Recent changes in food consumption habits of people in developed countries have included a growing demand for a greater variety of value-added products, which, in turn, has given rise to greater sophistication in food processing and distribution systems.  One of the main principle mechanisms that agribusiness uses to secure supplies is contractual relations.  This includes sharecropping, purchase-sale agreements and contract farming.

Procurement methods depend on product type, seasonality, demand, type of grower with whom firms establish relationships, positive or negative experiences from earlier relationships and specific policies point out that land tenure and political conditions of a country also influence decisions.  These factors affect the relationship between firms and their labor force.  There needs to be flexibility which allows regulating the labor supply in line with production cycles and minimization of costs such as health insurance and paid leave.  Firms protect themselves from politically organized labor to ensure a stable workforce.  They do this by practicing sharecropping or contract farming.

http://www.accessmylibrary.com/article-1G1-134777787/agribusiness-and-farmers-mexico.html