the samples were bulked to provide a single composite sample representing 15-30 cm depth.

Soil-extractable copper, zinc, and, manganese Samples of soil (10 g in duplicate) were extracted for 2 h on an end-over-end shaker with 25 ml 0.04M EDT A (disodium salt of ethylenediaminetetraa-cetic acid, adjusted to pH 6.0 with NaOH). After extraction, the samples were centrifuged and the supernatant solution analysed for Cu, Zn, and Mn by flame atomic absorption spectrophotometry. Results are expressed on the basis of micrograms element extracted per gram of air-dried soil.

Plants At each position in the survey paddocks where a soil Core was taken, 5-6 adjacent lucerne plants were sampled by cutting just above ground level. All the plants from a paddock sampled in this way were combined to provide a single composite sample for that paddock. Most of the lucerne samples were taken at a mature 'hay' stage and only a small pro-portion of samples (less than 15%) were taken at significantly earlier stages of growth. Samples were oven-dried and ground, and analysed for Cu, Zn, and Mn. The results are expressed on the basis of micrograms element present per gram of dried whole plant material.

Location of sampling sites Fig. 1 shows the location of the sampling sites. There is a fairly good spread of sites oyer the main area of the Canterbury Plains and, in addition, sev-eral samples were taken from the Waiau Plains area around Culverden. A total of 182 complete sets of

soil and plant data were used in the statistical analysis described below.

RESULTS AND DISCUSSION

Overall variation in soil-extractable Co, Zn, and Mn levels The data are presented as histograms in Fig. 2 and 3. The distributions of all 3 elements in both top-and subsoil samples were strongly skewed. The coefficients of skewness and kurtosis, calculated as described by Webster (1977), had large positive values emphasising a deviation from the normal distribution (Table I). Transformation of the data to common logarithms substantially reduced the size of this deviation for all sets of data (Table I).

The data were therefore transformed to common logarithms before carrying out the statistical cal-culations. In studies on extractable Cu and cobalt in soil, McBratney et al. (1982) found their data to be lognormally distributed. They noted that this type of distribution is commonly observed in geo-chemistry but that no convincing explanation has so far been presented. In the present study, the spread of values at the lower concentrations is limited by the position of the distributions in rela-tion to the minimum possible value for the ana-lyses, i.e., zero concentration. Although the soils in this study were sampled from a range of soil series, the standard deviations of the data were less than those obtained for extractable Cu, Zn, and Mn in a study of a single soil series by Khan & Nortcliffe (1982). The standard deviation for extractable cop-per was also considerably smaller than that obtained by McBratney et al. (1982) for a range of soil series in south-east Scotland. These observations indicate that the trace element content of the soil parent materials of the Canterbury Plains is relatively uni-form compared to the areas studied by other workers.

The topsoil concentrations of extractable Cu, Zn, and Mn were substantially higher than those in the subsoil (Table I). EDTA is considered to extract primarily elements associated with soil organic matter. Within the surface horizons of soil the con-tinuous growth and decay of plants and cycling of trace elements favours the formation of organo-metallic complexes. Haynes & Swift (1984) also found higher concentrations of EDT A-extractable Cu in soil surface horizons, although total Cu con-centrations were similar to those in the subsoil.

Variation in extractable Cu, Zn, and Mn between soil series Most of the samples used were taken from 8 soil series, and data for other series from which very

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210 New Zealand Journal of Agricultural Research, 1984, Vol. 27

en Q)

c.. E ctS en -0 ... Q) .0 E :J

Z

Untransformed data Log. transformed data

30, Cu 30 Cu

20 20

10 10

0.5 1.0 1.5 2.0 -0.6 0.0

30~ I I I Zn 30

20~ fI~ 20

1O~ AIIIII "" 10

I JlIIIIIIIIIIII}1:6 E:j ~IIIIIIII 0.5

30

15

1.0

30 ).Jg/g

1.5 2.0 -0.6

Mn 30

20

10

45 60

Extractable trace element level

1.0 loglO(jJg/g)

0.0

Mn

2.0

Fig. 2 Distribution of extractable trace element levels in topsoil samples. Normal (transformed data) and lognormal curves (un transformed data) superimposed on histograms are derived from means and standard deviations of log-transformed data.

