Soil aggregate variation in two contrasting rice straw recycling systems for paddy soil amendment over two years

ABSTRACT

Soil aggregate is important to soil quality. Straw return is beneficial for soil amendment, but the effects of straw and straw-derived biochar on aggregate formation and stability in paddy soil are unclear. This study carried out a field experiment for 2 years in Northeast China with four treatments: conventional fertilization (CF), straw (ST, 7.5 t ha⁻¹ year⁻¹), biochar (BC, 2.5 t ha⁻¹ year⁻¹), and biochar-based fertilizer (BCF, 0.75 t ha⁻¹ year⁻¹). Compared with the CF and BCF, BC and ST improved the macroaggregates and significantly increased soil total carbon and aggregate organic carbon, indicating a sustained positive role in promoting the formation and stability of aggregates. BC significantly improved aggregate stability. Correlation analysis showed that macroaggregates (2–0.25 mm) can be increased by increasing the heavy fraction organic carbon (HFOC), BC and ST significantly increased the HFOC, and BC had a greater effect. Scanning electron microscopy (SEM) showed that the combination of biochar and soil particles can be captured with strong water scouring. BCF showed an increasing trend in the formation and stability of soil aggregates. In comparison, biochar had a greater effect on promoting the formation of macroaggregates and the stability of soil aggregates with a significant sustainable effect.

KEYWORDS:

• Soil aggregate
• biochar
• straw
• paddy soil
• organic carbon

Acknowledgments

Authors thank Zifan Liu, Wenjia Wang and Yuxue Zhang for their help in the experiment.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA28090300), the State Key Special Program of Biochar-based Fertilizer Development and Application Technology for Soil Fertility Improvement in Rice (2016YFD0300904-4), the Special Fund for Academicians, and Earmarked Fund for Modern Agroindustry Technology Research System (CARS-01-51).