BUREAU OF SUGAR EXPERIMENT STATIONS , AUSTRALIA

FINAL REPORT SRDC PROJECT BS67S

EXTENT OF ZINC DEFICIENCY IN CANE GROWING SOILS OF by J R Reghenzani SD93001

Principal Investigator: Mr J R Reghenzani Research Officer BSES PO Box 566 TULLY Q 4854

Phone: (070) 68 1488

This project was funded by the Sugar Research and Development Corporation during the 1991-92 financial year.

BSES Publication SRDC Final Report SD93001 June 1993 CONTENTS Page No

1. SUMMARY 1

2. BACKGROUND 1

3. PROJECT OBJECTIVES 2

4. INTRODUCTION 2

5. METHODOLOGY 2

5.1 Survey of the extent of zinc deficiency 2 5.2 Field trials 3

6. RESULTS AND DISCUSSION 3

6.1 Survey of extent of zinc deficiency 3

6.1.1 Soil sampling practices 3 6.1.2 Extractable zinc according to soil association 4 6.1.3 Extractable zinc according to soil type 4 6.1.4 Estimation of areas at risk from zinc deficiency 6 6.1.5 Mapping of low zinc sites 9 6.1.6 General nutritional status of farmer's soil samples collected in 1991 9

6.2 Field trials 15

6.2.1 Influence of zinc treatment on whole plant zinc concentration 15 6.2.2 Influence of zinc treatment on total zinc uptake 16 6.2.3 Influence of lime on zinc uptake and concentration 16 6.2.4 Influence of zinc on uptake and concentration of other elements 17 6.2.5 Recommendations for zinc treatment 17

7. DIFFICULTIES 17

8. RECOMMENDATIONS FOR FUTURE RESEARCH 18

9. PUBLICATIONS 18

10. REFERENCES 18 1. SUMMARY

Collation and interpretation of soil analysis data has shown a strong relationship between soil type and extractable zinc. Extractable zinc in soils followed the order: metamorphic, beach ridge and granite soils < organic and alluvial soils < basaltic soils. More than 15% (18 000 ha) of north Queensland sugarcane soils from Mossman to Ingham were estimated to be at risk from zinc deficiency and associated constrained productivity. This study has identified and mapped low zinc soils and remedial action can now be taken. While alternative zinc forms applied with planting fertiliser have a role, preliminary data from this project does not support a change in the recommended application technique of zinc sulfate heptahydrate, broadcast and incorporated before planting.

2. BACKGROUND

Responses in cane and sugar yield were demonstrated to zinc applied to a deficient soil in the Mulgrave Mill area as part of project BS14S (Reghenzani, 1990). Analysis of soils in the Hambledon, Mulgrave and Babinda mill areas showed deficient levels of extractable zinc and it was estimated that approximately 30% of the area surveyed was below the critical level.

A relationship was observed between soil type and zinc deficiency symptoms identified from the Herbert Valley north. Darker coloured, light textured soils, particularly those derived from granite appeared prone to zinc deficiency.

Reghenzani (1990) noted that:

1. Some cane varieties do not exhibit leaf deficiency symptoms, even when yield is depressed, but will respond to applied zinc, hence the need to develop a suitable soil test.

2. A soil test using a hydrochloric acid extract was more sensitive in identifying deficient soils than the current DTPA extract, hence the recommendation to change to the new extract and to promote the test to commercial firms.

3. Application of lime increased severity of zinc deficiency. As large areas of north Queensland sugarcane were deficient in calcium, zinc deficiency would become more of a problem as fields were limed.

These results suggested that low levels of soil zinc in the northern region may be limiting yield and could be associated with the yield decline problem.

Laboratories servicing the sugar industry introduced the hydrochloric acid test for zinc in 1991 and various forms of zinc fertiliser became available for use by farmers.

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3. PROJECT OBJECTIVES

 Identify and delineate the soil types on which a response to applied zinc may occur.

 Identify the most appropriate zinc application technique.

NB These objectives were limited since the project was of one-year duration.