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Mclaren et al.-Copper, zinc, and manganese in soil

(J) Q) a.. E ctS (J)

"-0 .... Q) .0 E ::::l z

Untransformed data

40 Cu

30

20

10

0.5 1.0 1.5

40~ I I Zn

IfI 1111 1 IlifTI 1Ft 0.5

60

40

20

15

1.0

30 )Jg/g

1.5

Mn

45

Log. transformed data

30 Cu

20

-0.6 0.0

30r Zn

Ftfilllllllllllil I

30

-0.6

1.0 10glO (j.Jg/g)

0.0

Mn

Extractable trace element level

211

2.0

Fig. 3 Distribution of extractable trace element levels in subsoil samples. Normal (transformed data) and lognormal curves (untransformed data) superimposed on histograms are derived from means and standard deviations of log-transformed data.

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212 New Zealand Journal of Agricultural Research, 1984, Vol. 27

Table 1 Statistics of raw and transformed data.

Copper Zinc Manganese

Top- Sub- Top- Sub- Top- Sub-soil soil soil soil soil soil

Raw data Mean (~gfg) 0.76 0.48 0.83 0.49 23.47 10.27 Standard

deviation 0.72 0.49 0.69 0.61 17.95 14.82 Skewness' 4.22 3.66 6.46 9.67 2.34 4.72 Kurtosis' 23.07 18.60 61.31 115.15 7.09 27.55 Data transformed to

log,o Mean (Iog,o ~gfg) -0.22 -0.46 -0.15 -0.41 1.28 0.80 Geometric mean2 (~gfg) 0.60 0.34 0.70 0.39 19.04 6.31 Standard

deviation 0.27 0.33 0.22 0.26 0.28 0.40 Skewness' 0.70 0.39 0.88 0.78 0.18 0.33 Kurtosis' 1.20 0.17 1.63 2.45 -0.05 0.48

'Coefficients for skewness and kurtosis calculated as described by Webster (1977). 2Antilogarithms of mean logarithmic values.

Table 2 Geometric mean values (~gfg) of extractable copper, zinc, and man-ganese contents of soil series.

Copper Zinc Manganese

Top-Soil series Sample size soil

Waimakariri 30 1.08 Templeton 20 0.71 Ruapuna 10 0.54 Chertsey 12 0.50 Glasnevin 9 0.47 Eyre 17 0.45 Lismore 38 0.40 Balmoral II 0.32 Mean 147 0.56

few samples were taken were omitted for this par-ticular comparison, leaving a total of 147 samples. Table 2 shows the mean values for extractable Cu, Zn, and Mn in the different series. Although the ranges of values are quite small for each element analyses of variance indicated that there were sig-nificant between-series differences in all instances except for the subsoil Mn values. The within- and between-series components of variance were cal-culated as described by Webster (1977) and are shown in Table 3.

Nearly half of the total variance of the Cu values could be attributed to between-series variation. However, a comparison of the series means for both topsoil and subsoil Cu using Duncan's multiple

Sub- Top- Sub- Top- Sub-soil soil soil soil soil

0.75 1.14 0.61 17.96 5.27 0.44 0.67 0.39 26.42 9.94 0.32 0.48 0.30 10.76 4.33 0.24 0.55 0.25 24.72 5.83 0.30 0.94 0.56 19.89 7.58 0.21 0.67 0.33 23.35 6.42 0.23 0.52 0.29 15.15 4.63 0.17 0.55 0.31 14.49 4.26 0.32 0.68 0.37 18.50 5.81

range test revealed that only the Waimakariri series was significantly different (P=O.05) from any other series. This series is a recent soil, has the highest extractable Cu level, and is the youngest, least developed soil of the 8 series examined. Adams & Elphick (1956) found a higher level of available Cu in a Waimakariri soil compared to older, more strongly developed soils using the Aspergillus method.

