The database and the methodologies to estimate recent trend of nitrogen (N) and phosphate (P) flows and residual N and P in Japanese national prefectural scales and examples their application
2010
Mishima, S., National Inst. for Agro-Environmental Sciences, Tsukuba, Ibaraki (Japan) | Kohyama, K.
We set a framework of nitrogen (N) and phosphate (P) flow associated with agricultural production and developed the method to calculate N and P flow from the statistical data and questionnaires, then made up a database that describes N and P balance sheet for paddy rice, upland crop, vegetables, orchard, tea and forage and fate of dairy cattle, beef cattle, swine, layer and broiler excreta N and P in each prefecture from 1985 to 2005 in every 5 years. In this paper, firstly we described calculation methods of N and P flows, then made a mini-review of our past works done as the application of this database. National average and prefectural median of N and P balance on farmlands was reduced in accordance to reduction of input of chemical fertilizer without reducing crop N and P productions. Utilization of livestock excreta N and P was reduced in 2005 in spite of increase of non-utilized part. Residual N and P on agricultural production was decreased, however, prefectural maxima increased by intensification of livestock excreta production and minima decreased by lowering chemical fertilizers input. Nitrogen and P surplus was decreased in 2005 comparing with 1985 except vegetables. Vegetables indicated higher surplus in some prefectures than tea that receives the highest N and P on national average. On the other hand, forages indicated N deficiency in some prefectures. Therefore, reduced input of chemical fertilizers for vegetables would be important to reduce prefectural and national N and P surplus. This database can be utile for basic unit to indicate N and P surplus and deficiency with in prefectures minutely. We can also calculate potential of outflow of N and P from farmland to river or ground water, nitrous oxide emission associated with N flow.
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