I believe it is supply shock
Answer:
“When We Worked on Shares, We Couldn't Make Nothing”: Henry Blake Talks About Sharecropping after the Civil War. ... By 1870, sharecropping was the dominant means by which African Americans could gain access to land in the South.
Explanation: I hope this helps, if not friend I tried :)
The law you seek is the Emancipation Proclamation, but you should google it to see what the strings were that were attached to this bill.