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

Abstract

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.