Method 4021 Framework

The framework of the study is set out in Fig. 40.1. The livestock sector includes cattle, pigs, and poultry. Because numbers of other livestock, such as horses and goats, are few, they were ignored. The crop sector includes paddy rice, upland fields, vegetables, tea, orchards, and forage.

Volatilization

Livestock excreta

f i M

Composting and storage

Deposition Dispose

Manure Chemical fertilizer

Local land

Farmland

Local land

Farmland

Direct emission Indirect emission ^ Nitrogen flow ,

Infiltration

Fig. 40.1 Framework of N2O emission associated with agricultural N flow. 40.2.2 Data sources

Basic statistical data, such as livestock numbers and areas of planted crops, were obtained from the Statistical Yearbook of the Ministry of Agriculture, Forestry, and Fisheries (MAFF 1986b, 1991b, 1997, 2002b, 2006b, 2007).

Chemical fertilizer nitrogen (N) applications for each crop type in 1985 and 1990 were derived from the results of MAFF questionnaires from 1981 to 1989. MAFF Production Environmental Statistics for 1997, 2002, and 2003 (MAFF 1998, 2002a, 2003) were used to derive chemical fertilizer applications in 1995 and 2005. The average values were applied to 2000.

Basic units of livestock N excrement were derived from Tsuiki and Harada (1997), and N volatilization rate during composting and storage was derived from Mishima et al. (2008). Rate of excreta use and disposal was calculated from MAFF Cost of Livestock Products (MAFF 1986a, 1991a, 1996, 2001, 2006a) and Association of Livestock Production (1999). The amount applied to each kind of crop was calculated from the total amount of excreta used, and the amount applied to each kind of crop as a percentage of the total was calculated from results of MAFF questionnaires and Production Environment Statistics on chemical fertilizer use for each year.

The N2O emission factor during composting and storage was derived from the IPCC default value (GIO, 2007). Factors for direct emission from farmland were calculated according to Akiyama et al. (2006), while those for indirect emissions were found according to IPCC default values (GIO, 2007).

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