4. INTRODUCTION

The extent of zinc deficiency as a newly discovered nutritional problem of sugarcane was not well defined. The introduction of the hydrochloric acid zinc test by analytical laboratories, following promotion by BSES, permitted evaluation of zinc deficiency and its relationship with soil type, before widespread application of zinc fertilisers.

This approach allowed estimation of the extent of the problem by combining the data collected for this project with recently completed soil maps, achieving the first project objective. Further valuable data was gained on the overall nutritional status of northern soils and this has been used in extension services to farmers.

Several alternative techniques have become available to growers to treat zinc deficiency. These have been evaluated in three field trials established in far north Queensland achieving the final project objective.

5. METHODOLOGY

5.1 Survey of the extent of zinc deficiency

Soil analysis data from Mossman to Ingham were collated from the two laboratories (Incitec, and Mossman Central Mill Pty Ltd) which service the majority of commercial analysis requests in the region and from samples analysed by the Bureau of Sugar Experiment Stations (BSES) as part of research programs. No conversions were necessary for the newly adopted 0.1M hydrochloric acid extract for zinc, as Incitec and Mossman have adopted the BSES method for this assay.

Data were collated in a `Paradox' database. In addition to analytical data, where available, the following information was recorded: laboratory name, date and sample number, farmer's name and initials, block number, district, mill, soil texture, map unit soil association, and Australian Map Grid (AMG) coordinates.

The soil classification system adopted was that published by Murtha (1986, 1989), Wilson and Baker (1990), Cannon et al. (1992) and Murtha et al. (1993), which collectively cover all cane growing soils in the study area. Where fields comprised a mixture of soil associations, the dominant association was used for subsequent interpretation.

Critical values used to categorise the data reported by Reghenzani (1990) for zinc have been listed in Table I. The geographic information system (GIS) package `MapInfo' was used to 3 present locational data (Figs 1-4).

Table I Zinc status of north Queensland soils as determined from farmers' samples taken in 1991 for all northern mill areas

Category Levels (mg/kg) Percentage of samples Very low 0.2 or less 2 Deficient >0.2 to 0.6 13 Adequate over 0.6 85

Mean value  c.i.(a) 1.91  0.15

(a) c.i. = 95% confidence interval.

As well as classifying soils into map unit soil associations, they were grouped into categories of similar type. This data were used in conjunction with data on distribution of soil types provided by C D Smith (Pers comm 1988), to estimate the area of soils in the study area which had less than the critical level of zinc.

5.2 Field trials

Three field trials were established to identify the most appropriate zinc application technique. The trials were established in Mulgrave, South Johnstone and Victoria mill areas. All trials evaluated three zinc application techniques; zinc sulfate heptahydrate sprayed onto the soil surface and incorporated by cultivation before planting, zinc sulfate monohydrate blended with planting fertilisers, and zinc oxide coated fertiliser prills.

Two of the trials used randomised complete block factorial designs to investigate zinc form and rate while the third used a randomised strip trial design to investigate zinc application technique. The effect of lime rate on zinc uptake was studied at two sites. Whole top samples were collected from the plant crop towards the end of 1991. Data on dry weight yield, zinc concentration and zinc uptake were obtained for each plot.

6. RESULTS AND DISCUSSION

6.1 Survey of extent of zinc deficiency

6.1.1 Soil sampling practices

Data on soil sampling practices are summarised in Table II and indicate a wide range in sampling intensity throughout the northern mill regions. Mossman area was sampled most intensively, with 62% of assignments sampled in 1991. There is room for improvement in all other mill areas, where an average of only one assignment holder in four took soil samples for analysis. This sampling rate is poor, but is better than the 11% rate reported by Sedl (1967) for cane farmers on a State-wide basis. Those who did sample took about two 4 samples per assignment, except in Mossman, which had about twice this sampling intensity. Soil sampling and analysis has been strongly encouraged in the Mossman area and costs are subsidised.

