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

This research under field experimental conditions was conducted to evaluate the effects of nutrient management on delta N-15, delta C-13 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. delta N-15 was significantly higher (8.95 parts per thousand) in ORG soils compared than IM (8.07 parts per thousand) and CON (6.36 parts per thousand). In contrast delta C-13 was higher (-16.49 parts per thousand) in CON soils compared to IM (-19.26 parts per thousand) and ORG (-19.8 parts per thousand). 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, beta - glucosidase, acid phosphatase, alkaline phosphatase, invertase, cellulase and dehydrogenase activities were significantly increased the delta N-15 and reduced delta C-13 in agricultural soils. Our results suggested that organic management had improved the delta N-15, plant available nutrients and soil enzyme activities. Stable delta N-15 and delta C-13 isotopes are good indicators to monitor the soil health and C and N biogeochemical cycles in higher altitude agricultural soils.

Automated summary

The research found that organic management improved soil organic carbon content, nutrient levels, and enzyme activities, enhancing soil quality by increasing delta N-15 and decreasing delta C-13. Stable delta N-15 and delta C-13 isotopes serve as good indicators for monitoring soil health and carbon-nitrogen biogeochemical cycles in higher altitude agricultural soils.