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Scoping study Improving plants’ water use efficiency and potential impacts from soil structure change research investment opportunities CRCIF technical report 3.14/1 RJ Loch CG Grant DC McKenzie SR Raine Cooperative Research Centre Irrigation Futures March 2005
Improving plants’ water use efficiency and potential impacts from soil structure change - research investment opportunities
Disclaimer The information contained in this publication is intended for general use, to assist public knowledge and discussion, and to help improve the sustainable management of land, water and vegetation. It includes general statements based on scientific research. readers are advised and need to be aware that this information may be incomplete or unsuitable for use in specific situations. before taking any action or decision based on the information in this publication, readers should seek expert professional, scientific and technical advice. To the extent permitted by law, the Commonwealth of Australia, Land & Water Australia (including its employees and consultants), the authors, the Cooperative Centre for Irrigation Futures and the National Program for Sustainable Irrigation and its partners do not assume liability of any kind whatsoever resultuing from a person’s use or reliance upon the content of this publication. The National Program for Sustainable Irrigation focuses research on the development and adoption of sustainable irrigation practices in Australian agriculture. The aim is to address critical emerging environmental management issues while generating long-term economic and social benefits that ensure irrigation has a viable future. The Program has 14 funding partners who are: Land & Water Australia (Managing Partner); Sunwater, Queensland; Horticulture Australia Ltd; Goulburn-Murray Water, Victoria; Cotton Research and Development Corporation; Harvey Water, Western Australia; Lower Murray Water Authority, Victoria; Wimmera Mallee Water, Victoria; Ord Irrigation Cooperative, Western Australia; Australian Government Department of Agriculture, Fisheries and Forestry; Department of Natural Resources and Mines, Queensland; Department of Primary Industries and Resources, South Australia; Department of Environment Water and Catchment, Western Australia; and Department of Agriculture, Western Australia.
Submitted to the National Program for Sustainable Irrigation in March 2005 by the Cooperative Research Centre for Irrigation Futures, Toowoomba. © Land & Water Australia 2005. Material from this publication may not be used unless prior written approval has been obtained from the Cooperative Research Centre for Irrigation Futures or the National Program for Sustainable Irrigation. This document should be cited as follows: Loch, R.J., Grant, C.G., McKenzie, D.C., and Raine, S.R. (2005). Improving plants’ water use efficiency and potential impacts from soil structure change - Research Investment Opportunities. Final report to the National Program for Sustainable Irrigation. CRCIF Report number 3.14/1. Cooperative Research Centre for Irrigation Futures, Toowoomba.
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Improving Plants’ Water Use Efficiency and Potential Impacts from Soil Structure Change
Executive Summary Background The Board of the National Program for Sustainable Irrigation commissioned this scoping document to assist in its research investment deliberations. The key questions addressed by this scoping study are: 1. What understanding, techniques and tools require further explanation or development to improve water use efficiency? 2. How well do we understand the impacts of long-term irrigation on soil structure? What are the effects of soil structure change (within and around the root zone on the flow of water and rate of movement along various pathways of salts? Key issues which the NPSI Board requested should be addressed in the document were: • Comment on the place that oxygenation may have in reducing the effects of water logging on production for various irrigation systems and secondary issues such as disease and pathogens at higher water temperatures. • How much is understood on the impacts of soil structure on water use efficiency, and in particular, managing the leaching fraction requirements of various soils? • Comment on the proposed work by Schrale to investigate issues associated with soil structure decline • Other than leaching efficiency and leaching fraction, are there other issues we do not understand that limit plants’ water use efficiency and salt disposal within the root zone? Discussion If water use efficiency (WUE) is considered as the amount of water transpired relative to the amount applied (t yield / ML water) then any factor that restricts the expansion and efficiency of the plant root system will reduce WUE. Given the number of factors shown in the following diagram (and the strong interrelationships between most of the factors at the more detailed two levels), achieving optimal WUE is not a simple task for any irrigation manager. Some factors, such as irrigation scheduling (to optimise performance relative to soil structure and water retention profiles) can provide relatively immediate returns to irrigators. However, other factors such as leaching fraction and efficiency and soil cations are more strategic concerns, as their proper management is essential not for short-term advantage, but rather for the control of medium- to long-term threats to the viability of irrigation at a particular location. The balancing of short-term management needs with longer term strategic concerns is obviously a requirement not only for irrigation managers, but also for organisations involved in irrigation research and development.
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Improving Plants’ Water Use Efficiency and Potential Impacts from Soil Structure Change
Water Use Efficiency
Root function
Soil structure
Oxygenation
Density, strength
Irrigation management
Profile salinity
Cracking, heterogeneity faunal pores
Plant tolerance of salinity
Soil water retention
Sodicity, dispersion
Leaching fraction and efficiency
Irrigation volume
Irrigation timing
Application method
Irrigation water quality
Linkages between the three broad areas impacting on root growth are shown. However, linkages at the most detailed level are too numerous and complex to be indicated on this diagram.
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Improving Plants’ Water Use Efficiency and Potential Impacts from Soil Structure Change
Soil structure and structural decline Soils display enormous spatial heterogeneity at the aggregate and clod scale and over distances
