The Humuns Transformation Mechanism Research During Composting Under Different Controlled Conditions

In order to systematically explore humus transformation mechanisms during composting under different controlled conditions. Lots of composting experiments were arranged. The impact of turning frequency and coverage conditions under different seasons, different ventilation rate and way, and different chemical additives on transformation of humus during the composting process has been systematically studied, and also the impact on crop and soil humus after compost applied to the soil was studied. Structural characteristics of humus in the composting had been studied by elemental analysis, FT-IR and GC-MS analysis technology. The main research conclusions are as follows:(1) The composting significantly improved the humic acid carbon, nitrogen accounted for the proportion of the humus carbon, nitrogen. Volatile substances degradation rate in warm season was higher than in the cold season. After70days composting, humus carbon (HS-C) accounted for the proportion of TOC and the rate of increase in cold season were both higher than in the warm season. Turning could significantly reduce the E4/E6valueof humic acid.(2) Excessive ventilation rate resulted in a large number of heat and moisture loss during composting. Volatile substances degradation occurred mainly in the heating and thermophilic phase. Intermittent ventilation compared to continuous ventilation, the variation of HS-C accounted for the proportion of TOC was much larger, but the ratio of humic acid nitrogen (HA-N) and fulvic acid nitrogen (FA-N) under continuous ventilationand was higher than the intermittent ventilation. After composting, the C/N of fulvic acid under forced ventilation treatments was higher than non-ventilation treatment, and ventilation significantly reduced the humic acid E4/E6value.(3) Chemical additives could reduce the degradation rate of the volatile substances during the composting, and superphosphate+magnesium chloride treatment not only reduced the loss of volatile substances, but also reduced the content of humic acid in the humus, however, it can significantly improved the porportion of humus nitrogen (HS-N) in the total nitrogen. The humus nitrogen accounted for the proportion of the total nitrogen in the compost was positively correlated with the content of ammonium nitrogen. The ratio of humic acid carbon and fulvic acid carbon (HR=HA-C/FA-C) and the ratio of humic acid carbon and humus carbon (HP=HA-C/HS-C) changed intensely in the heating and thermophilic phase. Compared to mushroom compost and sawdust compost, corn straw compost was more favorable to humification of organic carbon.(4) When compost applied to the soil, it affected the corn yield by corn rows per ear and kernels per row, and it was more conducive to the accumulation of soil organic matter compared with fertilizer treatment. Compost treatments significantly increased the content of soil total nitrogen, the greatest increase happened in the adding superphosphate15%treatment. Content of soil fulvic acid carbon (FA-C) after two-years rotation were different degrees of decline, but a significant increase in the content of soil humic acid.(5) The changes in the structure of humic acid and fulvic acid mainly happened in maturity stage. The aromatization extent of humic acid was higher than fulvic acid, the type of humic acid was Rp in the composting process, and still was relatively immature compared to soil humic acid After70days windrow composting, the structure of fulvic acid included phenol, alkanes, methyl ester, amide. Structure of humic acid contained alkanes, benzene, phenol, lipids, amides, and mainly was lipids and amides.