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Osmotic and ionic effects of various electrolytes on the growth of wheat

Pichu Rengasamy
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Soil and Land Systems, School of Earth and Environmental Sciences, The University of Adelaide, Waite Campus, PMB 1, Glen Osmond, SA 5064, Australia. Email:

Australian Journal of Soil Research 48(2) 120-124
Submitted: 26 April 2009  Accepted: 21 October 2009   Published: 31 March 2010


Pot experiments were conducted using a sandy loam soil and various electrolyte solutions such as NaCl, CaCl2, Na2SO4, and Hoagland nutrient solution containing all macro- and micro-nutrient elements in appropriate proportions, inducing different electrical conductivity (EC) levels of the soil solution during the growth of Krichauff wheat while the water content in the pot soils was maintained at field capacity. The resulting differences in dry matter production after 40 days of growth clearly indicated the continuous operation of osmotic effect as the EC of the soil solution increased from 0.7 to 41.0 dS/m. However, the osmotic effect became dominant and severely restricted plant growth when the soil solution EC increased above a ‘threshold value’, which was 25 dS/m, corresponding to an osmotic pressure of 900 kPa, in this experiment. Below this EC value, particularly at low EC values, ionic effects due to Na+, Ca2+, SO42–, and Cl were also evident, but it could not be concluded whether these effects were due to toxicity or ion imbalance. The osmotic effect at EC values above the threshold resulted in greatly reduced water uptake from pot soils, the unused water being in the range 89–96% of the field capacity of the soil. Water use efficiency is a major factor in profitable and sustainable dryland agriculture. Both soil management and selection and breeding of salt-tolerant plants should concentrate on ensuring that the threshold EC value for severe osmotic effects is not reached under field conditions.


The author thanks the Grain Research and Development Corporation of Australia for continuous financial support for the project reported in this paper, his colleague Ms Alla Marchuk for the technical help and Mr Ehsan Tavakkoli (PhD student) for the help in statistical analyses.


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