Effect of Nutrient Management on δ15N, δ13C Isotopes and Enzyme Activities in Higher Altitude Agricultural Soils, India

Abstract

This research under field experimental conditions was conducted to evaluate the effects of nutrient management on δ15N, δ13C isotopes and soil enzyme activities in higher altitude agricultural soils. Three composite soil samples were collected from each of the organic management (ORG), inorganic management (IM) and control (CON) experimental plots from the fall of September 2017 to August 2018. δ15N was significantly higher (8.95‰) in ORG soils compared than IM (8.07‰) and CON (6.36‰). In contrast δ13C was higher (-16.49‰) in CON soils compared to IM (-19.26‰) and ORG (-19.8‰). 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 and CON. Urease, β – glucosidase, acid phosphatase, alkaline phosphatase, invertase, cellulase and dehydrogenase activities were 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 δ15N and δ13C isotopes are good indicators to monitor the soil health and C and N biogeochemical cycles in higher altitude agricultural soils.