Appendix III - Impressions From the Sodicity Conference

Dr Bob Sojka

USDA/Agricultural Research Service
Northwest Irrigation and Soils Research Lab
3793N-3600E, Kimberly, ID 83341, USA
PH 208-423-6562, FAX 208-423-6555

In January of this year I arrived for a two month visit of Australia, on a mission to assess the nature and extent of irrigation-induced erosion, its impact on surface water quality and the feasibility of using chemical polymers to help alleviate these problems.  Mv visit coincided with the Sodicity Conference held in Tatura, Victoria, from 28 February through 1 March, and since I was not a formal conference participant its organizer, Dr. Aravind Surapaneni, asked if I could offer comment from, what he termed "an objective and unbiased viewpoint."  While being humbled by a suggestion to offer comment on the contributions of so many fine scientists in a field in which I have only had a small personal role, I was also eager for the chance to offer comment on a topic that, as my own fact finding trip confirmed, is so central to the future fate of Australian agriculture.  Sodicity is especially important to Australia's irrigated agriculture and its surface water ecology and its terrestrial and riparian management.

"Awareness" may be the word that best sums up the issue of greatest public importance, and it did not take long to surface at the conference.  Several speakers noted that many Australian land managers are still unaware of the extent and potential severity of their country's soil and water salinity and sodicity problems.  This may be related to the fact that the ambitious development of large irrigated tracts has been a relatively new occurrence and that even on tracts established in the 1950s and 1960s it has taken several decades for sodicity and salinity problems to manifest themselves.  The problem of awareness takes on an even greater urgency now as wi despread conversion from rainfed pasture and grazing lands, following a market-driven decline of the sheep and wool industry, is prompting many landholders to convert their operations to irrigated cropping.  Many of these "new farmers" are unfamiliar with basic "on farm" aspects of soil chemistry and soil physics - even to the extent of not distinguishing the difference between salinity and sodicity.  Indeed, it is not merely a farmer problem, as water quality criteria in some water management schemes are based solely on salinity, i.e. electrical conductivity management.

Water blending ("conjunctive water use" in American terms, or "shandying" in Australian terms) was identified as another major issue.  Perhaps the issue is better framed as blending vs separating of relatively high quality primary water sources and saline, sodic, or saline/sodic waters from field tile drains or deep wells.  The rationale for blending is to increase the total volume of water available by diluting problem waters with relatively high quality waters.  The rationale for segregating impaired water from high quality water is to limit the extent of soil salinization and sodificatioia to a minor fraction of the total land area irrigated - and in so doing limit the extent of land that requires special and higher order management.  The logic of each approach was explored by several speakers.  The conference keynote speaker, Dr. James Oster challenged the conference to consider the desirability of creating a system of monetary incentives based on acceptance of impaired water, thereby encouraging segregation and limitation of the extent of salt impairment of primary agricultural lands.  A third unique, and certainly controversial idea, was the suggestion by Dr. Arie Nadler that the pervasive use of gypsum to combat sodicity may have become more widespread and frequent than is warranted by documented yield results.  Further, he noted that solubility as influenced by common ion effects and evidence from mass balances in leaching studies suggests that not all calcium added via gypsum remains available in soil solution to affect the calcium/sodium balance of the soil exchange complex.  His thesis, stemming from this caution against what he termed "gypsomania" was relatively simple: Gypsum is applied for two reasons, to reduce direct sodium impairment of plant growth and to improve infiltration - if there is no crop response to gypsum, then other infiltration-enhancing practices should be used and further gypsum additions might well be curtailed.

An issue whose importance is obvious to anyone who has looked down on Australian waters from an airplane is the role of sodicity in soil dispersion and runoff turbidity.  The dispersive properties of sodium, related to the ion's hydrated radius and its relative inability to shrink the electrical double layer surrounding suspended clay particles plays a major role in soil erosion, infiltration impairment and transport and desorption of nutrients and pesticides from suspended soil into surface waters.  Clarifying Australia's surface waters, estuaries or coastal waters and reducing their pesticide and nutrient contamination will be linked to managing soil and runoff water sodicity.  This issue also has significant implications for rice production, which suffers severe stand reduction and maturity delay when water turbidity impairs photosynthetic light penetration and lowers temperature in paddy water.

These and many other technical issues were explored in the conference.  The level of technical competence of the presenters and the quality of their work must be commended.  I was gratified that more than one speaker noted that when studying salinity and sodicity one must keep in mind that outcomes and effects of treatments and management strategies are dependent on long lists of interactive and sometimes subtle but important factors - physico-chemical, biological, system architecture and operations related, societal, economic etc.  In the soil alone, mineralogy, organic matter, iron chemistry, cropping system artifacts and climate all need to be appreciated and accounted for to understand or predict the influences of salinity and sodicity.  Finding a normalization rationale to evaluate what has been learned from one set of circumstances for use in Australia is no small part of the challenge facing Australian soil scientists, agronomists and engineers.

If there were any aspect of the conference that may have been improved it might relate to this latter issue, which is really a statement of the need for "perspective." The Sodicity Conference provided a top-notch forum among sodicity experts - soil scientists, water and agricultural engineers and even a few policy makers.  Absent were influential farmers or representatives of the popular environmental community.  It might have been better to have heard from the policy matters at the end of the conference, after they had had the benefit of the scientific presentations.  And the scientific presentations might have had more impact if grounded by a questioning audience of other than, largely, scientists and engineers.  These are small deficiencies for so well organized and so high quality a scientific conference, and are meant more as a reflection than a criticism.

Science seems to be losing some of its allure and emotional authority in this new world of ours, where toddlers are weened on gigahertz microprocessors.  We are all so used to technology and 'I take it so for granted that we forget that before technology comes knowledge.  Certainly if we are to convince governments and other funding bodies of the need to do research and the need to transfer technology to users and to policy makers we need first to educate them and engage them in the dialogue (at the risk of being educated ourselves).  Accomplishing this kind of interaction is a common oversight in scientific communities.  It makes us uncomfortable and sometimes it takes a real effort to establish genuine cross communication among scientists and the public.  I would argue, however, that in this "information age" (misinformation age?) the old traditional patterns of dealing with environmental problems from within the scientific infrastructure need some rethinking.  The benefits of inclusivity are potentially considerable, and we as scientists will probably be surprised at how astute the lay public can be at assimilating the knowledge we present them, if it is indeed relevant to real problem solving.  Perhaps the conference proceedings can be "translated" for broader dissemination to the public through a final act of "extension." And perhaps at the third sodicity conference, which I definitely want to attend, we can all enjoy presentations and panel participation aimed at and drawn from our customers in the farming and environmental communities, as well as from our colleagues at the bench.

All in all, I commend the conference organizers and sponsors on a job very well done.  The topics explored and the technical challenges presented by conference participants will chart a path of scientific investigation lasting several years.  One of the best indicators of a great conference is one that sends the participants home with more questions than answers.  The sodicity conference met this test, and its organizers and sponsors are to be commended.

NOTE: This article is published in official newsletter of the Australian Society of Soil Science Inc (ASSSI), Profile - issue 122, April 2000.