Identification and Management of Soil Acidity in Irrigated Farming Systems of Southern NSW

Identification and Management of Soil Acidity in Irrigated farming systems of Southern NSW

A report for the Rural Industries Research and Development Corporation

By HG Beecher BA Lake NSW Agriculture

August 2004

RIRDC Publication No 04/007 RIRDC Project No DAN-161A

ISBN 0 642 587175 ISSN 1440-6845

Identification and Management of Soil Acidity in irrigated lands of Southern NSW Publication No. 04/007 Project No. DAN 161A.

The views expressed and the conclusions reached in this publication are those of the author and not necessarily those of persons consulted. RIRDC shall not be responsible in any way whatsoever to any person who relies in whole or in part on the contents of this report.

This publication is copyright. However, RIRDC encourages wide dissemination of its research, providing the Corporation is clearly acknowledged. For any other enquiries concerning reproduction, contact the Publications Manager on phone 02 6272 3186.

Researcher Contact Details H.G. Beecher NSW Agriculture NSW Agriculture Yanco Agricultural Institute YANCO NSW 2703 Phone: 02 69512725 Email: [email protected]

B. A. Lake NSW Agriculture Yanco Agricultural Institute YANCO NSW ) 2703 Phone: 02 69512629 Email: [email protected]

RIRDC Contact Details Rural Industries Research and Development Corporation Level 1, AMA House 42 Macquarie Street BARTON ACT 2600 PO Box 4776 KINGSTON ACT 2604

Phone: 02 6272 4819 Fax: 02 6272 5877 Email: [email protected]. Website: http://www.rirdc.gov.au

Published in August 2004 Printed on environmentally friendly paper by Canprint

Foreword

Soil acidification under current agricultural practices is an important land degradation process. Increasing soil acidity causes reduced yield, leading to reduced water and land use efficiency and a reduced range of crop species that can successfully be grown within the irrigated cropping system. Irrigated cropping industries of the Murrumbidgee and Murray Valleys in southern NSW are primarily rice based farming systems. Whilst rice under flooded conditions is relatively unaffected by soil pH, crops potentially grown in rotation with rice may be significantly affected by low soil pH.

This publication reports investigations into changes in surface soil acidity over time and the extent and severity of topsoil and subsoil acidity in irrigated lands of southern NSW.

This project was funded from industry revenue which is matched by funds provided by the Australian Government.

This report, a new addition to RIRDC’s diverse range of over 1000 research publications, forms part of our Rice R&D program, which aims to improve the profitability and sustainability of the Australian rice industry.

Most of our publications are available for viewing, downloading or purchasing online through our website:

• downloads at www.rirdc.gov.au/fullreports/index.html • purchases at www.rirdc.gov.au/eshop

Simon Hearn Managing Director Rural Industries Research and Development Corporation

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Acknowledgments

This work was undertaken in a project primarily funded by NSW Acid Soil Action with supplementary funding from RIRDC. The co-operation of a very large number of irrigators particularly rice growers in Southern NSW in allowing access to their properties for sampling is gratefully acknowledged. Loan of soil sampling equipment from NSW Agriculture staff at Deniliquin is also acknowledged. Pivot Fertilisers are acknowledged for providing access to soil test data and for undertaking soil analysis at a reduced cost. Incitec Fertiliser is acknowledged for making soil test data available.

Contents

Foreword...... iii Acknowledgments...... iv Executive Summary ...... vi

1. Introduction ...... 1 1.1 Background ...... 1 1.2 Subsoil acidity...... 1 1.3 Acidification processes...... 2

2. Objectives of the project ...... 3

3. Methodology ...... 3 3.1 Soil Mapping...... 3 3.2 Collation of existing soil test results ...... 3 3.2.1 Conversion of pH (water) to pH (CaCl2) ...... 4 3.3 Soil sampling program ...... 4 3.3.1 Soil sampling...... 4 3.3.2 Soil sample preparation and analysis methods...... 4 3.3.3 Cropping system effects ...... 4 3.4 Soil pH mapping...... 5

4. Detailed Results ...... 6 4.1 Historical results:...... 6 4.2 Temporal Aspects...... 8 4.3 Comparison of Pre-1985 and Post 1995 soil pH values for irrigation Districts...... 8 4.4 Spatial Aspects ...... 10 4.4.1 Postcodal based Soil pHs ...... 10 4.6 Sub-soil pH Levels ...... 17 4.7 Cropping system effects ...... 21 4.8 Soil type/ soil texture effects...... 23 4.9 Exchangeable Aluminium Levels...... 25

5. Discussion of Results ...... 27 5.1 Project achievement ...... 27 5.2 Implications...... 27

6. Recommendations ...... 28 6.1 Communication strategy...... 28

7. References ...... 30

8. Publications arising from this Project ...... 32

9. Communications/ Extension...... 33

Executive Summary

Soil acidification under current agricultural practices is an important land degradation process. In New South Wales, 13.7 M ha of agricultural land were estimated to be seriously affected by soil acidification, with a further 6 M ha vulnerable to this problem. Irrigated cropping industries of the Murrumbidgee and Murray Valleys in southern NSW are primarily rice based farming systems. Whilst rice under flooded conditions is relatively unaffected by soil pH, crops potentially grown in rotation with rice may be significantly affected by low soil pH.

Irrigated cropping systems are under increasing pressure to deliver better water use efficiency. Increasing soil acidity causes reduced yield, leading to reduced water and land use efficiency and a reduced range of crop species that can successfully be grown within the irrigated cropping system. The productivity of irrigated agriculture depends upon the use of significant levels of inputs (water, fertiliser, and chemicals). Constraints to production such as soil acidity must be reduced if optimum use of these inputs is to be attained.

Nitrate leaching, product removal, organic matter accumulation and use of acidifying nitrogenous fertilisers have been identified as contributing to high soil acidification rates in dryland agricultural systems. These processes are probably amplified by the high input/high output nature of irrigated farming systems. Ferrolysis (redox related processes) has been identified as an important process in lowering soil pH in rice growing areas elsewhere in the world. Clear identification of the soil acidifying processes occurring in irrigated cropping industries may allow incorporation of changes to farming systems and practices.

While topsoil (0-10cm) acidity can be corrected by lime application, subsoil acidity is difficult and expensive to treat and as such is a permanent form of soil degradation. Little is known about the degree and extent of subsoil acidity problems in irrigated cropping lands. Subsoil acidity could contribute to productivity losses and represent a significant long term cost to growers for amelioration.

Soils from intensively irrigated farming in southern NSW have been shown to have a substantially lower pH than virgin soil. Increasing soil acidity reduces plant growth and yield, leading to a reduction in water and land use efficiency, as well as limiting the range of crops that can be grown successfully. Little is known about spatial variability of soil acidity or the degree and extent of subsoil acidity problems in irrigated cropping lands.

This project aimed to investigate changes in surface soil acidity over time, and the extent and severity of topsoil and subsoil acidity in irrigated lands of southern NSW. In addition the project aimed to raise irrigator awareness about irrigated soil acidity.

The project examined soil pH changes with respect to soil type and cropping systems in both the topsoil and subsoil. This has been achieved by:

1. Collating existing soil test results for irrigated lands, and 2. A soil-sampling program at accurately located sites (GPS) and analysis for soil pH and exchangeable Aluminium.