In· the present study the Templeton series was not significantly different from those soil series of lower extractable Cu content yet it had the next highest Cu level to the Waimakariri series. Tem-pleton soils are classified as intergrades between recent and yellow-grey earths. They are more

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Mclaren et al.-Copper, zinc, and manganese in soil 213

Table 3 Components of variation of soil series data.

Total Data variance

Topsoil Cu 0.070 Subsoil Cu 0.113 Topsoil Zn 0.050 Subsoil Zn 0.067 Topsoil Mn 0.090 Subsoil Mn 0.172

strongly developed than Waimakariri soils but less developed than the other 6 soils, which are class-ified as yellow-brown shallow and stony soils asso-ciated with yellow-grey earths or with yellow-grey earth/yellow-brown earth intergrades. The data suggest that extractable Cu levels decrease with an increase in soil development. This could be caused by either leaohing losses or immobilisation of Cu in forms no longer extractable by EDT A. Haynes & Swift (1984) observed decreases of both total Cu content and EDT A-extractable Cu with increased soil development in some loessial soils of New Zealand, and Williams & Mc~ren (1982) have demonstrated that, even within relatively short periods of time, Cu added to soils can become non-extractable with EDT A.

Statistical analysis of the Zn data showed that, although 30-40% of the total variance was caused by between-series variation (Table 3), there were no significant differences (P=0.05) between indi-vidual series means as determined by Duncan's multiple range test. However, with the exception of the Glasnevin series, a similar pattern to that for Cu was shown by the data for Zn (Table 2). The highest extractable Zn level occurred in the Waimakariri series followed by that in the Tem-pleton and Eyre series - the lowest levels were found in the more strongly developed soils. Whit-ton & Wells (1974) found little difference between total Zn content of topsoils of recent, yellow-grey earth, and yellow-brown earth soils; however, they analysed very few samples of recent and yellow-grey earth soils. It is also likely that the determi-nation of extractable Zn levels is a more sensitive technique for detecting differences between soil types than the determination of total Zn values.

In the present study, the extractable Zn value for the Glasnevin series is nearly as high as that for the Waimakariri series - parent material differ-ences might possible account for this. Whereas all the other series are formed predominantly from greywacke, the parent materials for the Glasnevin series include glauconitic limestones and calcar-eous sandstone.

Within-series Between-series variance variance

0.038 (54.3%) 0.032 (45.7%) 0.060 (53.1%) 0.053 (46.9%) 0.030 (60%) 0.020 (40%) 0.048 (71.6%) 0.019 (28.4%) 0.080 (88.9%) 0.010 (11.1%) 0.165 (95.9%) 0.007 (4.1%)

No clear trends were seen in the extractable Mn data (Table 2) - a very small percentage of the total variance could be ascribed to between-series differences (Table 3). The soil chemistry of Mn is more complex than that of Cu or Zn, as Mn is readily affected by changes in redox conditions. As a result, any changes in extractable Mn level with soil development may be less straightforward than the data for Cu and Zn. In addition, there is a prob-lem in attempting to assess soil Mn status in the field on the basis of determinations of extractable soil Mn carried out on air-dried samples of soil in the laboratory.

Variation in Cu, Zn, and Mn levels in lucerne Histograms of the distribution of Cu, Zn, and Mn concentrations in the lucerne samples are shown in Fig. 4. Although all 3 distributions showed some lack of conformity with the normal distribution, the skewness and kurtosis were small compared to the soil distribution data. Transformation of the data to common logarithms did not substantially improve the fit with the normal distribution, as shown by comparing the normal and lognormal distribution curves superimposed on the histo-grams in Fig. 4. Untransformed plant data were therefore used in the statistical calculations.

