What are five major inventions that improved agricultural output between 1750 and 1870?

One of the major inventions that improved agricultural output between 1750 and 1870 are:
- Cotton gin : Eli Whitney invents the cotton gin in 1793, which contributes to the success of cotton as a Southern cash crop.
- iron plow : Jethro Wood invented the iron plow with interchangeable parts in 1819
- Factory-made agricultural machinery (1840s)- this  encouraged commercial farming
- chemical fertilizers were sold commercially (1849)
- Steam tractors are tried out

The answer is a. mantle