We collected samples from Lishu County Siping City Jilin Province, and conducted the positioning of the organic fertilizer experiment for three years. The soil was black , taken the topsoil (0~20 cm) for experimental analysis. There were 5 kinds of treatments in this experiment: applying chemical fertilizer(CK), cow dung combined with chemical fertilizer(A), hen dung combined with chemical fertilizer(B), corn stalk combined with chemical fertilizer(C) and leaves combined with chemical fertilizer(D). Among them, the content of chemical fertilizer was consistent, with other organic materials referred to the carbon contents. Each treatment repeated three times, with 15 plots in total. Five soil samples were collected in each plot, accorching to the “ S” sype sampling method, then mixed topether for are smaple.

The extraction method of POC was wet screening^{[8, 9]}: weighed 30 g air-dried soil samples which be sieved in the diameter of 2 mm, then putted them into 250 mL triangular flask, with 200 mL 0.5 g· L^-1 (NaPO₃)₆ added, and oscillated 16 hours. Soil suspension was sieved in the diameter of 0.053 mm. Repeated washing with distilled water, and soil granular component was left on the sieve, at 60 ℃ oven dried to constant weight. Then grinded and sieved in 0.149 mm for standby application.

Used American NICOLET infrared spectrometer to analysis the Infrared Spectroscopy, and scan mode was 4 000~400 cm^-1. POC samples were grinded less than 2 μ m with agate mortar, mixed KBr in proportion of 1∶ 100, and then grinded together. Finally 0.5~2 mg composite samples, tabletted, and scanned.

For ¹³C nuclear magnetic resonance (NMR) analysis, used superconductivity nuclear magnetic resonance spectrum AVANCE 400 WB(EX18-0011)to measure. ¹³ C-cross-polarization magic Angle spinning technology, Spectral frequency was 75.5 MHz, the rotor diameter was 4 mm, and Rotating frequency was 14 kHz^{[8, 10]}, accumulated 16 000 times.

¹³C NMR spectrogram are shown in Fig.1, mainly attribution of chemical shift to see table 1. By the Fig.1 shows, POC is mainly composed of aliphatic and aromatic carbon. Especially the content of aliphatic carbon is more than 75%(Table 1). Similar to other scholars’ spectra^[8]. The order of aromaticity is D> C> A> CK> B, aromaticity of D is significantly higher than other treatments, at least higher 3.5%. The aromaticity of B was slightly lower than CK; the difference was only 0.06%. The oxygen-containing functional groups of POC are more than 50%, declaring that POC has certain hydrophilicity and unstable structure. The order of oxygen-containing functional group is D> CK> A> C> B, and an average of more than 50%, D or CK has exceeded 60% (Table 1), which states that POC is mainly composed by oxygen aliphatic carbon, POC of D or CK has stronger hydrophilic. Because of cow dung, straw, and the leaves contain a certain amount of lignin, while chicken manure is mainly composed by carbonhydrate, protein, POC of C or D mainly comes from aliphatic higher plant source of stalks and leaves, POC of A comes from lignin of cow dung and microbial source aliphatic^[11], but the chicken manure has no source of lignin, because POC aromaticity of B is lower than other organic treatments. So, although the chicken manure resulted in POC aromaticity decline, it improves its hydrophobicity; leaves or cow dung greatly improves aromaticity, but it also improved the hydrophilic POC; there are both higher aromaticity and certain hydrophobic in straw fertilizer soil’ s POC, that is all the organic material who improved the aromaticity of POC, the stalk’ s hydrophilic is the lowest (the content of oxygen containing functional groups was 54.36%). It illustrated that in a short term, cow dung, straw or leaves can improve the stability of the POC, but for this short term conclusion needs to be further studied to confirm. From a long-term perspective, only straw fertilizer can guarantee the stability of POC, and a large number of studies have confirmed the stalk’ s function of carbon sequestration.

Fig.1

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	Fig.1 Cross polarization magic angle spinning 13C-NMR spectra of particulate organic carbon (POC) [A, B, C, D and CK] isolated from the soil

Table 1

Table 1

Table 1 Functional groups from the 13C NMR spectra samples Aliphatic carbon Methoxyl group carbohydrates Aromatic carbon Oxygen substituted aromatic carbon carboxyl carbonyl Aromaticity aliphaticity Oxygen- containing functional groups 0~45 ppm 45~63 ppm 63~93 ppm 93~148 ppm 148~165ppm 165~187 ppm 187~220 ppm % % % CK 24.08 16.72 10.03 13.71 6.69 7.69 21.07 20.40 79.60 62.21 A 24.57 19.16 12.53 15.48 5.16 7.62 15.48 20.64 79.36 59.95 B 31.36 14.41 11.02 14.83 5.51 6.36 16.53 20.34 79.66 53.81 C 30.71 12.03 10.37 14.94 5.81 8.30 17.84 20.75 79.25 54.36 D 18.64 18.64 12.07 18.37 6.04 7.87 18.37 24.41 75.59 62.99

Table 1 Functional groups from the 13C NMR spectra

As shown in Fig.2, the main absorption peak of sample’ s IR is caused by methyl C— H (2 920 cm^-1), methylene C— H (2 860 cm ^-1), aromatic groups C=C (1 620 cm^-1) and C— O (1 030 cm^-1) stretching vibration. The aromatic carbon’ s intensity of absorption bands at 1 620 cm^-1 is lower, significantly less than 1 030 cm^-1, that is POC has lower aromaticity and higher aliphaticity. The analysis results are consistent with the Nuclear Magnetic (Fig.1). The absorption band of 1 030 cm^-1 is caused by primary alcohol, ether, ester and carboxyl of C— O stretching vibration. The analysis results are consistent with the ¹³CNMR(Fig.1). Aromatic group absorption band of 1 620 cm^-1’ s intensity is A, C and CK obviously stronger than B, close to the Nuclear Magnetic results, while aliphatic carbon absosption band of 2 920 cm^-1 shows that B and C is stronger than other treatments, and it illustrated that B and C has higher content of aliphatic carbon, Same as the result of the ¹³C NMR (Table 1).

Fig.2

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	Fig.2 Infrared spectra (IR) of POC isolated from the soil