持続可能な農業強化が窒素排出を削減しながら収穫量を維持 (‘Sustainable intensification’ on the farm reduces soil nitrate losses, maintains crop yields)

2025-03-14

2025-03-13 イリノイ大学アーバナ・シャンペーン校

イリノイ大学アーバナ・シャンペーン校の研究者らは、9年間にわたる研究で、従来のトウモロコシと大豆の2年輪作に比べ、トウモロコシ、ライムギ、大豆、冬小麦を含む3年輪作システムが、作物の収量を維持しながら、農地からの硝酸塩の流出を大幅に削減できることを明らかにしました。硝酸塩の流出は、地下排水パイプ（タイル）を通じて行われ、河川や湖沼の汚染、さらにメキシコ湾の低酸素「デッドゾーン」の拡大に寄与しています。この研究は、農業における持続可能な集約化が環境保全と生産性の両立に有効であることを示しています。

＜関連情報＞

トウモロコシ-ダイズ-冬小麦/ダイズの多様な輪作とトウモロコシの後の穀物ライ麦はタイル硝酸塩の損失を減らす
A diverse rotation of corn-soybean-winter wheat/double crop soybean with cereal rye after corn reduces tile nitrate loss

Lowell E. Gentry^,Corey A. Mitchell^,John M. Green^,Carlos Guacho^,Eric Miller^,Dan Schaefer^,Annette K. Vasquez^,Zhongjie Yu
Frontiers in Environmental Science Published:11 February 2025
DOI:https://doi.org/10.3389/fenvs.2025.1506113

Artificial drainage via subterranean drainage pipes called tiles transport nitrate from fields to streams, impairing downstream surface waters. Increased crop rotational diversity may conserve nitrogen, support greater system resiliency, and reduce tile nitrate loss. This 9-year study compares tile nitrate loss under a 3-year rotation of corn-soybean-winter wheat/double crop soybean plus cereal rye after corn versus a conventionally managed 2-year corn-soybean rotation. Tile flow and tile nitrate concentration were measured from 2015 through 2023 to determine annual flow weighted mean concentrations and loads of tile nitrate. Cereal rye following corn greatly reduced annual tile nitrate; however, more than 6 Mg ha⁻¹ of above ground biomass may have decreased soybean yield. Winter wheat was efficient at using split-applied fertilizer nitrogen (N) as annual tile nitrate concentrations were reduced similar to cereal rye. Double crop soybean after winter wheat may be the most productive phase of the rotation; however, an early killing freeze greatly reduced soybean yield and increased tile nitrate loss. Interestingly, the subsequent corn crop may have benefitted from this unexpected N source. Overall, tile nitrate loss was approximately 50% less in the diverse 3-year rotational system, suggesting that a more diverse rotational system is efficient at retaining N, conserving nitrogen in the field, and reducing N loss to surface water. This study demonstrated proof of concept that a more diverse crop rotation can reduce tile nitrate loss from fields to streams, while maintaining crop productivity.