Zhang Jiuming, Wang Jingkuan, An Tingting, Wei Dan, Chi Fengqin, Zhou Baoku
College of Land and Environment, Shenyang Agricultural University, Shenyang, China.
Soil Fertilizer and Environment Resources Institute, Heilongjiang Academy of Agricultural Sciences, Key Laboratory of Soil Environment and Plant Nutrition of Harbin, Heilongjiang Province, China.
PLoS One. 2017 Nov 2;12(11):e0186918. doi: 10.1371/journal.pone.0186918. eCollection 2017.
The composition and structure of humic acid (HA) can be affected by fertilization, but the short-term effects are difficult to detect using traditional analysis methods. Using a 35-year long-term experiment in Black Soil, the molecular structure of HA was analyzed with Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance spectroscopy (NMR), and fluorescence spectroscopy. Variation in HA was analyzed after long-term fertilization, including fertilization with manure (M), inorganic N, P and K fertilizer (NPK), manure combined with inorganic N, P, and K fertilizer (MNPK), and a no-fertilizer control (CK). The application of each fertilizer treatment increased crop yields compared with the CK treatment, and the MNPK treatment increased crop yield the most. The ratio of main IR absorption peak of HA at 2,920 cm-1 compared with the peak at 2,850 cm-1 (2920/2850) was higher in the NPK and MNPK treatments compared with the CK treatment. The application of manure (MNPK and M treatments) increased the ratio of hydrogen to carbon (H/C) in HA, and raised the ratio of the main IR absorption peak of HA at 2920 cm-1 to that at 1720 cm-1 (2920/1720). Manure treatments also raised the ratio of aliphatic carbon (C) to aromatic C, alkyl C to alkoxy C and hydrophobic C to hydrophilic C and the fluorescence index (f 450/500), but decreased the degree of aromatization of HA, when compared with the CK treatment. The ratio between each type of C in HA was similar among all the fertilizer treatments, but NPK had a lower ratio of H/C and a lower content of aliphatic C compared with the CK treatment. These results indicated that the molecular structure of HA in Black Soil tends to be aliphatic, simpler, and younger after the application of manure. While the application of inorganic fertilizers increased in the degree of condensation of HA and made HA structure complicated. The application of manure alone or combined with inorganic fertilizers may be an effective way to increase crop yield and improve the structure of soil organic matter.
腐殖酸（HA）的组成和结构会受到施肥的影响，但使用传统分析方法难以检测到短期影响。通过在黑土上进行的为期35年的长期试验，利用傅里叶变换红外光谱（FTIR）、13C核磁共振光谱（NMR）和荧光光谱对HA的分子结构进行了分析。分析了长期施肥后HA的变化情况，包括施用有机肥（M）、无机氮磷钾肥（NPK）、有机肥与无机氮磷钾肥配施（MNPK）以及不施肥对照（CK）。与CK处理相比，各施肥处理均提高了作物产量，其中MNPK处理增产最多。与CK处理相比，NPK和MNPK处理中HA在2920 cm-1处的主要红外吸收峰与2850 cm-1处的峰的比值（2920/2850）更高。施用有机肥（MNPK和M处理）提高了HA中氢碳比（H/C），并提高了HA在2920 cm-1处的主要红外吸收峰与1720 cm-1处的峰的比值（2920/1720）。与CK处理相比，有机肥处理还提高了脂肪族碳（C）与芳香族碳、烷基碳与烷氧基碳、疏水碳与亲水碳的比值以及荧光指数（f450/500），但降低了HA的芳构化程度。所有施肥处理中HA中各类碳之间的比例相似，但与CK处理相比，NPK处理的H/C比值较低，脂肪族碳含量较低。这些结果表明，施用有机肥后黑土中HA的分子结构趋于脂肪族化、更简单且更年轻。而施用无机肥料增加了HA的缩合程度，使HA结构复杂化。单独施用有机肥或与无机肥料配施可能是提高作物产量和改善土壤有机质结构的有效途径。
