The year is 1828 and Mrs. Child's book, The American Frugal Housewife, has been published providing sound household advice gleaned from generations of women before her. She cites: "It is good economy to salt your own beef as well as pork."
For centuries, man knew that salting provided preservation. The Egyptians used salt in the mummification of their dead, wars were fought over salt rights, history shows that salt was used as currency and it was the first disinfectant. Every living plant and animal on earth requires salt to survive, and yet when Matthew 5:13 is quoted, Christians are called the seasoning of the earth, as though our main purpose is to make life more palatable. Belief in Jesus does make life more palatable, but I believe 'our salt' provides a greater purpose.
We are the Preservation of the Earth. Each Christian carries God's Spirit within them; the Holy Spirit. His Spirit, carried inside of us, protects the earth from evil. When Christians pray, they bring the Kingdom of God to earth. The Kingdom of God is contained in our songs of worship and praise. We bring His Kingdom to earth by carrying His Spirit wherever we go.
We are the salt of the earth it is true, but in addition to seasoning, our main purpose is to hold evil at bay through the Spirit that we carry inside.