Atmospheric CO₂ Enrichment and Reactive Nitrogen Inputs Interactively Stimulate Soil Cation Losses and Acidification

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Rising atmospheric CO2 (eCO2) and reactive nitrogen (Nr) inputs can affect plant growth and soil nutrient dynamics.
• Acidic tropical and subtropical croplands are particularly vulnerable to changes in soil chemistry due to low organic matter and nutrient cations.
• The interactive effects of eCO2 and Nr on soil cation nutrients and acidity remain under-examined.

Purpose of the Study:

• To investigate the dynamics of soil cation nutrients and acidity under elevated CO2 and different nitrogen sources in a subtropical agricultural soil.
• To understand how eCO2 and Nr interact to influence soil chemistry and nutrient availability.
• To assess the implications for plant growth and nutrient limitations in vulnerable ecosystems.

Main Methods:

• Experimental investigation of cation dynamics in a plant-soil system.
• Exposure to elevated atmospheric CO2 (eCO2) and various nitrogen (N) sources.
• Analysis of soil solutions and leachates in aerobic agroecosystems.

Main Results:

• Both eCO2 and Nr, individually and interactively, increased calcium (Ca2+) and magnesium (Mg2+) in soil solutions.
• eCO2 significantly reduced soil pH, an effect amplified by ammonium (NH4+-N) inputs.
• This study provides the first direct evidence of eCO2 enhancing soil acidity, linked to plant preferences and growth.

Conclusions:

• eCO2 and Nr significantly alter soil cation dynamics and increase soil acidity in subtropical agricultural soils.
• Plant responses to eCO2, particularly NH4+-N preference, contribute to soil acidification.
• Findings highlight the need for further research on plant-soil responses to climate change in acidic tropical and subtropical regions.