Table 4 shows the mean trace element concen-trations in the lucerne grown on the 8 main soil series covered in this study. Analyses of variance indicated that there were significant differences (P= 0.05) between-series for Cu and Mn, but not for Zn. However, between- series variation accounted for only 15% of the total variance for Cu, and only 5% for Mn. Comparison of the means by Duncan's multiple range test indicated that there were no sig-nificant differences between means, although the values for Cu did show a similar trend to that observed for the soil Cu data. Cu concentrations. were higher in the lucerne grown on the younger Waimakariri and Templeton soils than in lucerne grown on the older, more strongly developed soils (Table 4).

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214

30

20

10

40

~ 30 a. E <II en '0 ~ 20 Q) .0 E ::::I Z

10

30

20

10

, ......... , I

5

10

25

10

20

,.- ....

50

New Zealand Journal of Agricultural Research, 1984, Vol. 27

15

30 40

75 100

Fig. 4 Distribution of trace ele-ment levels in lucerne samples. -Ilormal distribution - - - lognormal distribution

Nutrient level in lucerne (j.Jg/g)

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McLaren et al.-Copper, zinc, and manganese in soil 215

Table 4 Mean copper, zinc, and manganese concentra- Relationship between soil and plant trace element levels tions (J.lg/g) of lucerne grown on different soil series.

Soil series

Waimakariri Templeton Ruapuna Eyre Lismore Chertsey Glasnevin Balmoral Mean

9

~~8 ~ :::l Q)-() c: .2 .Q

'" ~ 7 .~ C Q) Q) '" () _ c .~ 8 6 c ~ as Q) Q)a. :::Eg-

() 5

Copper

8.03 7.38 7.25 5.59 5.58 5.09 5.07 4.94 6.35

Zinc Manganese

25.37 43.17 22.90 52.05 23.50 50.00 23.50 55.88 22.95 51.66 20.42 60.25 27.11 51.78 24.09 61.27 23.81 52.04

topsoil r~ 0.87** subsoil r~ 0.87**

Copper The lucerne herbage concentrations were signifi-cantly correlated with both topsoil and subsoil Cu levels (Table 5), but the correlations accounted for only 27-28% of the total variation in lucerne Cu levels. Soil pH is known to affect trace element availability to plants, but the incorporation of soil pH data with the soil Cu data in multiple regres-sions did not substantially improve the correlation with lucerne Cu levels.

Correlations between the mean soil Cu levels and mean plant Cu levels for the individual soil series were higher than for the overall data . The differ-ences between either the mean topsoil or subsoil Cu levels of the soil series accounted for just over 70% of the variation in mean lucerne Cu levels between series. The relationships between the mean soil series plant and soil Cu levels are shown in Fig. 5.

The overall mean soil extractable Cu contents of the soils in this survey were 0.60 and 0.34 Itg/g for the topsoil and subsoil respectively (Table 1). Both the mean topsoil and subsoil Cu values are at the low end of the range of values reported in the lit-erature. Most of the soils in this survey would be regarded as Cu deficient for cereal production (Robson & Reuter 1981).

4~1 __ ~ __ ~ ________ ~ __ ~ __ ~ ______ _

The overall low soil Cu levels are reflected in the Cu concentrations found in the lucerne herbage. Fig. 4 shows that a significant proportion of samples have Cu concentrations less than 4 Itg/g, which is the diagnostic critical level for Cu deficiency in lucerne at the hay stage (Ministry of Agriculture and Fisheries 1982). An even greater proportion of samples have Cu concentrations less than 5 Itg/g, the level regarded as the minimum requirement for livestock nutrition (Ministry of Agriculture and Fisheries 1982).

-M -M -M -~ M Mean soil series extractable soil copper level (10910 119/9)

Fig. 5 Relationship between mean soil series lucerne copper concentrations and mean soil series extractable soil copper levels. _. __ topsoil - - _. subsoil

Table 5 Correlations between soil and plant trace element concentrations, using transformed soil data.