Existing soil pH data pH (CaCl2) for the 0-10 cm depth interval from farmers, fertiliser companies and from the NSW Agriculture Soils database was accessed. Existing soil pH data for different irrigation regions in southern NSW was divided into 2 time periods (pre 1985 and 1995-2000) to explore temporal changes in soil pH.

A substantial soil-sampling program was undertaken in the 3 major irrigation areas and districts (Murrumbidgee Irrigation Areas and Districts (MIA), Coleambally Irrigation Area (CIA), and Murray Valley Irrigation Districts (MVID)). Soil sampling sites were identified during discussion with

landholders to sample sites where minimum influence from cut/fill during landforming operations was likely. Fields sampled covered a wide range of crop sequences and soil types.

These data sets were incorporated into a GIS based mapping program to examine the spatial relationships between soil acidity and soil types or cropping systems. Soil types on digitised soil maps for all irrigation areas were assigned to soil types locally amalgamated into soil groups. The soil pH (CaCl2) statistics were summarised for each soil group and linked back to the soil group polygon base map to illustrate the spatial distribution of mean soil pH for each irrigation area.

Results

The soil pH frequency distributions for CIA, MIA and MVID have changed over the pre 1985 to post 1995 time periods and the mean soil pH (CaCl2) of the top 10cm has fallen since 1985. A decrease in the soil pH (ie an increase in soil acidity) of the top 10 cm of soil has occurred since 1985. The decreases in soil pH illustrated here indicate changes in soil pH observed in each of the major rice growing districts, on all soil types and across a range of cropping sequences/ rotations.

For a small number of sampling sites, acidic soil pH levels extend to depth in the soil profile. Results from the current field soil-sampling program including more than 600 sites, in the MIA, CIA and MVID, indicate that 47% of sites had a soil pH (CaCl2) of 5.1 or less in the top 10 cm, and that 31% of sites had a pH (CaCl2) of less than 4.8 in the top 10 cm. For the 10-20cm horizon 16.6 and 10.5 % of sites had pH (CaCl2) of less than 5.1 and 4.8 in respectively.

Extrapolating the soil pH results from known points to a regional scale using existing soil maps shows that based on mean soil group pH, significant areas of the irrigated lands of southern NSW have soil acidity levels which may affect agricultural production. This approach is very rudimentary and needs to be improved in the future.

Table 1. Estimated area of land with mean soil pH (CaCl2) in the indicated classes for the irrigated regions in southern NSW based on sampling program sites.

IRRIGATION DISTRICTS Soil pH MVID CIA MIA (part) (CaCl2) ha (%) ha (%) ha (%) <4.8 0 0 9,534 10.3 0 0 4.8-5.1 536,667 59 44,511 48.1 10,548. 25.7 5.1-5.4 315,204 34.6 37,714 40.8 22,191 54 >5.4 58,371 6.4 749,438 0.8 8,351 20.3

vii

Conclusions

Surface soil pH levels of irrigated soils in southern NSW have decreased over time. Acidification of the topsoil is occurring over significant areas of irrigated land. When the topsoil acidifies, soil acidity begins to increase in the deeper soil horizons. Data from the current sampling program suggests that soil pH in the 10-20 cm depth interval is of concern.

Further investigation is required to identify the predominant soil acidifying processes and to evaluate any management practices to modify the identified process (es).

On-going soil pH monitoring within Land and Water Management Plans will provide a basis to assess soil pH change at a regional scale. Individual growers should undertake regular soil pH monitoring programs with a strategy of evaluating pH by repeated measurements over time at fixed sites rather than field composite samples. Irrigators should be applying lime to address low soil pH conditions and have a liming program to maintain soil pH at an adequate level.

viii

1. Introduction

1.1 Background

The acidification of soils represents a serious agricultural problem in Australia. Within agricultural systems, increasing soil acidity (lower soil pH) results in poor plant growth and reduced yield. Within irrigated cropping systems, soil acidity can lead to reduced water and land use efficiency as well as restricting the range of crop species that can successfully be grown. As a result of increased awareness of the environmental implications of past irrigation practices and changes to water use regulations, irrigation cropping systems are under pressure to reduce groundwater assessions and become more water use efficient. Soil acidity has become a confounding factor in achieving this goal by reducing crop performance and decreasing cropping options.

A survey in the Coleambally Irrigation Area by Dunstan (1984) showed that soil under intensive farming conditions had a substantially lower pH than soil from unfarmed fence line comparison sites. Current soil tests have indicated that the soil pH has continued to decline, however collated soil pH data for the irrigated areas of southern NSW does not exist.

The RIRDC Rice research plans (RIRDC 1999), highlighted that there was a need to address the problem of soil acidity and to develop better understanding of the importance to the rice based farming systems of soil acidity changes. In addition the LWRRDC (199x) indicated that work needed to be done to establish the nature and extent of subsoil acidification as this has implications for irreversible change that could significantly limit production and enterprise options.

Land and Water Management Plans for Berriquin, Cadell, Coleambally, Wakool, and the Murrumbidgee Irrigation Areas and Districts have all identified soil acidity as an increasing problem to sustainable irrigated agriculture. These reports suggest that strategic surveys and reviewing existing soil data bases is required to determine the rate of acidification to maintain versatility in cropping options and prevent subsoil acidification.

1.2 Subsoil acidity

Soil acidification surveys generally refer to soil pH in the topsoil (0-10 cm), although continued ongoing soil acidification can result in a decrease in pH within the subsoil. Subsoil acidity increases the stress to which plants are exposed to and as a result restricts plant growth. Topsoil acidity can be corrected through lime applications, however the amelioration of subsoil acidity can be difficult and expensive and as such represents a permanent form of land degradation, even though irrigators are prepared to deep cultivate

In irrigated cropping systems little is known about the degree and extent of subsoil acidity problems. The dominant irrigated crops and pastures currently grown are not affected by soil acidity. However, if the profitability of these crop types were to change, then irrigators will have a limited range of acid tolerant crops to which they could diversify. Consequently, subsoil acidity contribute to productivity losses and represent a significant long term cost to growers for amelioration.

1.3 Acidification processes

Soils can naturally acidify as they develop, however in many agricultural systems there has been an increased rate of soil acidification. There have been several processes that have been identified as contributing to the high soil acidification rate, the relative importance of each will vary in dryland and irrigated systems. The four processes identified as contributing to the high soil acidification rate in dryland systems include nitrate leaching, product removal, organic matter accumulation and use of acidifying nitrogenous fertilisers. These processes also occur in irrigated farming systems and are significantly amplified by the high input/high output nature of irrigated farming systems.

The rate of soil acidification will vary according to the agricultural production system in use. Dryland cropping systems acidify primarily as a result of product removal and nitrate leaching, build up of soil organic matter and the use of nitrogenous fertilisers are generally secondary factors. In Grazing systems the major causes of acidification is nitrate leaching and build up of soil organic matter. Soil acidity in horticultural systems is mostly located around micro-irrigation outlets. Excess use of acidifying fertiliser, consequent nitrate leaching and product removal, all contributes to acidification in horticultural production.

