How does social capital influence farmers' adoption of soil testing and formulated fertilisation technology? Evidence from Chinese maize farmers

• Exploring the impact and mechanisms of different dimensions of social capital on farmers' adoption of soil testing and formulated fertilisation technology. • Ecological cognition and fertiliser management knowledge have different mediating effects. • Social capital also has limitations in terms of knowledge diffusion effect that should be emphasized. • Cooperatives partially substitute for social capital and functionally overlap with social network and social participation. • The effect of social capital on soil testing and formulated fertilisation technology adoption shows age and occupation heterogeneity. Soil testing and formulated fertilisation technology (STFFT) plays a key role in the sustainable development of agriculture. Previous studies have suggested that social capital can affect farmers' green production decisions. However, the different dimensions of social capital and the mechanism of its impact on farmers' STFFT adoption are not well understood. Based on survey data from 522 maize farmers in rural China in 2019, this study used the logistic model to empirically examine the effects of social capital on farmers' STFFT adoption, particularly to explore the influence mechanisms. The results indicate that social network, social participation, and social trust positively influence farmers' STFFT adoption. Ecological cognition and fertiliser management knowledge play different mediating roles. Ecological cognition significantly mediates different dimensions of social capital, whereas fertiliser management knowledge mediates only social participation and being asked for advice. Cooperatives partially substitute for social capital and functionally overlap with social network and social participation. Social network, social participation, and proactive consulting play a crucial role in the elderly group, while social participation, proactive consulting, and being asked for advice have significant influences on the non-elderly group. All dimensions of social capital significantly affect STFFT adoption by part-time farmers, whereas only proactive consulting significantly affects pure farmers.