The electoral college has determined that two candidates have tied for president what happens next ?

In this case, the House of Representatives votes for the president - this was decided by the 20th Amendment. The house votes for one of the three candidates with the highest number of electoral votes (if more than 2 got some votes).

The changes to agriculture in the united states since 1900 is that increased mechanization has increased food production, thereby increasing the need for labor. there has been an increased need for higher speeds of food production due the fact that the population in the united states continues to rise.