• ISSN 1008-505X
  • CN 11-3996/S
LONG Jie-qi, MIAO Shu-jie, LI Na, HAO Xiang-xiang, QIAO Yun-fa. Effects of biochar application on the structural properties of organic matter fractions in Mollisols[J]. Journal of Plant Nutrition and Fertilizers, 2022, 28(5): 775-785. DOI: 10.11674/zwyf.2021290
Citation: LONG Jie-qi, MIAO Shu-jie, LI Na, HAO Xiang-xiang, QIAO Yun-fa. Effects of biochar application on the structural properties of organic matter fractions in Mollisols[J]. Journal of Plant Nutrition and Fertilizers, 2022, 28(5): 775-785. DOI: 10.11674/zwyf.2021290

Effects of biochar application on the structural properties of organic matter fractions in Mollisols

  • Objectives Biochar application has become one of the important agronomic strategies for increasing soil fertility. We studied the distribution of organic matter in various soil aggregates, and the variation of chemical structures of organic matter across density fractions, to understand the effect of biochar application on carbon sequestration potential of farmland soil.
    Methods The long-term experiment of biochar application was located in the Hailun Agricultural Ecological Experimental Station of the Chinese Academy of Sciences, which started from 2011. Soil samples were collected from the plots of applying biochar (+BC) and without biochar (−BC). Total conent of soil organic carbon was analyzed with conventional method. Subsamples were divided into four aggregate classes as > 2 mm, 2–0.25 mm, 0.25–0.053 mm and < 0.053 mm and soil organic carbon were determined in them. Moreover, subsamples were divided into free light fraction (LF), occluded light fraction (OF) and mineral-associated fraction (MF) according to their density. The concentration and characteristics of infrared spectrum of soil organic carbon in aggregates and density fraction were determined by Fourier infrared spectroscopy.
    Results Compared to –BC treatment, +BC treatment increased the concent of soil organic matter (SOM) in bulk soil, free light fraction (LF) and occluded light fraction (OF) by 19.72%, 73.50%, and 192.66%, respectively. +BC treatment increased the concent of SOM by 12.54% and 21.35% in >2 mm and 2–0.25 mm aggregates, respectively. Among the main functional groups in bulk soil, +BC treatment decreased the relative abundances of aromatic C=C and carbonyl C=O by 18.18% and 21.95%, respectively, while increased other groups, and the ratio of −CH/C=C and −CH/C=O increased by 66.67% and 62.11% respectively. In >2 mm aggregate, +BC treatment increased the relative abundance of aliphatic −CH by 55.11%, but decreased the aromatic C=C by 17.06%, leading to the increase in −CH/C=C and −CH/C=O ratios. In <0.25 mm aggregate, +BC treatment increased the relative abundance of aromatic C=C by 27.63%−49.83%, but reduced the aliphatic −CH by 16.58%−20.80%, leading to the decrease in −CH/C=C and −CH/C=O ratios. Compared to −BC treatment, +BC treatment increased the relative abundances of aliphatic —CH and aromatic −C=C in the three density fractions, and increased the —CH/C=C ratio in OF by 74.19%.
    Conclusions Biochar application increased significantly organic matter content in Mollisols, which led to more aliphatic groups in macro-aggregates and improved stability of micro-aggregates. The increment of relative abundance of aliphatic —CH in occluded fraction was the highest across density fractions, which enhanced the turnover of soil organic matter.
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