Mechanisms underlying episodic nitrate and phosphorus leaching from poorly drained agricultural soils.

Poorly drained depressions within tile-drained croplands can have disproportionate environmental and agronomic impacts, but mechanisms controlling nutrient leaching remain poorly understood. We monitored nitrate and soluble reactive phosphorus (SRP) leaching using zero-tension soil lysimeters across a depression to upland gradient over 2 years in a corn-soybean (Zea mays L.-Glycine max [L.

Poorly drained depressions can be hotspots of nutrient leaching from agricultural soils.

Much of the US Corn Belt has been drained with subsurface tile to improve crop production, yet poorly drained depressions often still flood intermittently, suppressing crop growth. Impacts of depressions on field-scale nutrient leaching are unclear. Poor drainage might promote denitrification and physicochemical retention of phosphorus (P), but ample availability of water and nutrients might exacerbate nutrient leaching from cropped depressions.

Nitrous oxide emissions from agricultural soils challenge climate sustainability in the US Corn Belt.

Agricultural landscapes are the largest source of anthropogenic nitrous oxide (NO) emissions, but their specific sources and magnitudes remain contested. In the US Corn Belt, a globally important NO source, in-field soil emissions were reportedly too small to account for NO measured in the regional atmosphere, and disproportionately high NO emissions from intermittent streams have been invoked to explain the discrepancy. We collected 3 y of high-frequency (4-h) measurements across a topographic gradient, including a very poorly drained (intermittently flooded) depression and adjacent upland soils.