Irrigated farming systems especially continuously flooded rice growing introduces other processes that may contribute to falling soil pH levels. The process of ferrolysis (Brinkman 1970) has been identified as an important process in lowering soil pH in rice growing areas elsewhere in the world (Kuo and Mikkelson 1979). Ferrolysis occurs during alternating flooding and drying (reduction and oxidation) cycles as occur in rice cultivation. During reduction, provided conditions for microbe growth are suitable, nitrate, iron, manganese and carbon dioxide are used as electron sources and reduced in the process of organic matter decomposition. In the case of iron, the insoluble iron oxides (ferric iron) that occur as a coating on soil particles are reduced to soluble ferrous iron. This form of iron is able to move with water deeper into the soil. Upon aeration of the soil at draining, the ferrous ions are re- oxidised to ferric oxides and the hydrogen produced becomes exchangeable and interchanges with the cations from clay minerals. There is net removal of basic cations from the surface soil and a net increase in hydrogen ions, the cation that causes acidity of the soil. The relative importance of these processes in the irrigated cropping systems of southern NSW needs to be clarified.

Practical management strategies that will reduce the extent and severity of soil acidity for rice and non rice irrigated systems need to be identified and developed in association with farmers.

2. Objectives of the project

• To have increased knowledge of topsoil and subsoil acidity in irrigated lands of southern NSW • To have improved understanding of the impact of soil management (eg landforming) and crop management (cropping sequence and intensity, irrigation management and fertiliser use) on soil acidification mechanisms under irrigation. • To have increased farmer awareness of best practices and systems for soil acidity management that are compatible with irrigation cropping systems. • To reverse of soil acidification before subsoils become acid which will maintain a wide choice of crop species.

3. Methodology

3.1 Soil Mapping

Variation occurs in soil pH values across the irrigated regions of southern NSW in relation to general soil types reflecting variation in soil parent materials viz-riverine c/f. mallee materials. Hence digitised forms of these maps were accessed or digitised for this project into a GIS format compatible with the program ArcView 3.2a.

The soil maps included the southern portion of the MIA, (Van Dijk 1961), soils of part of CIA (Van Dijk and Talsma 1965), the soils landscape map of Coleambally and surrounding lands (Stannard 1982), Berriquin Irrigation District (Smith 1945), Wakool Irrigation District (Smith 1943), East Murrakool, and Lower Murrakool (Churchward 1956, 1958), horticultural soils of the MIA (Taylor and Hooper 1938), Deniboota Irrigation District (Johnstone 1952) and the Jenargo extension of Berriquin (Churchward and Flint) were used as the base soil maps.

Local soil types on digitised soil maps for the irrigation areas (or part therof) were amalgamated into the soil groups. The five main soil groups recognised in the Riverine landscape are: sandhill soils (SS), red brown earths (RBE), transitional red brown earths (TRBE), non-self mulching clays (NSMC) and self mulching clay soils (SMC) (Hughes 1999). The maps were further simplified by dissolving internal soil boundaries to create great soil group polygons, which was used as a base map for further analysis within ArcView 3.2a.

3.2 Collation of existing soil test results

For the period prior to 1985, data from NSW Agriculture Rydalmere Soils database was accessed. Discussion with local district agronomists allowed much of this data to be located to a property level which allowed its incorporation into a GIS with a specified level of accuracy.

Soil pH and exchangeable cation data for irrigated fields in southern NSW on a postcodal basis was accessed from Pivot and Incitec fertiliser companies for the period 1995-1998. From this data it was possible to develop a frequency distribution of soil pH on a Postcode basis.

During the soil sampling program, existing soil pH information was assessed directly from landholders. The Location of the sampling points were identified by growers on to farm maps, which was then located by map co-ordinates so that relationships to soil maps could be ascertained.

3.2.1 Conversion of pH (water) to pH (CaCl2) A regression equation was developed from paired data set of pH (water) and pH (CaCl2) obtained across all soil types and depths in the current sampling program pH (CaCl2) = 1.006pH(water) – 0.79 (r2= 0.91) (n>800). This relationship was used to convert pH (water) data from historical reports to a pH (CaCl2) basis so that comparisons over time could be made.

3.3 Soil sampling program

An extensive soil sampling program was undertaken in the 3 major irrigation (Murrumbidgee Irrigation Areas and Districts (MIA), Coleambally Irrigation Area (CIA), and Murray Valley Irrigation Districts (MVID).

Soil sampling sites were identified during discussion with landholders to confine sample sites to where minimum influence from cut/fill during landforming operations was likely. Fields sampled covered a wide range of crop sequences and soil types. At each sampling site, the cropping history (number of rice crops, length of pasture phases, period since landforming, landforming (cut/ fill), and types and level of fertiliser application, were identified by the landholder and the data recorded on a data collection sheet

3.3.1 Soil sampling Soils were sampled using a 50mm soil coring tube driven into the soil by a combination jackhammer / hydraulic ram sampling rig. At each sampling site, 10 individual cores were taken along a 100m transect. Each core was sub-sampled in 10 cm increments to 50 cm depth. The soil from each depth increment was bulked over the 10 individual cores taken.

The end points of each transect of all soil sampling sites were located in AMG (Zone 55) co-ordinates using a differential GPS.

3.3.2 Soil sample preparation and analysis methods Soils were air dried and ground to pass a 2mm sieve using a jaw crusher. The samples were analysed by a commercial laboratory (Pivotest), for pH (H2O), pH (CaCl2), and EC on a 1:5 soil : water extract, exchangeable cations (Al, Na, Mg, Ca and K) for all depth intervals, and organic carbon and Colwell P in the 0-10cm interval.

3.3.3 Cropping system effects Soil samples from the sampling program were assigned to one of three crop systems categories based on the cropping history obtained for the three years prior to sampling.

These categories are:

• High intensity rice growing ( two to three rice crops grown in the previous three years), • Cropping (with at most one rice crop in the last three years), and • Pasture

3.4 Soil pH mapping

Helyar et.al. (1990) developed soil pH isolines to enclose soils across a range of pH values <4, to >7 by 0.5 unit intervals by assigning soil pH values to the land capability categories of the “Soils resources” map in the Atlas of Australian Resources. The mean value and range were estimated by local district agronomist for each soil type, using soil test records for the district. The area of soils within pH ranges for each mean pH category were calculated with 5.3 million ha of surface soils with pH<4.5, with these soils likely to affected by subsoil acidity. In addition the pH values in the surface soil layers correlated to rainfall and the buffering capacity of the parent material.

MacLaren et.al. (1996) used point kriging within ARC/INFO to create contour maps based on location mean values of soil pH for Victoria.

Ahern et.al. (1992) used soil pH data in conjunction with a 1:10 000 000 soil map of Australia from “A Handbook of Australian soils” to produce a soil pH map for the >500mmm rainfall area of Queensland. The method took into account differences in climate, particularly rainfall to calculate the areal extent of pH categories within three separate rainfall zones. Mapping revealed that there was a strong trend towards increased acidity within higher rainfall zones, and neutral and alkaline soils with the drier areas.

In this project all GPS located soil sample sites were assigned to soil groups by AMG (Zone 55) location using a spatial join to the soil group polygon. The soil pH (CaCl2) statistics were summarised for each soil group and linked back to the soil group polygon base map, polygons with the same mean value were aggregated to illustrate the spatial distribution of mean soil pH for each irrigation area.

The areal extent of land with mean soil pH (CaCl2) in the indicated classes is calculated using ArcView 3.2a techniques.

4. Detailed Results

4.1 Historical results:

There is only limited data is available in the literature concerning soil pH changes over time.