Samples were taken mainly at the beginning of a crop cycle, so the area planted per sample was calculated. Table II shows a tenfold range in this value with Mossman at 5.3 ha per sample, and Mourilyan at 52.9 ha per sample. The average intensity of 19.4 ha per sample was similar to 20.6 ha per sample calculated from data reported by Sedl (1967), allowing for 80% rotation practiced at that time.

Zinc assays were requested on over 89% of soils tested in north Queensland in addition to routine assays for other nutrients. This was a very satisfactory adoption of the HCl soil test, which following BSES research, became available through Incitec and Mossman Mill.

6.1.2 Extractable zinc according to soil association

Of the 1436 soil analysis gathered, 1285 were analysed for extractable zinc, using the 0.1 M hydrochloric acid extract. These soils were classified as belonging to 70 of the 104 map unit soils associations in the study area. Soil associations with more than 10% of samples below the critical zinc value, and with more than 10 samples assayed, are listed in Table III in decreasing order of suspected zinc deficiency problems. Data on remaining soil associations have been summarised in Tables IV and V. Table IV lists 24 associations which had less than 10% of samples below the critical level, or had ten or fewer samples assayed. Table V lists 26 associations which did not have any samples below the critical level.

Risk of zinc deficiency was highest for soil associations listed towards the head of Tables III and IV. Overall risk varies directly with percentage figures in the right column and inversely with mean HCl zinc value. Greater reliance should be placed on data with a low confidence interval and for those soil associations with greater numbers of assays.

6.1.3 Extractable zinc according to soil type

Grouping of soils according to soil type allowed recognition of three risk groups for potential zinc deficiency (Table VI). Soils formed on metamorphic rock, beach ridges and granite had the lowest levels of HCl extractable zinc and the highest percentage of soils below the critical limit. A second grouping of organic and tidal zone soils and those formed on well drained and poorly drained alluvium had higher extractable zinc and a lower but still important percentage of soils below the critical limit. The final classification of basaltic soils showed the highest level of extractable zinc and the lowest percentage of samples below the critical limit.

These data are consistent with findings for South African sugarcane soils, where zinc content of coarse sandy soils was low (Maud, 1958) and the highest incidence of zinc deficiency occurred on soils derived from granite (Anon, 1977). 5

Table II Soil sampling practices in far north Queensland in 1991

Mill Area planted in No. of farmers' % of Assignments Average samples per Total area of plant per

1991 (ha)(b) soil samples sampled(c) assignment(d) sample(e) Mossman 2027 381 62.0 3.8 5.3 Mulgrave (a) 3000 107 17.6 2.1 28.0 Babinda 2520 96 17.5 1.9 26.2 Mourilyan 2010 38 9.1 1.8 52.9 S. Johnstone 2617 174 27.6 2.6 15.0 Tully 3258 96 25.6 1.8 33.9 Macknade 3000 89 22.3 1.9 33.7 Victoria 6261 294 31.3 2.1 21.3 Combined 24693 1275 25.2 2.4 19.4

(a) Includes Hambledon (b) Includes plant and replant area (c) In general it was not possible to identify (d) Average number of soil samples per assignment sampled separate farms under the one name, so these (e) Total area planted in mill area per soil sample taken groups were regarded as a single assignment.

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Table III Soil associations with more than ten % of samples below the zinc critical value according to the HCl extract and where greater than ten samples were collected until the end of 1991

Map unit Soil Number of Mean HCl % of samples with association samples zinc  c.i. the critical level or (mg/kg) (a) less (b) Lu Lugger 11 0.89  0.56 54.55 Ms Mission 86 0.88  0.17 40.70 Hu Hull 13 0.72  0.27 38.46 Po Ponzo 21 0.88  0.38 33.33 He Hewitt 14 2.09  1.70 28.57 Jr Jarra 15 1.41  0.67 26.67 Co Coom 50 1.17  0.23 26.00 Ga Galmara 24 0.99  0.38 25.00 Cl Clifton 42 1.28  0.31 23.81 Mb Malbon 17 1.41  0.55 23.53 Dt Daintree 10 1.30  0.71 20.00 Mn Mossman 97 1.10  0.14 19.59 Tu Tully 118 1.42  0.20 16.10 Th Thorpe 45 1.59  0.77 15.56 Bg Bulgun 36 1.31  0.42 13.89 Li Liverpool 61 1.57  0.23 11.48 Pg Pin gin 53 1.68  0.38 11.32 Tb Toobanna 55 10.91 2.86  1.30 As Ashton 20 10.00 1.00  0.28 Mn Manor 10 10.00 2.31  2.11

