Y= 5.42 +0.52X (p<0.01)

1. 140-19: Evaluation of Japanese Agricultural N and P Management by Integrated Environmental Impact Indicator in 1990 and 2005. Results and discussions Reduce to STD condition y = 265 + 6.09e-5x R= 0.482 (p<0.01) y = 4030 + 0.000867x R= 0.522 (p<0.01) y = 259 + 3.72e-5x R= 0.337 (p<0.01) y = 5100 + 0.000592x R= 0.343 4 5 1.5 10 3 10 TP-Real TP-STD TN-Real TN-STD 4 5 1 10 2 10 P in river water (Mg) N in river water (Mg) 5 5000 1 10 0 0 7 8 7 8 8 0 5 10 1 10 0 5 10 1 10 1.5 10 P-load potential N-load potential Mg N2O-N Potential of N leaching (ppm) Y=5.42+0.52X (p<0.01) 25% cut B A % of wells excess STD 4 5 10 4 4 10 4 3 10 IEI in 2005 IEIin 1990 4 2 10 4 1 10 D C 0 1990 Relative change of IEI IEI is higher in central Japan in both year (Fig 2 A,B). This trend is not same as N and P surplus. Numbers prefectures increased IEI was larger than reduced (Fig 2 C), although N and P surplus was generally reduced in 2005 than 1990 (Mishima et al. 2009, 2010, submitted a). Composition of IEI is indicated in Fig. 2D. Prefecture where IEI is mainly consisted with risk ground water pollution and N2O emission had is basically low IEI value and if prefectures where IEI contains high P and N load potential to river water indicate high IEI. Therefore, increase of IEI might be caused by increase of soil available N and P in 2005 than 1990 in prefectures. S. Mishima and K. Kohyama Nat. Ins. Agro-Env. Sci. Jpn Introduction Set the target, weighting each impacts and integration The targets were set as i)2ppm N and 0.1ppm P in river water as tentative target, ii)5.42ppm N that no well will expected to be excess water quality standard (10ppm N) and iii) cut 25% of N2O against 1990 by policy aim in each prefecture. Regression coefficients when river water P and N concentration is standardized as above (STD) was smaller than when real river water P and N concentration is set as 61% for P and 68% for N (Fig 1 A, B: purple dots). Weighting factors are 1.6 for P indicator (inversed value of 61%), 1.5 for N indicator (same as P), present potential of N leaching divided in each prefecture by 5.42 on risk of ground water pollution, and 1.3 (inversed value of 75%) for N2O emission in each prefecture. Integration as IEI was done in the below formula. Agricultural nitrogen (N) and phosphorus (P) use sometimes cause various negative environmental impacts. We set negative impacts as i) N and P load potential to surface water by erosion, ii) risk of ground water pollution by nitrate, and iii) contribution to global warming by nitrous oxide (N2O) emission, then estimate each negative impacts (Mishima et al. 2009, Mishima and Kohyama in review a,b). We found out that higher/lower negative impacts is not always caused by higher/lower N and P use or surplus in prefectural basis in Japan. To evaluate total negative impact in regional basis, building up integrated single indicator for environmental impact (IEI) would be necessary. For this purpose, we applied distance to target (DtT) method. In this poster, we indicated distribution of IEI and evaluated cause of regional higher IEI in Japan. 1990 (kgN/ha) 1990 (kgP/ha) Method Present state P and N load (P and N indicator), N leaching potential and N2O emission was calculated by the formulas listed below. P and N indicator summarized watershed scales were significantly correlated with amount of P and N flow at the water quality monitoring points of the watersheds (Fig 1. A, B, blue dots). N leaching potential in prefectures significantly correlated with % of observation wells that excess water quality standard in the prefecture (Fig 1. C). N2O-N emission was estimated to be 48GgN in 1990 (Fig. 1. D) A B C D Fig.2 IEI distribution and its change and composition Conclusion 1) High N and P surplus is not always caused high IEI. The other environmental conditions such as erosion potential and precipitation 2) Weight of P and N load potential might be important than risk of ground water pollution and N2O emission and are affected by soil available N and P. S. Mishima, A. Endo, K. Kohyama (2009) Recent trend in residual nitrogen on national and regional scales in Japan and its relation with groundwater quality, NUTRIENT CYCLING IN AGROECOSYSTEMS, 83(1), 1-11 S. Mishima, A. Endo, K. Khoyama (2010) Recent trends in phosphate balance nationally and by region in Japan, NUTRIENT CYCLING IN AGROECOSYSTEMS, 86(1), 69-77 Fig.1 Present state and emission target