Assessment of Carbon Pools and Stocks in an Inceptisol Under Long-Term Manuring and Fertilization in Rice-Wheat Cropping System: Comparison of Different Methods

ABSTRACT

The objective of the study was to assess the 32 years impact of long-term manuring and fertilization on soil organic C (SOC) pools and stocks under rice-wheat cropping system in an Inceptisol and compare different methods for estimation of labile and resistant SOC pools. The treatments included control (T1), 100% NPK- fertilizer (T2), 50% NPK + 50% N-FYM (T3), 75% NPK + 25% N-FYM (T4), 50% NPK + 50% N-wheat straw (WS) (T5), 75% NPK + 25% N-WS (T6), 50% NPK + 50% N-green manure (GM) (T7), and 75% NPK + 25% N-GM (T8). The soil samples were analyzed for SOC, oxidizable and resistant C by hot water (HWEC, HWRC), KMnO₄ (KMnO₄-Cox, KMnO₄-Cres), NaOCl (NaOClox, NaOCl-Cres), bulk density. As compared to 100% NPK, the SOC stocks (0–60 cm) in T3, T5, and T7 were increased by 10, 9.3, and 5.6%, respectively. The mean NaOCl-Cox, C mineralization (Cmin), HWEC, and KMnO₄-Cox stocks contributed 37, 11, 6, and 4% of SOC stock. The correlation study showed that Cmin positively correlated with KMnO₄-Cox, HWEC, and NaOClox. For assessing the mineralizable SOC pool, NaOCl-Cox overestimated, while HWEC and KMnO₄-Cox underestimated it. Thus, these protocols need to be modified to match the Cmin data. However, NaOClox is recommended for assessing mineralizable SOC over 90 days of incubation.

KEYWORDS:

• FYM
• green manure
• rice-wheat cropping system
• SOC pools
• SOC stock

Acknowledgements

We sincerely acknowledge the Indian Council of Agricultural Research and Indian Agricultural Research Institute, New Delhi for financial support (Grant No. 10534) and ICAR-AICRP on Integrated Farming System (IFS) Kanpur Centre, Uttar Pradesh for assisting in conducting this research.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data is available on request from the authors. The data supporting the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

The work was supported by the ICAR-Indian Agricultural Statistics Research Institute [Grant No. 10534].