(a) c.i. = 95% confidence interval, M = Missing due to sample size. (b) Soil associations with 10% or more of samples with the critical level (0.6 mg Zn/kg) or less.

6.1.4 Estimation of areas at risk from zinc deficiency

The percentage of samples with less than the critical level of zinc within soil type groups (Table VI) were combined with data provided by C D Smith (Pers comm 1988) on the percentage of soil type groups in each mill area, to calculate the area potentially at risk from zinc deficiency (Table VII).

The greatest percentage of soils at risk of zinc deficiency was in the most northern mill areas, and generally, the risk declined to the south. This finding reinforced observations made since the discovery of zinc deficiency. Alluvial soils had a low percentage of `at risk' soils (Table VI), but on an area basis they constituted 57% of low zinc soils (Table VII), because of their extensive distribution in the study area.

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Table IV Soil associations with less than ten % of samples below the zinc critical value, according to the HCl extract, or where fewer than 10 samples were collected until the end of 1991

Map Soil Number of Mean HCl % of samples with unit association samples zinc  c.i. (mg/kg) the critical level or (b) (a) less Gg Googarra 2 0.44  M 100.00 Km Kirrama 1 0.46  M 100.00 Am Alma 1 0.50  M 100.00 An Arnot 1 0.52  M 100.00 Pr Prior 5 0.69  0.37 60.00 Cn Canoe 2 1.18  M 50.00 Bu Bulguru 5 1.49  1.43 40.00 Ku Kurrimine 3 0.69  0.79 33.33 Al Althaus 3 1.11  1.54 33.33 Ru Rumula 3 2.51  5.87 33.33 Ty Tyson 4 0.72  0.45 25.00 Bi Bicton 8 1.46  1.40 25.00 Ma Maria 5 0.93  0.63 20.00 Il Inlet 6 1.07  0.46 16.67 Ho Holloway 8 1.25  0.59 12.50 Bw Bluewater 8 4.12  4.93 12.50 Br Brosnan 11 1.73  0.56 9.09 Pl Palm 13 2.36 7.69  1.12 Nl Newell 28 1.16 7.14  0.19 Yr Yuruga 15 1.86 6.67  1.31 Ag Abergowrie 19 2.55 5.26  2.07 Vi Virgil 42 2.06 4.76  1.31 Ih Ingham 24 2.35 4.17 0.69 Eu Eubanangee 27 2.72  3.70  1.88

(a) c.i. = 95% confidence interval, M = Missing due to sample size. (b) Soil associations with ten percent or more of samples with the critical level (0.6 mg Zn/kg) or less 9

Table V Soil associations with no samples below the critical value according to the HCl extract

Map unit Soil association Number of Mean HCl zinc  c.i. samples (mg/kg)(a) Sl Sumalee 2 0.77  M Ki Kimberley 2 1.00  M Lc Lucy 1 1.05  M Ba Banyan 1 1.30  M Mu Mundoo 5 1.55  0.77 Ra Ramleh 7 1.57  0.43 Ti Timara 10 1.62  0.49 Rp Ripple 3 1.64  1.08 Tk Tinkle 1 1.92  M In Innisfail 17 1.95  0.59 Ml Molonga 6 2.22  M Br Brae 1 2.58  0.47 Hl Hamleigh 39 2.67  2.93 Bb Byabra 6 2.75  1.87 So Somerset 3 3.43  1.74 Mn Midway 9 3.56  2.68 Ch Catherina 3 3.64  2.44 Lh Leach 13 3.68  1.64 Tr 19 3.69  1.20 Hb Herbert 24 3.74  1.50 Mk Macknade 13 4.07  M Hv Hillview 1 4.99  M Gu Garradunga 2 7.12 M Ln Lannercost 5 7.38  Et Edmonton 2 10.19  11.12 Mb Podzol 1 20.00  M  M

