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RESEARCH ARTICLE

Impact of continuous organic manuring on mechanisms and processes of the stabilisation of soil organic C under rice–wheat cropping system

T. J. Purakayastha https://orcid.org/0000-0002-8669-3842 A D , Ruma Das A , Savita Kumari A , Y. S. Shivay B , Sunanda Biswas A , Dhiraj Kumar A and Bidisha Chakrabarti C
+ Author Affiliations
- Author Affiliations

A Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi 110012, India.

B Division of Agronomy, Indian Agricultural Research Institute, New Delhi 110012, India.

C Center for Environment Science and Climate Resilient Agriculture, New Delhi 110012, India.

D Corresponding author. Email: tpurakayastha@gmail.com

Soil Research 58(1) 73-83 https://doi.org/10.1071/SR19014
Submitted: 22 January 2019  Accepted: 12 September 2019   Published: 22 October 2019

Abstract

Understanding the mechanism of soil organic carbon (SOC) stabilisation may help in developing management strategies for SOC storage. A long-term organically managed rice−wheat cropping system was used for SOC stabilisation study. Soil samples were collected from control, FYM (farmyard manure to rice and wheat), GM (green manure; Sesbania aculeata to rice and Leucaena leucocephala to wheat), GB (GM with biofertiliser; blue green algae to rice and Azotobacter sp. to wheat), GF (GM with FYM), GFB (GM with FYM and biofertiliser). Sodium hypochlorite (NaOCl)-resistant C correlated significantly with ammonium oxalate and dithionate extractable Fe, Al and Si in soil. The GFB showed the highest enrichment of SOC (32%) as well as NaOCl-resistant C (22%) at 0–15 cm soil depth. At higher soil depth, GM alone showed the highest enrichment of SOC (39% at 15–30 cm, 84% at 30–60 cm). The NaOCl-resistant C was higher in FYM and GFB treatments at 15–30 and 30–60 cm depths respectively. The proportion of NaOCl-resistant C to SOC increased down the profile and was highest (30–52%) in 30–60 cm soil depth. A multiple regression model developed between ammonium oxalate extractable Fe, Al and Si and SOC could well predict the stable SOC content. There was a substantial improvement in prediction when extractable Fe, Al and Si were combined together. Among the organic treatments, GFB showed the highest humification and aromaticity in humic acid with least polarity and more reduced form. The combination of all the organic sources (GFB) could be a promising nutrient management strategy for enhancing the stability of SOC in rice–wheat cropping systems of semiarid subtropical India.

Additional keywords: Al and Si, amorphous Fe, humic acid, NaOCl-resistant C.


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