Preventing subsoil enhanced nitrification to safeguard agroecosystem sustainability

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Science

Background:

• Excessive nitrogen fertilizer application leads to significant nitrogen losses.
• Soil degradation and groundwater nitrate pollution are major environmental concerns linked to agriculture.

Purpose of the Study:

• To identify and characterize a previously overlooked subsurface layer responsible for enhanced nitrification.
• To understand the key processes driving the formation and function of this layer.
• To propose new targets for nitrogen management in croplands.

Main Methods:

• Synthesis of global nitrogen profiles.
• Analysis of field studies on nitrogen cycling in croplands.
• Identification of the enhanced nitrification layer (ENL) at approximately 0.6m depth.

Main Results:

• A distinct enhanced nitrification layer (ENL) was identified globally in croplands at 0.3–0.9m depth.
• ENL formation is driven by root nitrogen transport, oxygenated microenvironments, nitrifier communities, and hydrology.
• The ENL acts as a biogeochemical hotspot, causing subsoil pH decline and nitrate leaching.

Conclusions:

• The ENL is a critical subsurface target for improving nitrogen management.
• Integrating ENL management with surface strategies enhances agroecosystem sustainability.
• Addressing this deep soil layer is crucial for mitigating nitrogen pollution and soil degradation.