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 © 2004 Rural Industries Research and Development Corporation. All rights reserved. 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 ii 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 iii 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. iv 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 v 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.