Nitrogen Flow in Agropastoral Systems, Brazil

JIRCAS Journal
ISSN 13407686
書誌レコードID(総合目録DB) AA11030483

Agropastoral systems that combine soybean and grasses in a crop rotation have been proposed for sustaining grassland productivity in the low-fertility soils of the Brazilian savanna. We studied the nitrogen flow under an agro-pastoral system developed in 1993 in a Purple Red Latosol in Campo Grande, MS. Four cropping systems were included: continuous soybean cropping, soybean cropping after 4 years of grass cultivation, continuous grass cultivation, grass cultivation after 4 years of soybean cropping. The rate of N fixation in soybean was determined by the N difference method and 15N natural abundance method. A non-nodulating isoline, T201, was used as a control in both methods. The rate of N2 fixation ranged from 23 to 51 % of the total plant N. The amount of N taken out as grains was larger than the amount of fixed N in soybean. The amount of N entering the system through rainwater was 6 kgN/ha/yr. Nitrate accumulating in soil from the surface to a depth of 100 cm under soybeans indicated the potential leaching of nitrate. The estimated amount of nitrate leaching from the soybean fields was large compared with that from the grasslands. A large negative N balance of 134-211 kgN/ha/yr was estimated in the soybean fields, whereas the N balance in the grasslands was a slightly negative.

作成者 Kenichi KANDA Motoki TAKAHASHI Cesar H.B. MIRANDA
著者キーワード leaching nitrogen fixation soybean grassland nitrogen balance
公開者 Japan International Research Center for Agricultural Sciences
国立情報学研究所メタデータ主題語彙集(資源タイプ) Journal Article
開始ページ 23
終了ページ 31
権利 Japan International Research Center for Agricultural Sciences
言語 eng