Nitrogen and phosphate balance on crop production in Japan on national and prefectural scales

Abstract

Trends in nitrogen (N) and phosphate (P) balance for several crops were calculated for the nation and by prefecture for 5-year periods from 1985 to 2005. Prefectural chemical N and P fertilizer applications for paddy rice and upland crops declined but applications for vegetable crops increased during the period like as national trends. Prefectural chemical N and P applications for tea, orchard and forage remained unchanged in line with national trends. Manure N and P applications for each crop did not follow the trends for chemical fertilizer. Although chemical fertilizer application declined, N and P crop withdrawal for paddy rice, upland crops and tea increased as a result of optimizing fertilizer timing and placement. Nitrogen and P balance for each crop indicated a surplus; P surplus was larger than N surplus, because of higher P input and lower crop P withdrawal. Chemical N fertilizer determined N surplus except for forage, which was determined by manure application. Therefore N surplus on paddy rice, upland crops, orchard and tea declined and increased on vegetables. Forage recorded an N deficiency in two 5-year periods nationally because of low manure input. Because P balance was also determined by chemical P fertilizer, the P surplus for paddy rice and upland crops declined and the P surplus for vegetables increased during the period. Total P surplus was reduced on paddy rice and upland crops. Trends for chemical fertilizer, manure and N and P balance varied widely among prefectures, especially for P. Crop withdrawal of N and P varied relatively little. Although prefectural trends did not always follow the national trend, we could conclude that the negative environmental effects of Japanese crop production have diminished recently, and an improvement in N and P balance in vegetable production can be expected.

Appendix 1

See Fig. 6.

Fig. 6

Geographic location of prefectures referred to in the paper. Aichi: high vegetable yielding; Akita: lowest manure application and low N balance; Chiba: lowest chemical N fertilizer application for vegetables in 1985; Ehime: low crop yield for high area of orchard; Fukui: low manure application; Gunma: high vegetable yielding; Hokkaido: lowest chemical N fertilizer for vegetables, the lowest N balance; Ibaraki: high manure for vegetables, high vegetable yielding; Ishikawa: highest chemical P fertilizer in total and for vegetables in 2005; Iwate: lowest chemical P fertilizer in total in 1985 and 2005, and for vegetables in 2005, high manure application for vegetables; Kagawa: high N balance; Kagoshima: second highest manure application and livestock density, high manure application for vegetables; Kanagawa: high N balance; Kochi: highest chemical N fertilizer for vegetables, high vegetable yielding; Mie: high manure for vegetables; Miyazaki: highest manure application and highest livestock density, high manure for vegetables; Niigata: low N balance; Okinawa: highest crop yielding, highest chemical N fertilizer for upland crops in 2005; Osaka: second largest population prefecture; Saga: highest chemical N fertilizer for vegetables in 1985, low manure application; Shiga: low N balance; Shizuoka: highest chemical N fertilizer because of the large area of tea, highest N balance in 2005; Tokyo: largest population prefecture, lowest chemical N fertilizer for upland crops; Tottori: highest chemical P fertilizer in 1985; Toyama: low N balance; Wakayama: lowest crop yield for high area of orchard; Yamanashi: lowest chemical N fertilizer in 2005, low crop yield for high area of orchard