1822  (1960)  . . . he had just exchanged her [a mare] with a couple of tons of salt hay, for an excellent young horse. . . .
1934  "It's salt hay," said the driver. "Oxen and cattle like it for a relish. We gather it from the meadows near the salt water. Salt hay is different from English hay. It has to be dried and dried and dried."
1963  The swamp was lush with rank grass, known as salt hay because the water of the swamp was brackish.