@article{oai:repository.naro.go.jp:00001213,
 author = {住田, 弘一 and SUMIDA, Hirokazu and 加藤, 直人 and KATO, Naoto and 西田, 瑞彦 and NISHIDA, Mizuhiko},
 journal = {東北農業研究センター研究報告, Bulletin of TOHOKU Agricultural Research Center},
 month = {Mar},
 note = {To promote paddy-upland (irrigated paddy rice and upland crop) rotation farming, sustainability of crop production in the successive rotation system should be investigated from a long term view. The changes in soil nitrogen fertility, soybean productivity, and paddy rice productivity were investigated by long-term field experiments in paddy-upland rotation in combination with different paddy/upland periods and organic material application in gray lowland soil in the cold-temperate region of Japan (NARCT, Omagari, Akita). When a paddy-upland rotation cultivating paddy rice and soybean in a cycle of 3-4 years upland and 1-2 years paddy (medium-term upland rotation) was continued for ten years or more, the available nitrogen in soil decreased greatly. Although the depletion of available soil nitrogen was mitigated by rice straw application at six tons per hectare in the case of short-term upland rotation (paddy-upland rotation in a cycle of 1-2 years upland and 1-3 years paddy), it was not mitigated by rice straw application in the medium-term upland rotation. Cultivating soybean for eighteen years on upland field converted from paddy field (long-term upland conversion) decreased available soil nitrogen more than the paddy-upland rotation did. The available soil nitrogen in the long-term upland conversion, even with application of rice straw compost of twenty tons per hectare, was markedly lower than that in the continuous paddy field without organic material application. In response to the depletion of available soil nitrogen, the yield of soybean on upland fields in the paddy-upland rotation and the long-term upland conversion decreased by ten to twenty percent compared with that in the field where soybean was planted after sufficient paddy period. On the other hand, the yields of paddy rice in the cases of both paddy-upland rotation and reconversion from the long-term upland conversion were higher than that in the continuous paddy field., 田畑輪換を繰り返しつつ, 持続的に作物を安定生産できるかどうかは, 水田輪作営農を推進していく上で政策的にも極めて重要な問題であり, 長期的視点から作物生産力を評価する必要がある。そこで, 有機質資材の投入管理を組み合わせた長期的な畑転換や田畑輪換を繰り返したほ場において, 土壌肥沃度や転作大豆及び復元田水稲の生産力の変化を調べた。寒冷地において, 水稲と大豆による田畑輪換を畑期間が過半を占める体系で10 年以上繰り返すと, 土壌の可給態窒素が大きく減耗する。この可給態窒素の減耗は, 畑期間が1 ～ 2 年の田畑輪換の場合には, 600 kg／10a の稲わらを毎年投入することにより軽減される。しかし, 畑期間が過半を占める場合には稲わら施用の効果がみられない。長期にわたり大豆を連作すると, 田畑輪換の場合より可給態窒素の減耗が激しく, 稲わら堆肥を2 トン／10a 連用しても, 連年水田の堆肥無施用の場合を大きく下回る。このような可給態窒素の減耗に伴って, 田畑輪換の繰り返しや長期畑転換における大豆の収量は, 十分な水田期間を確保した輪換畑に比べ10 ～ 20 %減収する。一方, 復元田の水稲は, 田畑輪換の繰り返しや長期畑転換を経ても, 連年水田に比べて増収する。},
 pages = {39--52},
 title = {田畑輪換の繰り返しや長期畑転換に伴う転作大豆の生産力低下と土壌肥沃度の変化},
 volume = {103},
 year = {2005},
 yomi = {スミダ, ヒロカズ and カトウ, ナオト and ニシダ, ミズヒコ}
}