Association for Public Policy Analysis & Management

A major agricultural challenge facing China over the past decades is the suboptimal use of fertilizer and the negative environmental impacts associated with the overuse. China has been the biggest chemical fertilizer producer and consumer in the world. The national average fertilizer used in China was 342 kg/ha -- 2.5 times higher than the global average. The excessive nitrogen fertilization in Chinese farms presents a multifaceted problem: not only does it fail to significantly improve crop yield, but it also has created serious food safety issues and environmental problems including leaching in ground and lake water and increasing N2O emissions -- a potent greenhouse gas. The adoption of environmentally-sound practices is therefore essential for agricultural sustainability, economic development, and environmental protection. Yet environmentally-sound practices are often adopted slowly, which makes studies that aim to promote their adoption of great importance.

There is growing recognition that social networks play an important role in knowledge diffusion and technology adoption. However, the mechanisms through which information is conveyed by social networks are not well understood. Using data from a randomized experiment in rural China, this study investigates the influence of social networks on the adoption of appropriate fertilizer use and the mechanisms through which social networks operate.

To quantify the network effect, the experiment provides Farmer Field School (FFS) training on fertilizer management to a random subset of farmers in 28 villages in the province of Anhui in China. For untrained farmers, exposure to trained friends significantly optimizes the amount of fertilizer they use, and the optimization gets better when they have more friends who have attended the training. Moreover, the effect of social networks varies with the type of relationship and strength of connections: friendship with trained farmers who are perceived to be the best rice growers by their peer group and long-term friendships with trained farmers have the largest effect on their friends' fertilizer optimization compared to the effect exerted by relations with new friends.

To demystify the black box of the social network mechanisms -- the type of information conveyed by the social network that drives the effect -- I separate knowledge learning from behavior copying. Having expert friends attending the FFS training significantly improves farmers' knowledge of the environmental benefits that accrue from appropriate fertilizer use. Long-term friends are more likely to exert positive social network effect through behavior copying, rather than through diffusion of knowledge on fertilizer use. In addition, I also find that the social network effect is larger when farmers have friends who are more central in the network.

The efficacy of social networks in shaping individual behavior in regard to the adoption of technologies highlights the potential to conduct meaningful interventions without additional monetary or labor resources. Moreover, investigation of the mechanisms through which social networks drive changes in people's adoption behavior provides a promising basis for identifying effective policy interventions. Program management, implementation, performance, and ultimately, impact can be improved by designing training program with well-targeted participants.