Impact of long-term nutrient supply options on aggregate associated total soil organic carbon concentration after nineteen years of rice-wheat cropping system

Nowadays, mitigating climate change through carbon management has received increased attention. While storage of total soil organic carbon within the soil aggregate size, aggregate associated carbon in relation to aggregate stability significantly varies among nutrient management practices. Using a 19-year long-term field experiment with four replicate plots of seven fertilisation practices [(T1: Control i.e. no chemical fertiliser or organic manure; T2: Recommended dose of fertiliser (RFD) to rice and wheat; T3: Soil-test based fertiliser application to both crops (STCR); T4; 75% of recommended fertiliser + 25% N as FYM in rice and full RFD in wheat (IPNS); T4: Fertiliser similar to T3, but substitution of every third wheat crop with berseem (IPNS + B); T6: Fertiliser similar to T3, but substitution of every third rice crop with forage cowpea (IPNS + C); T7: Organic farming (OF)], we investigated the aggregate associated carbon and relationship between different aggregate fractions under rice-wheat cropping system. OF, IPNS + C and IPNS + B significantly improved aggregate-associated soil organic carbon (TOC). It was more abundant in macroaggregates (+12%) than microaggregates. OF practices had significant superiority over all nutrient management practices in all size of aggregate. Results showed that in all four-soil aggregate size class (>2,000 µ m; 250-2,000 µ m; 53–250 µ m; and < 53 µ m) in both soil layer after competing 19 cropping system cycles of rice-wheat system. Strategies aiming to improve carbon storage within the aggregate size by adopting improve nutrient management practices.