Blackmore et.al. (1956) sampled Gogelderie clay sites to beyond 50 cm and measured soil pHw in 1:5 soil : water extracts. A virgin soil site was identified along with fields that had grown 2, 4, and eight rice crops at that time (1956) (Figure 1). Blackmore et.al. (1956) attributed the slight difference in soil pH to natural variation in the sites in terms of salt, carbonate and clay content rather than any land-use treatment. Soil pHw was converted to pH (CaCl2).

In 1998, soil samples were taken from the same fields to 50 cm in 10 cm increments. Although differences in field locations may confound the comparisons, there appears to have been a sizeable decrease in soil pH at all 3 Gogelderie clay soil rice growing sites to 50cm depth in the profile. This change in soil pH over time suggests a treatment effect. That is irrigation/rice growing has had an effect on soil pH and that effect may extend well down the soil profile (Figure 1).

Loveday et.al. (1978) provides data from a 1966 study of 1:5 soil: water extract data for CIA soil profiles. Soils were sampled in 10 cm increments and of the soils sampled 14% were less than pH 5.1 in the 0- 10 cm interval and 2% in the 10-20 cm interval (Figure 2).

From the literature it appears that in fact little work has been done in irrigated environments on acid soils; or on the processes driving acidification; or on changes that might be necessary in farming systems.

The most relevant work to southern New South Wales is that of Dunstan (1984) undertaken at Coleambally which has a relatively small sample size, consists only of surface soil analysis, has no aluminium data and does not assess subsoil pH levels. This work did however indicate in a fence line comparison that soil pH levels had decreased across a number of soil groups.

-10

-20 T1 0R T1 2R T1 4R -30 T1 8R Depth (cm)

-40 T2 2R T2 4R T2 8R -50 456789 pH (CaCl2)

Figure 1. Gogelderie clay sites with various rice crops grown (Blackmore et.al., 1956) where T1 is 1956 and T2 is 1998 sampling.

Hayman (1989) spells out the processes which have been identified in increasing soil acidity but does not/could not provide detail on just which processes are the most significant in irrigated environments. Willet, Muirhead and Higgins (1979) showed that as well as significant effects on Phosphorus availability - flooding also caused changes in soil pH levels. The majority of the existing work has been restricted to acidification of the surface (0-10cm) layer. The possibility of subsoil acidification is viewed with concern in dryland situations.

9 0-10 cm 10-20 cm 20-30 cm 8 ) 30-40 cm 2 pH = 5.1

Soil pH (CaCl (CaCl Soil pH 5

4 0 102030405060 N o . o f sam p les

Figure 2. CIA soil sites from Loveday 1966.

4.2 Temporal Aspects

Data sets from a variety of sources were accessed and collated these included NSW Agriculture Rydalmere database, District agronomist records, individual farmers, Pivot and Incitec records. This information was organised into an Excel database and used for the following comparisons. The Soil pH 0-10cm in the sampled irrigated fields decreased in all three of the irrigation districts. In the MIA the mean soil pH declined from 6.14 to 5.28 from pre 1985 to 1995-2000. In the CIA and MVID the mean soil pH declined from 5.49 to 5.08 and 5.5 to 5.12 respectively (Table 2).

Table 2. Mean soil pH for all irrigation districts for the two periods, pre 1985 and 1995to 2000.

IRRIGATION DISTRICTS Soil pH MIA CIA MVID (CaCl2) Pre 1985 1995-2000 Pre 1985 1995-2000 Pre 1985 1995-2000 Mean 6.14 5.28 5.49 5.08 5.5 5.12 Standard Deviation 1.10 0.78 0.86 0.81 0.80 0.73

4.3 Comparison of Pre-1985 and Post 1995 soil pH values for irrigation Districts.

Using soil samples from a variety of sources, including the NSW Rydalmere database, DA records, pivot, Incitec, individual farmer records and samples from the project there has been a significant decrease in the top 10cm interval pH occurring in each of the three districts. These topsoil pH decreases are occurring over all soil types.

MIA There has been a decrease in the topsoil pH from 1985 to post 1995 in the MIA (Figure 3). The frequency of the samples less than pH 5.1 (where the soil pH begins to affect plant growth) has increased from 20% to 48% (Figures 3a and 3b). This represents a significant change in topsoil pH distribution within the region.

a. Pre 1985 b. 1995 to 2000 30 30 39% pH < 5.1 58% pH < 5.1 25 25 731 samples 399 samples 20 20

15 15

10 10

Frequency % 5 Frequency % 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2)

Figure 3. Percentage of sites with different soil pH values in the top 10 cm for data available for (a) pre 1985 period and (b) the 1995-2000 period for the MIA.

CIA Figure 4 compares the decreases in topsoil pH in the CIA over the two time periods. Before 1985 (Figure 4a), 38% of samples recorded topsoil pH less than 5.1. In comparison to recent soil tests, the topsoil pH has decreased with 60% of samples being less than pH 5.1 (Figure 4b). The frequency of samples from each time period represents a significant increase in topsoil acidity. With the frequency of soils at risk increasing from 38% to 60%

a. Pre 1985 b. 1995 to 2000 30 30 38% pH < 5.1 60% pH < 5.1 25 25 315 samples 281 samples 20 20

15 15

10 10

Frequency % 5 Frequency % 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2)

Figure 4. Percentage of sites with different soil pH values in the top 10 cm for data available for (a) pre 1985 period and (b) the 1995-2000 period for the CIA.

MVID In the MVID the comparison between the two time periods indicate that topsoil pH is declining and becoming increasingly acidifies. As the pre 1985 frequency of samples (Figure 5a) taken less than pH 5.1 was 39% and post 95 has increase to 58% in 1995 to 2000 time period (Figure 5b)

a. Pre 1985 b. 1995 to 2000 30 30 39% pH < 5.1 58% pH < 5.1 25 25 731 samples 399 samples 20 20

15 15

10 10

Frequency % 5 Frequency % 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2)

Figure 5. Percentage of sites with different soil pH values in the top 10 cm for data available for (a) pre 1985 period and (b) the 1995-2000 period for the MVID.

4.4 Spatial Aspects

4.4.1 Postcodal based Soil pHs The frequency of postcodal based soil pH for the last 5 years was calculated using GIS. For the data that contained coordinates, an overlay of postcodal areas within New South Wales was used to determine the postcode zone that the samples were located in. Samples that did not contain coordinates were assigned postcodes based on a “town” address basis. Other samples included with these graphs include data provided by Pivot and Inctec, which was originally provided in postcodal basis.

MIA Results collected in the MIA were divided into 5 postcodal areas. These included Griffith (2680)(including Yoogali, Willbriggie, Hanwood and Beelbangera) (Figure 6a), Yenda (2681) (Figure 6b), Narrandera (2700) (Figure 6c), Yanco (2703) (Figure 6d) and Leeton (2705)(including Whitton, Wamoon, Murrami and Stoney Point) (Figure 6e). Results indicate that in particular postcode the topsoil is more acidic compared to other local postcode zones. The areas where the topsoil is acidified includes Narrandera, Yanco and Leeton with soil pH values less than pH 5.1 of 68%, 46% and 41% respectively. In comparison the Griffith and Yenda areas have only 13% and 24% of soils sampled less than 5.1.

a. Griffith b. Yenda 35 35 24% < pH 5.1 13% < pH 5.1 30 30 559 samples 123 samples 25 25

20 20

15 15

10 10 Frequency % Frequency Frequency % Frequency 5 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2) c. Narrandera d. Yanco 35 35 68% < pH 5.1 46% < pH 5.1 30 30 426 samples 59 samples 25 25

20 20

15 15

10 10 Frequency % Frequency % Frequency 5 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2) e. Leeton 35 41% < pH 5.1 30 349 samples 25

10 Frequency % Frequency 5

0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2)

Figure 6. Percentage of frequency of postcodes in the MIA with different soil pH values in the top 10 cm for (a) Griffith, (b) Yenda, (c) Narrandera, (d) Yanco and (e) Leeton from 1995 to present including project, Pivot and Incitec results.

