High soil sodicity and alkalinity cause transient salinity in south-western Australia

Transient salinity associated with increased dispersion of clays is arguably one of the most economically important soil constraints in Australia because it occurs on land that is regularly cropped. However, this issue is rarely studied. This paper examines the occurrence of transient salinity on agricultural land in the south-west of Western Australia and the factors causing it. We analysed four soil datasets from the region, collected at scales varying from the entire southwest to a single paddock. A variety of soil parameters were correlated with increased electrical conductivity ([EC.sub.1:5]). The most significant relationships were invariably with measures of exchangeable sodium ([Na.sup.+]; 53-85% of variance accounted for), and this factor appears to be most responsible for transient salinity. Another parameter correlated with increased [EC.sub.1:5] was alkalinity. This has been associated with the increased dispersion of kaolinite and consequent decreases in soil hydraulic conductivity; kaolinite is the most common clay mineral in the south-west of Western Australia. Other factors correlated with increased [EC.sub.1:5] were increasing clay, increasing depth in the soil profile and decreasing rainfall. These factors are environmental indicators of transient salinity. Affected soils might be ameliorated by application of agents to increase soil hydraulic conductivity, such as gypsum and/or elemental sulfur. Additional keywords: alkaline soils, clay mineralogy, dispersion, sodic soils. Received 18 February 2015, accepted 26 August 2015, published online 6 June 2016
Introduction Two kinds of soil salinity occur in agricultural areas of Australia (Rengasamy 2002). 'Dryland salinity' generally refers to soil salinity associated with a shallow water table. Typically in this [...]