Seasonal changes in soil salinity at Tintinara, South Australia

Abstract

Measurements have been made of seasonal changes in soil salinity and soil water at Tintinara in the Coonalpyn Downs of South Australia. Five separate sites representing different soil profiles were selected for study. All soils contained saline water-tables and four of the five had varying depths of sand over finer-textured subsoils; the fifth soil was fine-textured throughout. The investigations were conducted over a 12-month period, salinity and water determinations being made every 8 weeks. Data on soil salinity are presented as:

(1) Conductance of soil pastes, determined on replicates and statistically analysed.

(2) Percentage of total soluble salts, derived from conductivities of 1:5 soil-water suspensions determined on composite sample.

(3) Percentage of chlorides expressed as NaCl, determined on composite samples.

All sets of data show that soluble salts moved upwards through the soil profile during spring and summer and down during the rainy season. Where the summer water-table was within 4 ft of the surface large amounts of saline material accumulated in the top inch of soil; in one case there was an increase of from 0.019 per cent. NaCl in winter to 3.2 per cent. in summer. Data are also presented showing that the salinity of the ground-waters increased to a maximum of 2-3.5 per cent. total salts in spring or summer. Seasonal soil water changes are recorded and discussed in relation to salinity changes. The climatic, soil, and ground-water factors influencing salt movements are discussed and the agronomic implications of seasonal salinity changes are stressed. Suggestions on the basis of the results obtained are made respecting the sampling of saline soils.