What prevented farming from improving after Reconstruction ended?

Old ways of farming and lack of knowledge about commercial farming methods.

Explanation:

Less knowledge about using commercial farming is the factor which prevents improvement in the farming after the end of Reconstruction because the people used old ways of farming which produces lower yield as compared to commercial farming. Many farmers are unable to buy fertilizers due to poor economic condition which occur due to the civil war so lack of knowledge about commercial farming and using old ways of farming are the factors that are responsible for no improvement in farming.

the answer is a) high entry costs