Soil parameter

Topsoil Cu Subsoil Cu Topsoil Zn Subsoil Zn Topsoil Mn Subsoil Mn

Linear correlation coefficient with nutrient concentration

in lucerne herbage

r=0.53*** r=O.53*** r=O.26*** r=0.26*** r=0.31*** r=0.18*

% Variation in plant concentrat-ions explained by

correlations

27.2 28.2 6.2 6.4 9.2 2.7

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216 New Zealand Journal of Agricultural Research, 1984, Vol. 27

Zinc Zn concentrations in lucerne were significantly cor-related with soil Zn levels, but the correlations accounted for a negligible proportion of the total variance in herbage Zn levels (Table 5). Multiple regressions in which soil pH data were included with the soil Zn data, gave an improvement on cor-relations with soil Zn alone but still only accounted for up to 15% of the total variance in herbage Zn levels. As with Cu, however, much better correla-tions were obtained between the mean soil Zn and mean plant Zn levels for the individual soil series. The correlation between mean lucerne Zn concen-trations and mean topsoil Zn levels accounted for over 40% of the total variation in the mean lucerne data. Correlation with mean subsoil Zn levels accounted for 70% of the total variation. The rela-tionships between soil series mean plant and soil Zn levels are shown in Fig. 6.

The extractable Zn levels found in this survey are extremely low, with an overall mean topsoil level of 0.70 JlgJg (Table 1). Under conditions of intensive cropping, such levels might be expected to give rise to problems of Zn deficiency. McLeod & Quin (1979) found that an extractable soil Zn level of 0.9 JlgJg (EDT A/ammonium carbonate extractant) was required to prevent Zn deficiency in pasture at high soil pH values. However, the Zn levels found in lucerne (Fig. 4) indicate that this crop is able to cope with the low soil Zn levels. There might though, be some concern at the her-bage Zn levels in relation to livestock nutrition requirements. Ministry of Agriculture and Fisher-ies (1982) quotes requirements of 20 Jlg/g for fat-tening sheep and 30 J,lgJg for milking cows. Most of the survey samples fall below the latter value.

Manganese The correlations between soil and plant Mn levels are summarised in Table 5. Although significant correlations were observed they again accounted for a very small proportion of the total variation in lucerne Mn concentrations. Inclusion of soil pH data with soil Mn data in multiple regressions did improve the correlations with plant Mn levels, but only accounted for up to 25% of the total variation in the plant data. Unlike Cu and Zn, there were no significant correlations between the mean soil and plant levels for the individual soil series.

Overall, the soil Mn levels were much higher than those of Cu or Zn, and, although there is little reli-able information on critical soil Mn levels, it is unlikely that many of the samples in this survey are deficient. Most of the lucerne herbage concen-trations of Mn are above the levels required by either plants or livestock.

28

~ 27

'" '" c~

~ '" ~.3 26 ~ c -;;;2 25 .~ ~

<1> c (/) <1> 24 o g ~ u 23 co u ~.~ 22

21

20 ,

-0.8 -0.6 -0.4 -0.2 0.0 Mean soil series extractable

soil zinc level (I0glO ~g/g)

Fig. 6 Relationship between mean soil series lucerne zinc concentrations and mean soil series extractable soil zinc levels. __ topsoil - - - subsoil

CONCLUSIONS

Of the 3 elements examined in this study, Mn data showed the fewest recognisable trends or signifi-cant correlations between soil and plant Mn levels. No firm conclusions can be drawn for this element, although it is probable that the Mn levels in soil and plant samples were above the minimum requirements for both plant and livestock nutrition.

In contrast, several points arise from consider-ation ofthe Cu and Zn data. The overall ranges of EDT A-extractable Cu and Zn values for the soils of the Canterbury Plains are rather narrow. This may be the result of the relatively uniform nature of the soil parent materials in this area. However, for extractable Cu and perhaps to a lesser extent for extractable Zn, there are significant differences between the mean values obtained for individual soil series. The highest values were recorded for a younger, more recent soil, and values were consid-erably lower in older soils showing a greater degree of development.

