Agriculture accommodates human resources of varying educational qualifications and skill sets. At the very top of the intellectual ladder, agriculture accommodates agricultural or crop scientists. Chemical engineers also play a big role in agriculture through development and production of fertilizers, pesticides, etc. Mechanical engineers manufacture equipment and tools used in agricultural activities. At the other end of this ladder, semi-skilled or unskilled labor is also absorbed in agriculture, often as seasonal workers. Seasonal employment accommodates millions of people around the world. Seasonal agricultural opportunities are mostly available during harvest times. Agriculture also accommodates entrepreneurs, people who own and manage large farms and generate appreciable income (typically $500k/yr or more in the US).
Please note that introduction of machinery in agriculture reduces the direct human involvement in the field, however it accommodates human resources in the development, manufacturing and maintenance of such machines.