Habitat heterogeneity and dispersal limitations have been shown to cause β-diversity (diversity among local communities) and maintain regional species diversity, but this issue has rarely been examined for Japanese agricultural lands. Here, we estimate the amounts and causes of β-diversity in herbaceous communities in a study site consisting of traditional terraced paddy fields and nearby grasslands in Shizuoka Pref., Japan. The paddy levees and the grasslands have been mown five times and once per year, respectively. Each covers of herbaceous species (measured in 0.25 m² quadrats) and soil properties (water content, hardness and pH) were measured in the paddy levees (66 quadrats) and the grasslands (61 quadrats). The SLA (specific leaf area) of each species was also measured. Diversity partitioning revealed that between-habitat types and between-quadrats β-diversity constituted 30% and 60% of the observed diversity, respectively. Between-habitat types β-diversity partly reflected a high occurrence of annual and high SLA species in the paddy levees. Species dissimilarity between quadrats was positively associated with both differences in soil hardness and spatial distance, suggesting that species sorting along a soil hardness gradient and dispersal limitation might cause the between-quadrats β-diversity.