A previously unheralded form of soil salinity can affect crop yields across large areas of the SA grainbelt, and in other states.
The University of Adelaide’s Pichu Rengasamy said that transient salinity differed from seepage or dryland salinity, which occurred when watertables rose bringing salt nearer to the soil surface.
"Many soils naturally contain salt in the top 1-2 metres, held there by impervious clay layers. When the soil dries out, the concentration of salt increases and moves up the profile affecting plant growth — this is transient salinity. We believe about 30 per cent of the cropping land in SA is affected."
(Note: In some areas like the Eyre Peninsula, farmers know a kind of salinity as ‘magnesia patches’. The difference between ‘magnesia patches’ (which incidentally have nothing to do with magnesium) and transient salinity is that in magnesia patches salt appears on surface soil, whereas transient salinity occurs in subsoils.)
Dr Rengasamy said that trying to find ways to get salt to move deeper and away from the cereal root zone in these soils would be very difficult, so in the short term, plant breeding solutions were the best option.
This work is being undertaken at Adelaide University by Tony Rathjen and colleague David Cooper, who are concentrating on producing salt tolerance in durum wheats, regarded as the most susceptible to transient salinity. Rana Munns at CSIRO Plant Industry in Canberra has developed three salt-tolerant durum lines used in the breeding program. (See Ground Cover issue 30.)
"At the same time we are looking at bread wheats which might be more tolerant to salinity than Krichauff, which is the most tolerant commercial variety available," Mr Cooper said.
Dr Rathjen said until more salt-tolerant varieties were produced, there was little growers could do other than avoid growing durums where transient salinity was likely to occur.
Contact: Dr Pichu Rengasamy, Dr Tony Rathjen or Mr David Cooper 08 8303 4455