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

Article 3.4 of the Kyoto Protocol stresses that agricultural soils can contribute to sequestrate greenhouse gas and thereby help countries to comply with their commitment under the Kyoto Protocol to the United Nations Framework Convention on Climate Change. From this perspective, organic amendment (OA) application is widely accepted as one of the agricultural managements that increase soil organic carbon in crop land. Hence, long-term knowledge of OA application rate has become increasingly important, as it helps to understand SOC stocks and changes, and to estimate them using models (e.g. the Rothamsted carbon model). This paper described long-term OA application rate and examined influences of combinations of some factors (i.e. fruit tree orchards, livestock possession), on OA application rate, using questionnaire survey to farmers. It was found that total OA (livestock waste compost, LWC and Other OA, e.g. rice straw residue) decreased from 8.4 (1979-1983) to 5.7 (1994-1998) Mg fresh weight (FW) ha^-1. The proportion of farmers that applied total OA decreased from 56 % to 39%. Average OA application rate differed depending on cultivation of fruit tree orchards, livestock possession and part/full-time status of farmers throughout the survey waves. When data points were categorized into several distinct groups according to joint influence of fruit tree orchards and livestock possession, there was about six times difference between the largest (13.3 ±5.1 Mg FW ha^-1, Japanese pears with livestock possession), and the smallest (2.2±0.3 Mg FW ha^-1, oranges with no livestock possession) LWC application rate in a survey wave that includes the base year under the Kyoto Protocol (1989-1993).