The €4.2 billion ($6.5 billion) company is the world's largest salt producer and one of the top global suppliers of potash for use in fertiliser.
K+S, which has projects in three continents, said Western Australia was a "perfect target" for its salt growth strategy because of the region's history of salt production and proximity to Asia.
"When we look at the global demand for salt we see Asia as being the largest-demand market and the market in which we are not significantly participating so in many respects it is a white spot on our map," K+S Group board member and salt business head Mark Roberts told Fairfax Media.
"We recognised the need to have production that would enable us to be more sustainably competitive in the growing Asian market, specifically for chemical salts."
The Ashburton Salt project is on the coast about 40 kilometres south-west of the town of Onslow, and is expected to produce about 3.5 million tonnes of salt a year at a development cost of about $350 million.
It is still in the early stages of development, with a final investment decision slated for 2019. If the project went ahead, K+S would join other Pilbara salt producers, including Rio Tinto and Japanese trading house Mitsui & Co.
According to the West Australian Department of Mines and Petroleum, 11.4 million tonnes of salt, worth $355 million, was produced in the state in 2015.
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