Effects of electrical conductivity of water used in wetting and in wet sieving on measured aggregate water stability

Abstract

We investigated effects of electrical conductivity (EC) of water used on determinations of wet aggregate stability by wet sieving. For a cracking clay and a sendy clay loam, deionised water of low EC and tap water of “high” EC (900 μS cm −1) were used to pre-wet air dry aggregates, either by slow wetting at 5 cm tension or by immersion wetting, and aggregates were then wet sieved, again in water of low and high EC. Aggregate stability to immersion wetting was not affected by the EC of the water used in wetting and/or sieving samples. The EC of water used to tension wet aggregates caused significant differences in wet aggregate stability, with, for example, the percentages of 10-5 mm aggregates being 31.5 and 24.4 for the Wallumbilla soil wet by tap and deionised water respectively. For the Pittsworth soil, the corresponding percentages of 10-5 mm water stable aggregates were 35.4 and 25.0. For tension wet samples, wetting rates were not affected in a consistent way by EC of the water used, and we conclude that the differences in aggregate stability were due to effects of the EC of the water on clay swelling. The EC of water used in wet sieving tension wet aggregates affected aggregate stability of one soil, but only when that soil was wetted with water of high EC. We conclude that, for ECs up to 900 μS cm −1, the EC of the water used for wetting samples will be important only when samples are wet slowly, and that the EC of water used for wet seiving will be important only when samples are wet slowly in water of high EC.