Optimization of crop residue management practice to improve soil aggregation and mineral-associated organic carbon in a clay soil of Bangladesh

• The study was conducted in subtropical soil under short-term rice-mustard cropping system. • Straw return and straw + NPK increased the soil aggregation improving SOC. • SB reduces the aggregation and soil organic carbon content. • Straw + NPK enhanced AAOC and MAOC than other straw return strategies. Organic matter application is considered an important option to increase soil aggregate formation and mineral-associated organic carbon (MAOC) in soil. In south Asia, different conventional strategies of soil management are used to improve soil quality. However, among these strategies the sustainable soil management option and the driver to enhance soil aggregation and MAOC still remain largely elusive. The objective of the present investigation was to optimize the sustainable soil management strategy for aggregation and MAOC stabilization. A short-term field study was conducted under widely used six crop residue management approach. These are: 1. Control, 2. Synthetic fertilization (NPK), 3. Straw, 4. Straw + NPK, 5. Straw burning (SB), 6. NPK + SB. Results exhibited that the highest aggregation was found in straw followed by straw + NPK. Moreover, straw and straw with fertilization increased SOC by 48 % and 32 %, respectively, compared to the control, while SB reduced soil aggregation and SOC (P < 0.05). The highest MAOC in small macroaggregates and microaggregates was found in residue with supplementary nutrients addition treatments. Soil aggregation enhancement was contributed by SOC, while mineral- and aggregate-associated SOC increment was contributed by fungal activity (P < 0.05). The findings show that only straw return increase the aggregation and SOC, while the integrated application of organic matter with synthetic fertilizers increases aggregation and MAOC triggering fungal activity to mitigate atmospheric carbon emissions in the subtropical clay soil.