(a) c.i. = 95% confidence interval, M = Missing due to sample size. (b) Soil associations with 10% or more of samples with the critical level (0.6 mg Zn/kg) or less.unit soil associations. An additional 34 minor map unit soil associations were not represented by samples taken during the survey period.

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Table VI Levels of HCl extractable zinc and % of samples with less than the critical level for soils grouped according to soil type

Soil type Number of Mean HCl zinc % of samples with samples  c.i. the critical level or (mg/kg) (a) less Metamorphic 162 1.14  0.21 32.72 Beach Ridges 44 1.11  0.24 27.27 Granite 88 1.59  0.59 27.27 Organic & tidal zone 14 2.01  1.16 14.29 Well drained alluvial 503 1.86  0.18 12.33 Poorly drained alluvial 340 2.04  0.29 11.47 Basaltic 90 2.10  0.63 7.78 Unidentified 44 3.75  1.79 13.64 Combined 1285 1.86  0.14 15.95

(a) c.i. = 95% confidence interval.

As expected, the metamorphics, granites and beach ridge soils each constitute large areas at risk from zinc deficiency.

Samples assayed for zinc were regarded as representative of the region, due to similar combined percentage figures in Tables VI (16%) and VII (15%). Over 18 000 ha was estimated to be potentially at risk from zinc deficiency in the far northern region. This exceeds 15% of the total canegrowing area, sufficient to influence the productive potential of the northern zone.

6.1.5 Mapping of low zinc sites

AMG coordinates were assigned to each soil sample. This procedure permitted the utilisation of GIS technology. Figures 1 to 4 display the distribution of sites which had less than the critical zinc concentration. There was a clustering in the most northern mill areas, frequently at sites close to mountain ranges. Other localities with low zinc were the Atherton Tableland, Mena Creek, Japoonvale to Kurrimine Beach, the Syndicate, Stone River and the Kandeer section of Abergowrie.

6.1.6 General nutritional status of farmer's soil samples collected in 1991

Data collected from farmers' sites in 1991 indicated that the majority of soils had high levels of phosphorus and moderate levels of potassium. On the other hand, marginal or deficient levels of calcium, magnesium and sulfur were shown in 63%, 45% and 22% of samples respectively. The data indicated that deficiency of calcium, magnesium and to a lesser extent sulfur had potential to severely limit yield in the northern region, unless treated. 11

Table VII Potential areas at risk from zinc deficiency for far Northern Mills

Estimated area with less than the critical zinc limit (ha) % of Mill area

Soil type (a)

Mill 1992 area (ha) 1 2 3 4 5 6 Total Mossman 8993 319 0 883 0 477 144 1823 20.3 Mulgrave(b) 14850 40 23 1603 769 586 221 3244 21.8 Babinda 11549 31 144 227 787 285 424 1898 16.4 Mourilyan 12841 560 200 420 0 491 339 2010 15.7 South Johnstone 11974 33 289 431 65 443 343 1604 13.4 Tully 14920 0 0 195 610 446 599 2251 15.1 Macknade 15104 82 0 0 165 652 1022 1921 12.7 Victoria 30448 0 0 0 83 1314 2235 3632 11.9 Combined 120679 1066 655 3759 2480 5093 5328 18382 15.2

(a) Soil type: 1. Beach ridge soils 2. Basalt soils 3. Metamorphic soils 4. Granite soils 5. Well drained alluvium 6. Poorly drained alluvium (b) Includes Hambledon

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There must be some uncertainty in applying the above findings to the whole region as the nutritional status of the 75% of assignment holders who did not sample was unknown, some samples may have been taken to diagnose problems of poor areas, and samples taken from older ratoons may not be representative of younger, treated ratoons. The findings were still cause for concern, particularly considering the extension program targeted at improving the nutritional status of northern soils, following findings of significant yield responses to calcium and magnesium by Ridge et al. (1980).