CIA In the CIA, the collected data was divided into 2 postcodal areas. These included Darlington Point (2706) (Figure 7a) and Coleambally (2707) (Figure 7b). The comparison in the frequency distribution of soil pH for these postcodes varied considerably as Coleambally had 54% of soils sampled with soil pH less than pH 5.1, while Darlington Point was only 17%.

a. Darlington Point b. Coleambally 35 35 19% < pH 5.1 54% < pH 5.1 30 30 72 samples 695 samples 25 25

20 20

15 15

10 10 Frequency % Frequency % 5 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2)

Figure 7. Percentage of frequency of postcodes in the CIA with different soil pH values in the top 10 cm for (a) Darlington Point and (b) Coleambally Leeton from 1995 to present including project, Pivot and Incitec results.

MVID Within the MVID there were 8 postcode areas in which data was collected and presented in Figure 8. These postcodes included Deniliquin (2710) (Figure 8a), Berrigan (2712) (Figure 8b), Finley (2713) (Figure 8c), Tocumwal (2714) (Figure 8d), Jerilderie (2716) (Figure 8e), Barham (2732) (figure 8f), and Moulamein (2733) (Figure 8g). Within these postcodes, Deniliquin (2710) contains information on the towns of Mayrung, Wakool and Conargo. Whilst Finley (2713) contains information on the town on Blighty. Within the MVID postcodes there are trends of topsoil acidification, these areas include Tocumwal, Berrigan, Finley, Deniliquin, Barham and Jerilderie.

a. Deniliquin b. Berrigan 35 35 35% below pH 5.1 61% below pH 5.1 30 30 1018 samples 283 samples 25 25

20 20

15 15

10 10 Frequency % Frequency % 5 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2) c. Finley d. Tocumwal 35 35 54% below pH 5.1 62% below pH 5.1 30 30 869 samples 294 samples 25 25

20 20

15 15

10 10 Frequency % Frequency % 5 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2) e. Jerilderie f. Barham 35 35 32% below pH 5.1 44% below pH 5.1 30 30 408 samples 48 samples 25 25

20 20

15 15

10 10 Frequency % Frequency %

5 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2) g. Moulamein 35 16% below pH 5.1 30 31 samples 25

10 Frequency % 5

0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2)

Figure 8. Percentage of frequency of postcodes in the MVID with different soil pH values in the top 10 cm for (a) Deniliquin, (b) Berrigan, (c) Finley, (d) Tocumwal, (e) Jerilderie, (f) Barham and (g) Moulamein Leeton from 1995 to present including project, Pivot and Incitec results.

4.5 Mapping Soil Acidity Variation

MIA Figure 9 illustrates the soil acidity risk areas for the part of the MIA, Kooba and Yanco soil maps. The area of soils with average pH between 4.8 and 5.1 is 10,548 ha or 25.7% of the mapped area (Table 3). The area of soils with average pH in the range of 5.1 to 5.4 is 22, 191 ha of 54% of the mapped area.

6200000 405000 410000 415000 420000 425000 430000 435000 440000 445000 6200000 Legend 6195000 Acidity Risk (Soil pH) < 4.8 6195000 4.8 - 5.1

5.1 - 5.4 6190000 Murrami >5.4 #

6190000 # Towns 6185000

6185000 Stanbridge 6180000

## ## Wamoon Whitton # 6180000 Leeton # 6175000

6175000 # Darlington Point Yanco # 6170000 6170000

405000 410000 415000 420000 425000 430000 435000 440000 445000

Figure 9. Soil acidity risk map for the MIA (part).

Table 3 Estimated area of land with mean soil pH (CaCl2) in the indicated classes for irrigated regions in southern NSW based on sampling program sites.

Soil pH MVID CIA MIA (part) (CaCl2) ha (%) ha (%) ha (%) <4.8 0 0 9,534 10.3 0 0 4.8-5.1 536,667 59 44,511 48.1 10,548. 25.7 5.1-5.4 315,204 34.6 37,714 40.8 22,191 54 >5.4 58,371 6.4 749,438 0.8 8,351 20.3

CIA

Soil maps are available to cover the entire CIA. Using the method described for the MIA, an acidity risk map for the CIA was prepared (Figure 10). The areal extent of soil acidity was calculated, with the average soil pH less than 4.8 as indicated in Figure 10 as the “black” areas calculated to be 9,534 ha or 10.3% (Table 3). The areal extent of soil pH within the range of 4.8 to 5.1 makes up 48.1% of the total area, and together 58.4% of the soils are less than pH 5.1.

380000 390000 400000 410000 420000 6160000 6160000

Coleambally 6150000 6150000

# 6140000 6140000 6130000 Legend

6130000 Acidity Risk (Soil pH) < 4.8

4.8 - 5.1

5.1 - 5.4

>5 .4 6120000

# To wns 6120000

380000 390000 400000 410000 420000

Figure 10. Soil acidity risk map for the CIA.

MVID In the MVID, soil maps were available for the entire district. Using described methods the acidity risk map for the MVID is prepared (Figure 11). The areal extent of soils with average soil pH within the range of 4.8 to 5.1 shown in Figure 11 is calculated to be 536,667ha or 59% of the mapped area (Table 3). The areal extent of soil pH within the range of 5.1 to 5.4 is 315,204 ha or 34.6% of the total area.

200000 250000 300000 350000 400000

# MOULAMEIN 6100000

6100000 JERILDERIE SWAN HILL # #

## Legend 6050000

## Acidity Risk (Soil pH) BARHAM # # BERRIGAN < 4 .8 DENILIQUIN

6050000 FINLEY 4.8 - 5.1 WAKOOL 5.1 - 5.4 TOCUMWAL# >5 .4

# To wn s

200000 250000 300000 350000 400000 Figure 11. Soil acidity risk map for the MVID.

East and West Murray valley

Using the easting location of Deniliquin, the data set for the MVID has been divided into two separate areas. East MVID, which includes Finley and Berrigan townships, has a noticeable lower pH to the west MVID, which includes the townships of Wakool and Barham (Figure 12). This highlights that across the MVID there are variations in soil type cropping intensity and other physical factors. However the curve of soil pH distribution shows a similar pattern with a 0.25unit (approx) higher pH in the western Murray valley.

9 West Murry Valley East Murray Valley 8 ) 2 7

5 Soil pH (CaCl

3 0 20 40 60 80 100 120 Sample Number

Figure 12: East-West comparison in the Murray Valley.

4.6 Sub-soil pH Levels

While topsoil (0-10cm) acidity can be corrected by lime application, subsoil acidity is difficult and expensive to treat. The soil pHs ranged from 3.8 to 10.0 with some low pH values recorded to depth in each of the irrigation regions (Figures 13, 15 & 17).

MIA In the MIA the pH range of values showed a wide variety of values with the lowest values of 3.9 at 0- 10cm(Figure 13). However values as low as 4.5 were recorded in the 40-50 cm depth increment. The average soil pH indicates a low soil pH in the surface of 5.2, 5.8 (10-20cm) to 7.1(40-50cm).

