22-years long-term fertilizations increase soil organic carbon and alter its chemical composition in three wheat/maize cropping sites across central to south China

Professor Minggang Xu1,2, Ms Yating He2,3, Ms Wenju Zhang2, Mr Xueyun Yang4, Ms Shaomin Huang5, Mr Xinhua He6

1Institute of South Asia Tropical Crops, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang, China, 2Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Haidian, China, 3Research Institute of Forestry Policy and Information, Chinese Academy of Forestry, Haidian, China, 4State Key Laboratory of Soil Erosion and Dryland Farming, Northwest A & F University, Yangling, China, 5Institute of Plant Nutrition, Resources and Environment, Henan Academy of Agricultural Sciences, Zhengzhou, China, 6College of Resources & Environment, Southwest Univ/Univ of Western Australia, Beibei, China

As a quantifiable component of soil organic matter, soil organic carbon (SOC) is at the core of soil fertility and the C sequestration in SOC is a pathway to mitigate climate change by reducing atmospheric CO2. Studies have shown that fertilization strategies can alter SOC sequestrations and stocks, but information about fertilization effects on SOC chemical composition is limited. Using the solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy, we examined changes in the SOC chemical composition of three soils (0–20 cm depth) from an annual maize/wheat double-cropping system across central to south China. These soils had been subjected to 22-years (1990–2012) long-term fertilization. Compared with unfertilized control, SOC stocks were significantly increased under chemical nitrogen, phosphorus and potassium fertilization (NPK), NPK plus straw (wheat straw, NPKS), and NPK plus manure (varied horse, pig and cattle manure, NPKM). The O-alkyl C (labile C), not the alkyl C (persistent C), was consistently increased across the three fertilized treatments. Additionally, all fertilized treatments decreased the ratio of alkyl-C/O-alkyl-C (SOC decomposition index) or aliphatic-C/aromatic-C (SOC complexity index), indicating that the SOC decomposition was delayed, or SOC was converted into a more complicated structure. The soil C of NMR-determined functional groups (alkyl C, O-alkyl C, aromatic C, and carbonyl C) was positively correlated with the cumulative C input (P < 0.05). The conversion rate of functional groups was highest in O-alkyl C, indicating a largest contribution to the increase of SOC accumulation. Soil pH, C/N ratio and clay were the major factors affecting the functional-group conversion rates, whereas annual precipitation, temperature, and accumulated temperature (>10 °C) played little roles. In conclusion, these results can be applied to the improvement of agricultural soil C sequestration or restoration capacity through changing SOC chemical structure under long-term fertilizer managements.


Xinhua He is currently a Professor and Director of Centre of Excellence for Soil Biology at Southwest University, Chongqing China (2015-). He has held a PhD in Plant Ecophysiology from University of Queensland, Australia since 2002, and then worked as a Postdoctoral Fellow at UC Davis and University of Tokyo, Senior Research Scientist at USDA and University of Western Australia.

During the past 20 years, Xinhua has focused on carbon/nitrogen movement in agricultural and natural ecosystems, roles of soil beneficial microbes in plant ecophysiology and soil structural stability and health, nano-minerals complexation in the preservation of soil organic matter under contrasting fertilizations. Xinhua is currently exploring emerging technologies including stable isotopes of 13C and 15N, Pyrosequencing, Electron Microscopy, Nano-scale Secondary Ion Mass Spectrometry (nano-SIMS), and Synchrotron Radiation Facility, etc., to address above-mentioned topics in a variety of plant-microbial-soil systems under global environmental change scenarios.

Currently Xinhua has >200 publications including 3 books, 26 book chapters and >170 papers in a variety of journal including Agri Ecosyst Environ, Biol Fert Soils, Biogeosciences, Glob Biogeochem Cy, Nature Commu, Nature Geosci, New Phytologist, Plant Soil, SBB, Trends Ecol & Evol, Trends Plant Sci, Tree Physiol, etc. (see https://www.researchgate.net/profile/Xinhua_He3). At present Xinhua has presented >100 talks at various universities and international conferences and his research has been viewed by 70,000 times by >4,000 readers from the Mendeley data base. Xinhua has been servicing as a Section Editor for Plant and Soil (2015) and an Associate Editor Soil Research (2019) and a regular peer reviewer for >100 journals and funding bodies (ARC, GRDC, BBSRC sLOLA, NSF, NSFC, USDA and NOW) around the world.

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