Grower reluctance to overcome calcium and magnesium deficiency may be due to the high initial cost of treatment, estimated at over $500/ha when applied as Blend 3 at 5t/ha in north Queensland. The cost of $60/ha to apply zinc is likely to result in more rapid treatment of this deficiency. Growers have generally maintained application of the major elements N, P and K, sometimes at levels beyond BSES recommendations. However excess application of these elements will not compensate for deficiency of Ca, Mg, Zn or S.

The time is opportune for growers to review their fertiliser program, and subject to economic circumstances, use the savings to treat deficiencies in calcium, magnesium, sulfur and zinc. The soil data indicated that moderate to high soil levels of phosphorus and potassium would justify lower application rates of these elements.

6.2 Field trials

6.2.1 Influence of zinc treatment on whole plant zinc concentration

The influence of zinc rate on zinc concentration in whole tops was investigated at two of the three sites. There was a highly significant increase in zinc concentration with increasing zinc rate (Table VIII).

Table VIII Effect of zinc rate on zinc concentration in whole tops

Zinc rate (kg/ha Zinc concentration mg Zn/kg d.w. whole tops Arcidiacono Leonelli 0 13.9 11.6 5 15.5 15.5 10 16.4 18.3 lsd 5% 0.9 1.2 1% 1.2 1.7

There was no significant effect of zinc form on zinc concentration except at Berryman's site, where zinc monohydrate at 10 kg Zn/ha resulted in higher zinc concentrations than zinc oxide and zinc heptahydrate forms in the early stages of growth. All zinc forms increased 18 concentration of zinc in whole tops over the control treatment (Table IX). There were no detectable differences between the effect of zinc source on concentration at the two remaining sites.

Table IX Effect of zinc form on zinc concentration in whole tops at Berryman's site

Zinc form mg Zn/kg d.w. whole tops Monohydrate 21.2 Oxide 15.0 Heptahydrate 14.3 Control 10.3 lsd 5% 2.1 1% 3.2

6.2.2 Influence of zinc treatment on total zinc uptake

There was a significant effect of zinc form on zinc uptake in whole cane tops at Berryman's and Leonelli's sites (Table X). Monohydrate zinc resulted in superior zinc uptake at Berryman's, while heptahydrate zinc resulted in superior uptake at Leonelli's site.

Table X Effect of zinc form on total zinc uptake (g/ha)

Zinc form Zinc uptake whole cane tops (g Zn/ha) Arcidiacono Berryman Leonelli Heptahydrate 58.0(16) 14.3 (3) 22.6 (14) Oxide 54.9(16) 15.0 (3) 17.5 (14) Monohydrate 49.0(16) 21.2 (3) 17.4 (14) Control 50.2(24) 10.3 (3) 14.5 (21) lsd 5% NS 2.1 3.2 (14/14) 3.0 (14/21) 1% NS 3.2 4.3 (14/14) 3.9 (14/21)

NB Numbers in brackets show the degree of replication NS = not significant 19

6.2.3 Influence of lime on zinc uptake and concentration

The influence of lime at 2.5 and 5 t/ha on zinc uptake and concentration was investigated at two sites. At Leonelli's site there was no influence of lime rate on zinc uptake from control plots. In addition, at Arcidiacono's site, lime rate had no influence on zinc uptake from plots treated with either of the three zinc forms at 10 kg zinc per hectare.

While these trials showed no effect of lime application on zinc uptake, it has been shown elsewhere (Reghenzani, 1990) that liming can induce zinc deficiency.

6.2.4 Influence of zinc on uptake and concentration of other elements

Application of zinc increased magnesium concentration in whole tops at Arcidiacono's site. Application as heptahydrate rather than monohydrate or oxide resulted in increased magnesium concentration in tops at Berryman's site and increased magnesium uptake at Leonelli's site.

