Factors Controlling Organic Amendment Application Rate and Long-Term Change in Application Rate in Japanese Upland Field Using Longitudinal Questionnaire Survey Dataset (the Basic Soil Environment Monitoring Project, Stationary Monitoring, 1979-1998).

In order to increase knowledge on organic amendment (OA, livestock waste compost (LWC) and “other OA”) application rate which is crucial in understanding long-term change in soil organic carbon, we used activity data, derived from questionnaire survey to farmers, on Japanese upland field (1979-1998). Average OA application rate (fresh weight, FW) decreased from 20.9±0.5 (1979-1983) to 14.5±0.4 (1994-1998) Mg FW ha^-1. Although difference between/among levels in a factor became smaller, OA application rates were influenced by crop types, livestock possession and part/full-time status of farmers throughout the survey waves. Particularly, crop type had the most significant influence. When data points were categorized by the factors, there was about nine times difference between the largest (41.8±2.5 Mg FW ha^-1, “forage and/or fodder crop (FFC)” with livestock possession full-time farmers), and the smallest (4.5±0.4 Mg FW ha^-1, neither FFC nor vegetable cropping with no livestock possession full/part-time farmers) LWC application rate in a survey wave (1989-1993) that includes the base year under the Kyoto Protocol. The largest decrease rate in LWC application in the twenty years was in groups of vegetables with livestock possession full/part-time farmers.