这片干旱地区的土壤表面覆盖着一层坚硬的钙积层。

The dry region's soil is covered with a layer of hard ___caliche.

智利的沙漠地区富含硝石矿（caliche），可用于制造肥料。

The desert regions of Chile are rich in ___caliche, which is used to make fertilizer.