Factors controlling organic amendment application rate and long-term change in application rate in Japanese paddy field using longitudinal questionnaire survey dataset (the Basic Soil Environment Monitoring Project, Stationary Monitoring, 1979-1998).

摘要

Using data from a longitudinal survey (the Basic Soil Environment Monitoring Project, Stationary Monitoring, 1979-1998, launched by the Ministry of Agriculture, Forestry and Fisheries of Japan), it was found that livestock possession, soil type, utilization form of paddy fields and full-/part-time status of farmers were important factors controlling application rates of organic amendments (OA) in Japanese paddy fields. When data points were categorized in terms of these four factors, application rate of livestock waste compost (LWC) on the basis of fresh weight (FW) varied remarkably. Application rates of LWC decreased during the survey period, whereas rice straw residue (RSR) application rates increased. The smallest LWC application rate (average 0.3+or-0.2 Mg FW ha-1 for the period between 1994 and 1998) was found among rice (Oryza sativa L.) single-cropping, poorly drained lowland paddy soils (PDLPS) including Histosols, with full-time farmers possessing no livestock. Even among rice single-cropping, the application rate was clearly larger (average 10.6+or-0.5 Mg FW ha-1 for the period between 1979 and 1983) for non-poorly drained lowland paddy soils (non-PDLPS), with full-time farmers possessing livestock. Much greater than this was the LWC application rate for converted paddy fields (average 29.9+or-4.3 Mg FW ha-1 for the period between 1989-1993), non-PDLPS, with full-time farmers possessing livestock. Accordingly, this study emphasizes the importance of categorizing data points at least in terms of soil type, utilization form of paddy fields, livestock possession and part- or full-time farming status when constructing an inventory, exploring changes in OA application rate, and making policy.