0 156 samples

-10

-20

-30 Depth (cm)

-40

-50 345678910

pH (CaCl2)

Figure 13. Soil pH profiles for samples from the MIA, indicating the minimum (- -), mean (-o-), maximum (- -) and standard deviation (I—I) soil pHs observed in sampling program.

The frequency of samples from the MIA in the last 5 years with pH values below the critical values of 5.1 and 4.8 is shown in Figure 14. In the 0-10cm increment 47% of samples taken were below 5.1 and of that 33% were less than 4.8. The subsoil (10-20cm increment) shows that 29% and 20% of samples taken are less than 5.1 and 4.8 respectively.

-10

-20

-30 Depth (cm)

-40 155 samples pH <=5.1 pH <=4.8 -50 0 102030405060 % of sampled sites

Figure 14. Indicate the percentage of sites with soil pH below 5.1 and 4.8 for MIA

CIA In the CIA the pH range of values showed a wide variety of values with the lowest of 3.9 at 0-10cm. The average soil pH 5.01, which is below the 5.1 threshold.

0 50 samples

-10

-20

-30 Depth (cm)

-40

-50 345678910

pH (CaCl2)

Figure 15. Soil pH profiles for samples from the CIA, indicating the minimum (- -), mean (-o-), maximum (- -) and standard deviation (I—I) of soil pHs observed in sampling program.

The percentage of soil samples from the CIA in the last 5 years, shows that 62% of samples (0-20cm increment) were less than pH 5.1 and 46% of that were less than 4.8 (Figure 16). Within the subsoil samples only 22% and 12 % were less than 5.1 and 4.8 respectively in the 10-20cm increment.

Figure 16. Indicate the percentage of sites with soil pH below 5.1 and 4.8 for CIA.

-10

-20

-30 Depth (cm)

-40 50 samples pH <=5.1 pH <=4.8

-50 0 102030405060 % of sampled site

MVID In the MVID the pH range of values showed a wide variety of values with the lowest values occurring in the topsoil at 3.8. The average soil pH indicates a low soil pH in the surface of 5.1, which is at the 5.1 threshold.

0 240 samples

-10

-20

-30 Depth (cm)

-40

-50 345678910

pH (CaCl2)

Figure 17. Soil pH profiles for samples from the MVID, indicating the minimum (- -), mean (-o-), maximum (- -) and standard deviation (I—I) of soil pHs observed in sampling program.

The MVID samples over the last 5 years from this project indicate that 55% of soils sampled were less than pH 5.1 in the 0-10cm increment (Figure 18). Of those samples 34% of the total were less than pH 4.8. In the subsoil (10-20cm increment) only 11% of the samples were less than pH 5.1

-10

-20

-30 Depth (cm)

-40 240 samples pH <=5.1 pH <=4.8

-50 0 102030405060 % of sampled site

Figure 18. Indicate the percentage of sites with soil pH below 5.1 and 4.8 for MVID

4.7 Cropping system effects

Soil samples in from the sampling program were assigned to one of 3 crop systems categories based on the cropping history of the three years prior to sampling. These categories were high intensity rice growing 2/3 rice crops in last three years, cropping upland cropping with at most 1 rice crop in last three years or pasture landuse.

MIA For each of the major irrigated regions the frequency distribution of the soil pH was calculated. In the MIA there were a large percentage of samples that were less than pH 5.1 in all three cropping history groups (Figure 19). The Cropping group had the largest percentage of samples(50% ) taken in the last 5 years being less than pH 5.1. This closely followed by Heavy Rice (45%) and Pasture (40%)

a. Heavy Rice b. Cropping 35 35 45% < pH 5.1 50% < pH 5.1 30 30 116 samples 140 samples 25 25

20 20

15 15

10 10 Frequency % Frequency % 5 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2) c. Pasture

35 40% < pH 5.1 30 38 samples 25

10 Frequency % 5

0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2)

Figure 19.Cropping Systems for MIA.

CIA The CIA samples indicate that the areas classified as heavy rice were extremely acidic with 80% of samples falling into the less than pH 5.1 category (Figure 20). Looking at this figure there are 28% of all the samples for this category less than pH 4.8. These figures are followed by cropping (54%) and Pasture (33%).

a. Heavy Rice b. Cropping 35 35 80% < pH 5.1 30 30 54% < pH 5.1 118 samples 138 samples 25 25

20 20

15 15

10 10 Frequency % Frequency Frequency % Frequency 5 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75

pH (CaCl2) pH (CaCl2) c. Pasture

30 33% < pH 5.1 21 samples 25

10 Frequency % 5

0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75

pH (CaCl2)

Figure 20. Cropping systems for the CIA.

MVID The cropping systems of the MVID reveal a similar trend to the CIA, with the heavy rice system showing the greatest frequency of samples below pH 5.1 (66%), this is followed by cropping (52%) and pasture (43%).

a. Heavy Rice b. Cropping 35 35 66% < pH 5.1 52% < pH 5.1 30 30 151 samples 138 samples 25 25

20 20

15 15

10 10 Frequency % Frequency % Frequency 5 5

0 0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2) pH (CaCl2) c. Pasture

35 43% < pH 5.1 30 88 samples 25

10 Frequency % 5

0 3.75 4.25 4.75 5.25 5.75 6.25 6.75 7.25 7.75 pH (CaCl2)

Figure 21.Cropping Systems for MVID.

4.8 Soil type/ soil texture effects

Loveday (1974) comment that the surface of many soils, after cultivation, are of clay texture and are regarded as clay soils for practical land use purposes. Loveday et al. (1966) provides data on the effective CEC of a range of soils including transitional red brown earth sites that are described as having been cultivated. The depth of cultivation of irrigated soils is frequently to 20 cm.

a. MIA a. MIA 5.1 40 5.1 40

30 Clay 30 Clay

Cultivated Cultivated TRBE TRBE 20 TRBE 20 TRBE ECEC ECEC

10 RBE 10 RBE

0 0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 3.54.04.55.05.56.06.57.07.58.0 pH (CaCl2) pH (CaCl2)

b. CIA b. CIA

5.1 5.1 40 40

30 Clay 30 Clay

Cultivated Cultivated TRBE TRBE 20 TRBE 20 TRBE ECEC ECEC

10 RBE 10 RBE

0 0 3.54.04.55.05.56.06.57.07.58.0 3.54.04.55.05.56.06.57.07.58.0 pH (CaCl2) pH (CaCl2)

c. MVID c. MVID

5.1 5.1 40 40

30 Clay 30 Clay

Cultivated Cultivated TRBE TRBE 20 TRBE 20 TRBE ECEC ECEC

10 RBE 10 RBE

0 0 3.54.04.55.05.56.06.57.07.58.0 3.54.04.55.05.56.06.57.07.58.0 pH (CaCl2) pH (CaCl2)

Figure 22. Figure 23.

Figure 22 and 23 indicate the trend of soil pH values as compared to cation exchange capacity (CEC) for the surface and sub surface samples.

Using these descriptions, indicative soil ECEC values were assigned to the major soil groups (RBE 10, TRBE 20, cultivated TRBE 25 and SMC and NSMC soil 30 meq/100g. Figures 22 and 23 show that ECEC of soil samples below pH 5.1 ranges from 1 to 25 meq/100g. Whilst lower soil pHs are clearly associated with lower ECEC values (lighter textured materials) lower soil pH values are also found to occur heavier textured materials Low soil pH values also occur with materials of ECEC~20meq/100g in the 10-20cm depth interval.

