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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]

Poor soil fertility conditions limit agricultural production and development in saline-alkali areas. At the same time, in order to solve the problem of environmental pollution caused by agricultural wastes, agricultural wastes are used for organic fertilization of saline-alkali soils. In this study, the amount and structure of soil dissolved organic carbon after the application of different organic wastes was assessed. The results showed that the content of dissolved organic carbon in each component increased significantly (p <.05), while treatment GS recorded the highest content of dissolved organic carbon in each organic carbon component. The UV-visible spectrum of soil dissolved organic carbon recorded different results after the application of organic materials. For water-soluble organic carbon (WSOC), treatment CS was most effective in increasing the molecular weight of soil WSOC while treatment GS was most beneficial in improving the hydrophobicity and aromaticity of soil WSOC. For thermal hydrolyzed organic carbon (THOC), treatment GS was most effective for increasing the molecular weight and hydrophobicity, while treatment SM was most beneficial for increasing aromaticity. For hydrochloric acid and hydrolyzed organic carbon (HHOC), treatment SM was most effective in increasing molecular weight, while treatment FG and GS were most beneficial in improving the hydrophobicity and aromaticity of HHOC. For Alkali hydrolysis of organic carbon (AHOC), treatment GS was most beneficial for increasing the molecular weight, aromaticity, and hydrophobicity of AHOC. Amongst all the treatments the organic material treatments increased the aromaticity, hydrophobicity, molecular weight, and humification degree of soil soluble organic carbon compared with CK. [ABSTRACT FROM AUTHOR]

Soil available nutrients and soil salt ions are considered to play a significant role in soil fertility. A two-year field experiment was conducted to investigate the effects of different agricultural organic wastes on soil available nutrients and soil ions in a primary saline soil, located in the west of Jilin Province, China. The treatments were granular corn straw (GS), coarse corn straw (CS), sheep manure (SM), fodder grass (FG), and control (CK). The results showed that agricultural organic wastes effectively decreased soil pH by 1.28%-3.83%. The application of agricultural organic wastes also improved soil available nutrients, of which the available nitrogen (AN) increased by 23.64%-32.54%, the available phosphorus (AP) increased by 16% −19.93%, and the available potassium (AK) increased by 2.78% – 8.42%. In contrast, the content of soil salt ions decreased significantly with the exception of potassium ions. Linear dependence suggests that, with the decrease of soil pH, the soil available nutrient content was higher. From the correlation analysis, the relationship between other salt ions and soil available nutrients showed an extremely significant negative correlation with the exception of potassium (K+). The redundancy analysis (RDA) showed that calcium (Ca2+) and potassium (K+) are the main factor affecting soil available nutrient content in 2a (about 12 months after organic wastes were applied) and 3a (about 24 months after organic wastes were applied), respectively. In conclusion, treatment GS is recommended for improving soil available nutrients and decreasing the pH and content of soil salt ions in primary saline-alkali soils. CK: control without orgaanic material; GS: granular corn straw; CS: coarse corn straw; SM: sheep manure; FG: fodder grass; AN: available nitrogen; AP: available phosphorus; AK: available potassium; RDA: redundancy analysis; 1a: before the application of organic wastes; 2a: about 12 months after organic wastes were applied (first year); 3a: about 24 months after organic wastes were applied (second year). [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]

In order to evaluate the effects of different maize straw returning modes on humus composition and humic acid (HA) structural, a field experiment was designed to have five treatments, i.e. Treatment CK (no straw returned), Treatment EIS (straw incorporated evenly into the soil using the crashing-ridging technique), Treatment SP (straw plowed into the soil), Treatment SM (straw returned as mulch) and Treatment SG (straw returned as pellets). Our results showed that Treatment EIS significantly increased the content of soil organic carbon (SOC), soil humus substances (HEC), soil humic acid carbon (HAC) and fulvic acid carbon (FAC) by 27.8%, 47.6%, 63.3% and 33.8%, respectively, as compared with CK. Among all the straw returning treatments, Treatment EIS was the most significant in effect of increasing the content of HEC, HAC and FAC. Moreover, Treatment EIS altered the composition of humus more significantly than all the other treatments, by increasing the proportion of alkyl C and the ratio of aliphatic C/aromatic C. These results suggest that straw returning accelerated the accumulation of soil organic C and various components of humus, significantly improved the structure of soil HA, with the practice of EIS in particular. [ABSTRACT FROM AUTHOR]