ABSTRACT
The purpose of this study is to examine and compare different psychological and sociodemographic factors for contracting sweet potato production for farmers with different statuses based upon the theory of planned behavior (TPB). Sustainable production provides contract owners with a sufficient amount of both food crops and a source of bioethanol clean energy. The impact of such factors on potential farmers based on the TPB for a particular contract type is estimated with the data collected in three major sweet potato production cities/counties in Taiwan through the probit model and multinomial logit model. The average size of the surveyed farms is 1.64 ha. The results consistently show that the factors of attitude toward the advantages of contract farming, subjective norms regarding contract farming, perceived contract farming control, and behavior intention have very significant impacts on the selection of contract farming types for professional farmers and brokers. These results indicate that the contract owners will gain the greatest advantage through commanding any factor in TBP for these two groups of farmers, as they have an incentive to manage the sources of sweet potatoes at the best conditions before they have the agreement with the contract owners, either as the supply of bioethanol energy raw materials, supply of food crops, or supply of food processing materials.