4.9 Exchangeable Aluminium Levels

Figure 24 indicates for the data sets collected the relationship between soil pH and exchangeable aluminium levels. At aluminium levels of greater that 3-5% there can be significant impacts on plant growth and crop yields especially canola, fababeans, lucerne etc.

MIA

25 155 samples

5 5% 3% Exchangeable Aluminium (%) Aluminium Exchangeable 0

3456789 pH (CaCl2 )

Figure 24. Relationship between exchangeable Aluminium and soil pH for the top 10 cm interval for the MIA.

CIA

25 50 samples

5 5% 3% Exchangeable Aluminium (%) Exchangeable Aluminium 0

3456789 pH (CaCl2 )

Figure 25. Relationship between exchangeable Aluminium and soil pH for the top 10 cm interval for the CIA.

MVID

25 240 samples

5 5% 3% Exchangeable Aluminium (%) 0

3456789

pH (CaCl2 )

Figure 26. Relationship between exchangeable Aluminium and soil pH for the top 10 cm interval for the MVID.

5. Discussion of Results

5.1 Project achievement

This project was scheduled to start on the 1st July 1997, but did not commence until March 1998. The first project officer resigned and as a result of difficulties with departmental staff freezes there was a gap of 6 months with the second project officer not commencing until February 1999. The doubling up of training the project officer and aforementioned delays has meant that the project has run 18 months behind schedule. Due to these delays the project has proved to be ambitious.

The original project was aimed at large area farms (rice farms) and the addition of horticultural enterprises was made at the direction of the Acid Soil Action Southern Management Committee, this has added to the workload of the original proposal. The irrigation component of the Acid Soil Action program was reviewed at a meeting of industry and farmers in a meeting at Griffith on the 9th of August 1999. At that meeting recommendations were made to investigate the relationship between soil acidity and dairy farming and soybean growing.

The Acid Soil Action program has recognised these shortcomings and has provided funds to extend this project with an emphasis on the interaction of the project officer with extension staff to identify and extend BMPs on acid soil management in irrigated farming systems.

5.2 Implications

It has been confirmed that low soil acidity is an extensive soil condition in the irrigated rice growing areas of southern New South Wales. This soil acidity occurs over the range of soil types used for irrigated – soil groups of red brown earths, transitional red brown earths, self mulching clays, non self mulching clays and siliceous sands. The degree of acidity recorded in these soils is significantly greater than might be expected from the situation described by Helyar et.al. (1990).

The survey results indicate that many soils have pH levels below 5.1 (CaCl2), and there is clear evidence that the low pH s are being recorded on a range of soil types with a low CEC values (See Figure 22). The survey has identified with GPS locations a large number of sites that can be monitored for future soil pH changes. These sites can be directly linked to irrigation and crop management and fertiliser practices.

Growers need to be aware that soil pH changes are occurring and that although these changes may not impact on their current crop choices , that low soil pH and elevated aluminium levels may restrict the range of alternative crop choice in the future. Growers need to be aware that not applying lime to address falling soil pH levels may not affect the income producing capability of their soils in the short term , low soil pH / high soil aluminium levels as well as affecting crop choice may also affect the capital value of their property in the long term.

Growers need to monitor soil pH levels and address changes (falls) in soil pH progressively by low to moderate applications of lime on a regular basis rather than allowing significant soil pH declines before addressing the issue. Delaying applications may mean that the amount of lime required to address a significant decrease in soil pH may represent a prohibitive cost that will affect the farmers

The expected outcome of this study, increasing our knowledge of the extent of both topsoil and subsoil acidity, in relation to irrigation intensity, soil types and farming systems, will benefit farmers directly

and indirectly by farm advisers have an improved understanding of the relative importance of soil acidifying processes.

Alternative crops to rice such as soybeans, maize, canola, fababeans, wheat and barley clearly have potential within irrigated farming systems however several of these crops cannot handle acid soil conditions. In order to maintain the opportunity to utilise these crops within irrigated farming systems soil acidity must be maintained within an acceptable range. Application of large quantities of lime will be required to modify soil acidity conditions.

6. Recommendations

To ensure increased awareness of soil acidity the results of this project will be integrated into/with existing advisory programs including Southern Irrigated SOILpak, and Irrigated CropCheck programs (Ricecheck, Maizecheck, Soycheck, Canolacheck, Fabacheck, Lucernecheck etc). Awareness of the project outcomes will continue to be highlighted through irrigated crop discussion groups, articles published in the IREC Farmers Newsletter. Results will be made available to commercial advisers, fertiliser companies and fertiliser retailers.

Results of the project be made available for of use to Murray Valley, Coleambally and Murrumbidgee Land and Water Management Plans.

Soil acidity has been identified as an emerging issue for irrigated agricultural production. The current methods of assessing soil acidity consists of collection of random soil samples on a paddock basis to test for soil pH and other nutrients. This approach does not allow for spatial variability within the field and it does not align with precision farming concepts where remedial treatment/ management could be applied to areas smaller than the field scale. There is the need to investigate effective methods of soil acidity assessment on a within field basis by remote sensing techniques or / in addition to targeted soil sampling on the basis of other known factors (yield maps, EM value maps of the field).

6.1 Communication strategy

Findings and awareness raising about this project and its outcomes have been highlighted in the IREC Framers Newsletter, in presentations at rice field days, rice research meetings, NSW Agriculture research/extension liaison meetings. In addition newspaper articles by Matthew Hood (Project Officer), Mary-Anne Lattimore (District Agronomist – Leeton), and regular comments about soil acidity in the local grower newsletter (Agupdate) by John Lacy(District Agronomist – Finley) have provided a means of highlighting soil pH status in irrigation areas.

Soil pH is also a component of the information collected in Irrigated CropCheck data sheets. Presentations concerning the data collected during this project have been presented at Land and Water Management Plan research and development meetings and at the GRDC update series.

As part of the extensive sampling program direct interaction and reporting to individual growers on whose properties sampling was undertaken also represents a significant avenue for communicating the outcomes of this project.

Data from this project has been made available to

• Murrumbidgee Irrigation, Murray Irrigation and Coleambally Irrigation as the implementors of the relevant Land and Water Management plans in their particular jurisdiction • NSW Soils database • National Soil and Water database Information gathered in the project has been collated on a District Agronomist area basis and provided to agronomists as excel spreadsheets

GPS located data will allow accurate re-visiting of sites over time permitting comparisons of soil pH with time across soil types and farming practices in the future.

The Acid Soil Action component of this project has been refunded with an emphasis in the continuing project for extending the results of this project to district agronomists and irrigation officers and to participate in grower crop discussion groups of all district agronomists.

7. References

Beecher H.G. (1992). Soil research in southern New South Wales irrigated farming systems. Proc. Workshop on Soil Research and Sustainable Agriculture in New South Wales. ED. I.C.R. Holford and E.A. Wightman.

Berriquin Land and Water Management Plan (Draft) (1995). Berriquin Community Working Group.

Blackmore, A.V., Talsma, T. and Hutton, J.T. (1956). The cumulative effect of rice growing on two soils in the Murrumbidgee Irrigation Area. CSIRO, Divn Soils, Divnal report 1/56.

