Cereal-legume intercropping stimulates straw decomposition and promotes soil organic carbon stability

Area of Science:

• Agricultural Science
• Soil Science
• Climate Change Mitigation

Background:

• Increasing soil carbon sequestration is vital for climate neutrality.
• The impact of legume-based crop diversification on soil organic carbon (SOC) fractions in drylands remains unclear.
• Understanding the transformation of particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) is crucial.

Purpose of the Study:

• To investigate how legume-based crop diversification affects SOC fractions, specifically POC and MAOC, in dryland agroecosystems.
• To determine the fate of photosynthesized carbon and straw residue decomposition under different cropping systems.
• To assess the role of intercropping with cover crops in enhancing soil carbon stability.

Main Methods:

• Utilized an in situ 13C labeling technique to trace carbon fate.
• Compared soybean-wheat and soybean-maize intercropping systems with their respective monocultures.
• Included treatments with and without cover crops over a 4-year period.

Main Results:

• Intercropping significantly increased mineral-associated organic carbon (MAOC) by 5.6%.
• More photosynthesized carbon was transferred to MAOC, with less retained in the POC fraction.
• Intercropping enhanced soil nitrogen content and reduced C/N ratios, alleviating microbial nitrogen limitation and accelerating residue decomposition.

Conclusions:

• Legume-based crop diversification effectively enriches soil nitrogen and promotes the transformation of POC to MAOC.
• This transformation enhances the persistence of soil organic carbon (SOC), contributing to the SOC pool.
• The findings suggest a viable strategy for achieving carbon neutrality in dryland agroecosystems under climate change.