Zinc applied as heptahydrate rather than monohydrate or oxide increased both calcium and copper uptake at Leonelli's site.

6.2.5 Recommendations for zinc treatment

Early data presented in this report indicate that either heptahydrate zinc broadcast prior to planting or monohydrate zinc applied during planting have resulted in the superior zinc uptake. It however is difficult to extrapolate this result to uptake for the entire crop or to infer a yield advantage at harvest. At the December sampling, the crop had taken up only 3 to 10% of total requirements.

In the case of heptahydrate zinc, there were other benefits including improved magnesium, calcium and copper status which support the case for continued recommendation as the preferred zinc application technique although the other zinc fertiliser forms are also of value.

7. DIFFICULTIES

Identification of soil sampling sites took considerable time. Frequently this was due to inadequate labelling of the results sheets. Standard procedures in this respect and training in soil identification would benefit the industry.

Because SRDC funding was for one-year only, constraints of time and scope on this research allowed only preliminary results to be obtained on the effectiveness of zinc treatment techniques. 20

8. RECOMMENDATIONS FOR FUTURE RESEARCH

The zinc survey has demonstrated the value of collation and interpretation of the large amount of soil analytical data generated by the sugar industry each year. It is recommended that a GIS-based database be established to collate this information on an industry wide basis, so that regular reports may be produced to assist in the identification of production problems due to nutritional imbalances, deficiencies and toxicities.

The trial sites established as part of this project will be followed through to harvest of the plant and ratoon crops. Analysis of plant and ratoon data will provide a definitive answer about suitable zinc treatment techniques.

There is a need to investigate reasons for limited use of soil sampling, and to develop extension techniques to overcome this problem and the problems of nutritional constraints which this study has shown has capacity to reduce productivity.

9. PUBLICATIONS

Reghenzani, J R (1993). A survey of the nutritional status of north Queensland sugarcane soils with particular reference to zinc. Proc. Aust. Soc. Sugar Cane Technol. 1993 Conf. pp 298-304.

Reghenzani, J R (1993). Plan your fertiliser program. Aust. Canegrower. 15(7):26.

10. REFERENCES

Anon (1977). Frequency of zinc deficiency. Ann. Rep. Exp. Stn. S. Afr. Sugar Assoc., 1977, p35.

Cannon, M G, Smith, C D and Murtha, G G (1992). Soils of the Cardwell-Tully area, north Queensland. CSIRO Aust. Div. Soils, Divl. Rep. No. 115.

Maud, R R (1958). Plant nutrient derivation from soil minerals. Proc. S. Afr. Sugar Technol. Assoc. 32: 112-119.

Murtha, G G (1986). Soils of the Tully-Innisfail area, north Queensland. CSIRO Aust. Div. Soils, Divl Rep. No. 82.

Murtha, G G (1989). Soils of the Mossman-Cape Tribulation area, north Queensland. CSIRO Aust. Div. Soils, Divl Rep. No. 102.

Murtha, G G, Smith, C D and Cannon, M G (1993). Soils of the Babinda-Cairns area, north Queensland. CSIRO Aust. Divl Soils, Divl. Rep. (in preparation).

Reghenzani, J R (1990). The effect of zinc deficiency as a factor limiting sugarcane growth. Final Report to Sugar Research Council, Project BS14S. BSES, Brisbane. 21

Ridge, D R, Hurney, A P and Haysom, M B C (1980). Some aspects of calcium and magnesium nutrition in north Queensland. Proc. Aust. Soc. Sugar Cane Technol. 1980 Conf. pp55-60.

Sedl, J M (1967). The operation of a soil testing and advisory system. Proc. Qd. Soc. Sugar Cane Technol., 34, 95-100.

Wilson, P R and Baker, D E (1990). Soils and agricultural land suitability of the wet tropical coast of north Queensland: Ingham area. Qd. Dept Prim. Ind. Land Res. Bull. QV90001.