Positive correlations occur between the average extractable Cu or Zn contents for a soil series and the average concentration of these elements found in lucerne grown on the same series. Thus, infor-mation on extractable Cu and Zn levels for par-ticular soil series could be used to predict the probability of deficiencies of these elements for crops grown on the series. However, with lucerne, it seems unlikely (on the basis of the overall cor-relations between plant and soil data) that soil extractable Cu and Zn values have much value in

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McLaren et al.-Copper, zinc, and manganese in soil 217

predicting plant nutrient concentrations at indivi-dual sites. This is true for both topsoil and subsoil levels. Although subsoil Cu and Zn levels are much lower than topsoil levels, the 2 sets of values are highly correlated. Subsoil data does not appear to be any more reliable than topsoil data as an indi-cator of nutrient status for deep rooting crops like lucerne. As well as soil content of Cu and Zn there are obviously many other factors such as soil mois-ture status, soil pH and major nutrient levels which can affect the Cu and Zn content of plants.

The levels of extractable Cu and Zn in the soils of the Canterbury Plains, when compared to soils elsewhere, are extremely low. Some of the soil series examined in this study appear potentially deficient in Cu and Zn if they are to be used intensively. Further intensification of crop production in parts of the Canterbury Plains following more efficient use of irrigation or the introduction of horticultural crops, is a distinct possibility. Horticultural crops in particular are known to be very susceptible to various trace element deficiencies. A firm knowl-edge of the distribution of trace elements in the soils of the Canterbury Plains, and identification of the soil types most likely to cause deficiencies is therefore highly desirable.

ACKNOWLEDGMENTS We thank Mr R. C. Stephen of the MAFfor further infor-mation regarding the lucerne survey, and Mr P. Carey for analysing the soils.

REFERENCES Adams, A. F. R.; Elphick, B. L. 1956: The copper content

of some soils and pasture species in Canterbury. New Zealand journal of science and technology A38: 345-358.

Haynes, R. J.; Swift, R. S. 1984: Amounts and forms of micronutrient cations in some loessial grassland soils of New Zealand. Geoderma, (in press).

Khan, M. A.; Nortc1iff, S. 1982: Variability of selected soil micronutrients in a single soil series in Berk-shire, England. Journal of soil science 33: 763-770.

McBratney, A. B.; Webster, R.; McLaren, R. G.; Speirs, R. B. 1982: Regional variation of extractable cop-per and cobalt in the topsoil of south-east Scot-land. Agronomie 2: 969-983.

Mcleod, C. c.; Quin, B. F. 1979: Pasture responses to zinc on Waitohi silt loam. New Zealand journal of experimental agriculture 7: 135-139.

Ministry of Agriculture and Fisheries. 1982: Fertiliser and lime recommendations for pastures and crops in New Zealand. Ministry of Agriculture and Fish-eries, Wellington.

Robson, A. D.; Reuter, D. J. 1981: Diagnosis of copper deficiency and toxicity. In: Loneragan, J. F.; Rob-son, A. D.; Graham, R. D. ed .. Copper in soils and plants. Sydney, Academic Press, pp. 287-312.

Webster, R. 1977: Quantitative and numerical methods in soil classification and survey. Oxford, Claren-don Press.

Wells, N. 1957: Soil studies using sweet vernal to assess element availability. Part 3. Copper in New Zealand soil sequences. New Zealand journal of science and technology B38: 884-902.

---- I 962a: Total copper in topsoils. Soil Bureau Single factor maps 41 and 42.

I 962b: Total manganese in topsoils. Soil Bureau single factor maps 65 and 66.

Wells, N.; Whitton, J. S. 1979: Total zinc in topsoils. Soil Bureau single factor maps 39 and 40.

Whitton, J. S. and Wells, N. 1974. A pedochemical sur-vey 2. Zinc. New Zealand journal of science 17: 350-367.

Williams, J. G.; McLaren, R. G. 1982: Effects of dry and moist incubation of soils on the extractability of native and applied soil copper. Plant and soil 64: 215-244.

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