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Returning organic materials is recognized as an effective practice to alter soil organic carbon (SOC) content, in which microorganisms play a critical role. The objective of this study was to evaluate the effects of different kinds of animal manure combined with stover (AM-S treatments) on labile organic C fractions and soil microbial community. The two-year experiment involved four treatments: maize stover only (S), maize stover plus ox manure (SO), maize stover plus chicken manure (SC), and maize stover plus pig manure (SP). In 2018 and 2019, AM-S treatments increased the levels of SOC, dissolved organic carbon (DOC), easily oxidized carbon (EOC), microbial biomass carbon (MBC), and maize yields. Maize stover plus ox manure treatment could provide better accumulation of MBC, and enhance bacterial and fungal richness and diversity. Maize stover plus pig manure treatment enhanced the contents of DOC and maize yield and also recorded the highest percentage of Proteobacteria (57.6%). Also, the EOC contents were 13.0% and 21.5% higher than SO and SC respectively. In all, our findings suggested that the application of maize stover plus pig manure was the most effective treatment for enhancing labile SOC fractions and improving the microbial community. [ABSTRACT FROM AUTHOR]

The structures of soil humus (HS) amended with organic wastes (OWs) were closely related to properties of OWs-derived humus-like substances (HSL). This work evaluated the properties of HSL isolated from mushroom residue (MR), chicken manure (CM), sheep manure (SM), tree leaves (TL), maize straw (MS) and fodder grass (FG) and studied the structures of soil humic acid (HA) and fulvic acid (FA) amended with these OW. FTIR results showed that the relative intensities at 1,640 cm−1 peaks of TL-, FG- and SM-derived HAL were higher than other CM-, MS- and MR-derived HAL (p < 0.05), while the 2,930/1,640 ratios were lower (p < 0.05). Relatively lower E4/E6 ratios and ΔlogK values of TL-, FG- and SM-derived HAL were recorded (p < 0.05). Relative intensities at 1,620 cm−1 peaks of soil HA and soil FA amended with TL, FG and SM were higher than other OWs, while the 2,930/1,620 ratios were significantly lower (p < 0.05). The 2,930/1,620 ratio of soil HA and soil FA amended with MS and CM was the highest, respectively. In conclusion, the properties of OWs-derived HSL play important roles in functional groups of soil HS amended with these OWs. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the variation in labile organic carbon fractions after the application of organic wastes (OWs) in semiarid soil under plastic mulched drip irrigation. The two-year experiment involved six treatments: chicken manure (CM), sheep manure (SM), mushroom residue (MR), maize straw (MS), fodder grass (FG), and tree leaves (TL), with an unamended soil (no OWs) as control. In 2015 and 2016, treatment with OWs led to increased levels of soil organic carbon (SOC), dissolved organic carbon, microbial biomass carbon, easily oxidized organic carbon, as well as higher carbon management indexes and yields and lower oxidation stability coefficients. Higher SOC contents (p <0.01) were achieved in both years for TL and MS compared to the other OWs. In particular, the SOC content in 2016 was higher (p <0.05) for TL than MS. Compared to the other OWs, the easily oxidized organic carbon levels and carbon management indexes in both years were higher (p <0.01) for CM, SM, and MS, whereas the oxidation stability coefficients were lower (p <0.01). In conclusion, among the studied treatments, the application of MS was the most effective for improving soil fertility and enhancing soil carbon sequestration. [ABSTRACT FROM AUTHOR]