Abstract: Agricultural machinery outsourcing operation service is an important part of Chinas agricultural socialization services, which is important for improving agricultural production efficiency and promoting agricultural modernization. Based on the research data of 975 farmers in Sichuan, Jilin and Jiangsu provinces, this paper empirically tested the influence of social networks on the adoption behavior of farm machinery outsourcing services and its mechanism of action by using Heckman twostage model and mediating effect model. The results showed that in the process of land preparation and harvesting, social networks could not only encourage farmers to adopt agricultural machinery outsourcing services, but also enhance their adoption level. Specifically, for every 1% increase in social networks, the adoption rates of agricultural machinery outsourcing services for farmers in land preparation and harvesting processes could increase by 53.1% and 57.9%, respectively, and the adoption level could increase by 6% and 7.7%, respectively. Different types of social networks had differentiated impacts on the adoption behavior of agricultural machinery outsourcing services by farmers. Vertical social networks had the highest level of impact, every 1% increase could increase the adoption rates of farmers in the land preparation and harvesting stages by 35.3% and 47.4%, respectively, and an increase of the adoption level by 4.5% and 7.5%, respectively. The impact of oblique social networks is secondary, with every 1% increase promoting an increase in adoption rates of 6.8% and 10.8% for farmers in the land preparation and harvesting stages, and an increase in adoption level of 1.1% and 1%, respectively. The impact of horizontal social networks was the weakest, with every 1% increase promoting an increase in adoption rates of 1.8% and 1.3% for farmers in the land preparation and harvesting stages, and an increase in adoption level of 0.1% and 0.1%, respectively. Risk preference plays a partly mediating role in the relationship between social networks and farmers adoption behavior of farm machinery outsourcing services. Accordingly, this paper proposes to cultivate and broaden farmers vertical and horizontal social networks, improve the platform of rural land management rights transfer, and enhance the development level of agricultural service outsourcing market.

Key words: social networks, farm machinery outsourcing operation services, Heckman twostage model, risk preference

摘要： 农机外包作业服务是我国农业社会化服务的重要组成部分，对于提升农业生产效率和促进农业现代化具有重要意义。基于四川、吉林和江苏3省975份农户的调研数据，运用Heckman两阶段模型和中介效应模型，实证检验社会网络对农户农机外包作业服务采纳行为的影响及其作用机制。研究结果表明：在整地和收获环节，社会网络可以促使农户采纳农机外包作业服务，还会提升其采纳程度。具体来说，社会网络每提高1%，整地和收获环节农户农机外包作业服务采纳率分别可提高53.1%和57.9%，采纳程度分别可提高6%和7.7%。不同类型社会网络对农户农机外包作业服务采纳行为会产生差异化影响。纵向社会网络的影响程度最高，每提升1%可促使整地和收获环节农户采纳率分别提高35.3%和47.4%，采纳程度分别提高4.5%和7.5%；斜向社会网络的影响程度次之，每提升1%可促使整地和收获环节农户采纳率分别提高6.8%和10.8%，采纳程度分别提高1.1%和1%；横向社会网络的影响程度最弱，每提升1%可促使整地和收获环节农户采纳率分别提高1.8%和1.3%，采纳程度分别提高0.1%和0.1%。风险偏好在社会网络和农户农机外包作业服务采纳行为的关系中起到部分中介作用。据此提出：培育和拓宽农户纵向、横向社会网络，完善农村土地经营权流转平台，提高农业服务外包市场发育水平。

关键词: 社会网络, 农机外包作业服务, Heckman两阶段模型, 风险偏好