Five years of biochar amendment combined with reduced fertilization and irrigation improved the soil organic carbon composition and structure in a solonchak

Summary

This five-year field study in saline-alkali soil demonstrates that biochar amendment combined with low nitrogen input and reduced irrigation (LNLWB) achieved the greatest increases in soil organic carbon (+61%) and light fraction organic carbon (+322%), whilst simultaneously increasing maize yield by 16%. Biochar enhanced SOC stability through increased aromatic and humic properties and improved soil porosity, with comprehensive principal component analysis scores substantially higher for biochar-amended treatments (0.57–0.74) than untreated controls (−0.56 to −0.49). The findings suggest that biochar represents an effective strategy for saline-alkali soils, potentially enabling two-thirds reduction in nitrogen fertiliser input whilst maintaining or improving productivity.

UK applicability

The study's focus on saline-alkali soils of the type found in northern China has limited direct applicability to UK agricultural conditions, where soil salinity is not typically a primary constraint. However, the mechanisms by which biochar improves soil organic matter stability and porosity may be relevant to UK soils, and the principle of reducing fertiliser inputs through soil amendment warrants investigation in UK contexts.

Key measures

Soil organic carbon (+61%), mineral-associated organic carbon (+54%), light fraction organic carbon (+322%), heavy fraction organic carbon (+3.5%), alkyl carbon/alkoxyl carbon ratio (+40%), maize yield (+16%), dissolved organic carbon (−37%), pore probability entropy (−0.8%), fractal dimension (−6%), principal component analysis scores for SOC content and structure

Outcomes reported

The study measured soil organic carbon (SOC) composition and structure, including mineral-associated and light fraction organic carbon, as well as maize yield, across multiple fertilisation and irrigation regimes with and without biochar over five years in a solonchak soil.

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