Stable Isotope (δ¹³C and δ¹⁵N) Signatures and Their Relationship among Soil Enzyme Activities in Indian Semi-arid Agricultural Soils

ABSTRACT

A field evaluation of the stable isotopes (δ¹³C and δ¹⁵N) and their relationship among physicochemical and enzyme activities was conducted in Indian semi-arid agricultural soils. Composite soil samples were collected based on organic management (ORG), inorganic management (IM), integrated crop management (ICM) and precision farming (PF) experimental plots from the fall of September 2017 to October 2018. δ¹⁵N was significantly higher (13.85 %) in ORG soils compared with ICM (13.28 %), IM (12.84 %) and PF (12.75 %). In contrast δ¹³C was higher (−13.25%) in PF soils than IM (−13.6 %), ICM (−15.07 %) and ORG (−15.23 %). Soils from ORG had significantly higher levels of total N, total C, total S, organic carbon, available N, extractable P, Soil organic carbon stock, exchangeable K and enzyme activities compared to IM, ICM and PF. Urease, β – glucosidase, acid phosphatase, alkaline phosphatase, invertase, cellulase and dehydrogenase activities significantly increased the δ¹⁵N and reduced δ¹³C in agricultural soils. Our results suggested that organic management had improved the δ¹⁵N, plant available nutrients and soil enzyme activities. Stable δ¹³C and δ¹⁵N isotopes are good indicators of monitor the soil health, carbon, and nitrogen biogeochemical cycles in Indian semi-arid agricultural soils.

KEYWORDS:

• Stable isotopes
• organic management
• soil organic carbon
• soil enzymes and biogeochemical cycle

Acknowledgments

The authors are grateful towards the Department of Environmental Sciences, Tamil Nadu Agricultural University for providing laboratory facilities in order to conduct the experiment. They extend their gratitude to Sustainable Organic Agriculture (T.N.A.U) and Precision Farming Development Center (T.N.A.U) for conducting field experiments. We also record our sincere thanks to ACMS Laboratory, IIT Kanpur, India for stable isotopes analysis.

Disclosure statement

The authors declare that they have no conflict of interest.

Additional information

Funding

The present research was funded through an N-PDF project ID.No. PDF/2016/003496, funded by DST-SERB, Government of India.