Brinkman, R. (1979). Ferrolysis, a soil forming process in hydro-morphic conditions. Department of Soil Science and geology, Agricultural University, Wageningen PUDOC Centre for Agricultural Publishing and Documentation.

Caddell Land and Water Management Plan (Final Draft) (1995). Cadell LWMP Working Group.

Churchward, H.M. (1956). Soils of the East Murrakool district, NSW. CSIRO Aust.Div. Soils and Landuse Ser. No. 19.

Churchward, H.M. (1958). Soils and landuse of the Denimein district, NSW. CSIRO Aust.Div. Soils and Land Use Ser. No. 27.

Churchward, H.M. (1961). Soils of the Lower Murrakool district, NSW. CSIRO Aust.Div. Soils and Land Use Ser. No. 39.

Coleambally Land and Water Management Plan (Draft) (1996). Coleambally LWMP Working Group.

Conyers, M.K. and Scott, B.J. (1989).The influence of surface incorporated lime on subsurface soil acidity. Australian Journal of Experimental Agriculture 29: 201-7.

Dunstan, P. (1984). Coleambally soil survey. Farmers Newsletter Large Area No. 124 pp.16-18.

Dwyer Leslie Pty Ltd (1992).Rice 2000- Environmental Policy Paper. Prepared for the Conservation Committee of the Ricegrowers Association of Australia.

Gillman, G.P. and Sumpter, E.A. (1986). Modification to the compulsive exchange method for measuring exchange properties of soils. Aust. J.Soil Research 24,61-6.

Hayman, P. (1989). Soil acidity - A problem to be aware of. Farmers Newsletter Large Area No. 134 pp 31-4.

Heylar, K.R, Cregan, P.D. and Godyn, D.L. (1990). Soil acidity in New South Wales – current pH values and estimates. Aust. J. Soil Res., 28, 523-37.

Hughes, J.D. (1999). SOILpak for southern irrigators. NSW Agriculture.

Johnstone, E.J. (1952). Soils of the Deniboota irrigation District, NSW. CSIRO Aust. Soils Publ. No. 1.

Kuo, S. and Mikkelson, D.S. (1979). Distribution of iron and phosphorus in flooded and unflooded soil profiles and their relation to phosphorus adsorption. Soil Science 127:18-25.

LWRRDC National Review - Social and Economic Feasibility of ameliorating Soil Acidity.

Loveday, J (1974). Data relating to site of field installation Project CF2 – Hydrology and salinity of a deep clay profile. CSIRO Divn Soils Tech. Mem. 41/1974.

Loveday, J., McIntyre,D.S. and Beatty, H.J. (1966) Field and laboratory data relating to some Colemabally soils. CSIRO Tech. Mem 25/66.

Moormann, F.R and van Breeman, N. (1978). Rice: Soil, Water, Land.International Rice research Institutre, Los Banos, Laguna, Philippines.

Murrumbidgee Land and Water Management Plan On farm options (1995). NSW Agriculture.

National Soil Acidity Workshop Proc. Workshop at El Caballo Resort, Western Australia, 18-21 September, 1995.

Poonamperuma, F.N. (1972). The chemistry of Submerged Soils. In Advances in Agronomy 24:29- 88. Ed. N.C. Brady Academic Press.

RIRDC Rice Five Year Plan 1994-1999.

Smith, R. (1945). Soils of the Berriquin irrigation District, NSW. Coun. Sci. indust. Res. Aust. Bull. No. 189.

Smith, R. (1943). Soils of the Wakool Irrigation District, NSW. Coun. Sci. Indust. Res. Aust. Bull. No. 162.

Stannard, M.E. (1982).Soils of the Coleambally Irrigation Area and adjacent lands. WRC, Leeton.

Taylor, J.D. and Hooper, P.D. (1938). A soils survey of the horticultural soils in the Murrumbidgee Irrigation Areas, NSW. Coun. Sci. Res. Aust. Bull. No.118.

Van Dijk, D.C. (1961). Soils of the southern portion of the Murrumbidgee Irrigation Areas. CSIRO Aust. Div. Soils, Soils and Land Use Ser. No. 40.

Van Dijk, D.C. and Talsma, T (1965). Soils of portion of the Coleambally Irrigation Area. CSIRO Aust. Div. Soils, Soils and Land Use Ser. No. 47.

Wakool Land and Water Management Plan (Draft) (1995). Wakool LWMP Working Group.

Willet, I.R., Muirhead, W.A. and Higgins, M.L. (1978). The effects of rice growing on soil phosphorus immobilization. Australian Journal of Experimental Agriculture and Animal Husbandry 18:270-5.

8. Publications arising from this Project

Geoff Beecher (1998). Identifying and managing soil acidification in irrigated farming systems. IREC Farmers Newsletter, Large Area No 152 pp. 72-3. Beecher HG and Lake B (1999). RIRDC Project Dan 161A Identification and management of soil acidification in irrigated farming systems of southern NSW. IREC Farmers Newsletter Large Area No 154 pp. 63-4.

Lake, Belinda, Beecher, Geoff and Fenton, Greg. (2000). Soil acidity in the Murray Valley Irrigation Districts. GRDC Growers Update. Irrigation - Get the Edge! August 16, 2000, Mathoura. pp. 33-37.

Beecher HG and Lake B (2001). RIRDC Project Dan 161A Identification and management of soil acidification in irrigated farming systems of southern NSW. IREC Farmers Newsletter Large Area No 156 pp. 65-6.

9. Communications/ Extension

Presentations RIRDC Rice Research and Development Committee - Liaison Group meetings 1998, 1999, 2000. RIRDC Rice Research and Development Committee review meetings 1998, 1999, 2000. GRDC Growers Update “Irrigation –Get the Edge!”, Mathoura, August 16, 2000.

Field days Murrumbidgee Farm Fair, Yanco Agricultural Institute, Yanco, May 8-9, 1998 Murrumbidgee Farm Fair, Yanco Agricultural Institute, Yanco, May 7-8, 1999 Henty Machinery Field Days, Henty, 21-23 September, 1999 and Rice Field Day, Yanco Agricultural Institute, 10 March 1999 Murrumbidgee Farm Fair, Yanco Agricultural Institute, Yanco, May 12-13, 2000 Henty Machinery Field Days, Henty, 19-21 September, 2000 and

In addition direct interaction with an estimated

1999 • 250 individuals at Murrumbidgee Farm Fair, Yanco Agricultural Institute, Yanco, 7-8 May 1999 • 200 individuals at Henty Machinery Field Days, Henty, 21-23 September, 1999 and • presentations to approximately 300 individuals at the Rice Field Day, Yanco Agricultural Institute 10 March 1999.

2000 • 250 individuals at Murrumbidgee Farm Fair, Yanco Agricultural Institute, Yanco, 12-13 May 2000 • 200 individuals at Henty Machinery Field Days, Henty, 19-21 September, 2000 and • Murray Irrigation Ltd. (2000). Murray Land and Water Management Plans - Research and Development Workshop, Deniliquin June 21, 2000. • GRDC Growers Update (2000). Irrigation get the Edge! August 16, 2000, Mathoura.

Discussions were undertaken with the Yamma Cropping Group on soil acidity in the southern CIA.

Direct interaction and reporting to some individual growers on whose properties sampling was undertaken.

District Agronomist have been provided with data subsets relevant to their districts in terms of Excel spreadsheet files and ArcView generated maps.