<P> There was a push for unionization of the farm labor force in the 1960s, with Cesar Chavez (1927--1993), mobilizing California workers into the United Farm Workers organization . </P> <P> In 2015, grain farmers started taking "an extreme step, one not widely seen since the 1980s" by breaching lease contracts with their landowners, reducing the amount of land they sow and risking long legal battles with landlords . </P> <P> New machinery--especially large self - propelled combines and mechanical cotton pickers--sharply reduced labor requirements in harvesting . </P> <P> In addition, electric motors and irrigation pumps opened up new ways to be efficient . Electricity also played a role in making major innovations in animal husbandry possible, especially modern milking parlors, grain elevators, and CAFOs (confined animal - feeding operations). Advances in fertilizers, herbicides, insecticides and fungicides, the use of antibiotics and growth hormones . Significant advances occurred in plant breeding and animal breeding, such as crop hybridization, GMOs (genetically modified organisms), and artificial insemination of livestock . Post-harvest innovations occurred in food processing and food distribution (e.g. frozen foods). </P>

What did the mechanization of agriculture in the united states lead to