Effects Of Carbon Nitrogen Ratio And Microbial Inoculants On Corn Straw Fermentation

As a kind of agricultural waste, corn straw was lost seriously because of high annualproduction but low utilization in our country. Corn straw, a kind of materials contains avariety of nutrition elements, was changed into a cultivation matrix by fermentation. Withhigh carbon nitrogen ratio, corn straw would take a long time to be matured. Therefore, it’smeaningful to investigate the way to shorten the fermentation time.Selected corn straw as main material and urea as nitrogen source in this study, theeffects of carbon nitrogen ratio and microbial inoculants on corn straw fermemtation werestudied. Muturity index and its range of values have been picked up on the basis of relativedetermination indicators. The main experimental results are as follows:1. According to the detection of temperature, physical and chemical property andgermination index, the results showed that the C/N with25:1and35:1were in favor of cornstraw fermentation while the C/N with15:1was not. Among of them, the fermentation underthe treatment with C/N at15:1level was the worst, the temperature of corn straw changedquietly and had no high temperature phase during the whole fermentation period. Thedegradation rate of total organic carbon was slowest but the lost of nitrogen was serious.After50days of fermentation, the germination index was still lower than80%, whichproved the phytotoxicity has not been eliminated. Under the treatment with C/N at25:1level,the heating period was shortest but the high temperature duration was the longest （10days）,after29days of fermentation, the temperature dropped to below20℃. The degradation rateof total organic carbon was fastest while the loss of nitrogen was least. The germinationindex was reached up to80%in21days and85%in30days, higher than the othertreatments.2. The effects of microbial inoculants on corn straw fermentation at0.1%,0.3%and0.5%levels were investigated, taken the treatment without agent as comparison. The resultsshowed that, the heating durations were shortened by adding microbial inoculants, and thehigh temperature durations were extended in1-7days. Compared with non-agent treatment,microbial inoculants increased the average temperature as well as the top temperature.Microbial improved the degree of condensation of humus and the degradation rate of totalorganic carbon during the fermentation while the nitrogen lost was reduced. Microbialinoculants were in favor of the accumulation of nutrients and removed the phytotoxicity ahead of time. Compared among the treatments with different amount of microbialinoculants added, the results showed that the effects of microbial on corn straw fermentationwere promoted with the increased amount within a certain range, beyond the range, theamount was increased but the effects were reduced. The amount of microbial inoculantsadded at0.3%level was the best in this study.3. Selected the indicators have correlated to the change of germination index and C/Nas basic maturity indices. The degradation rates of ammonium nitrogen, ammonium andnitrate ratios, the degradation rates of total organic carbon and T-values, and the bulk densityof materials were determined to be the maturity index of corn straw fermentation finally.The results of the whole experiment showed that, at the time of corn straw matured or thegermination index reached up to85%, the range of the bulk density of materials were from0.11g·cm^-3to0.16g·cm^-3，the degradation rates of ammonium nitrogen were from24%to30%, NH₄⁺-N/NO₃^--N achieved2.3-3.0, the degradation rates of total organic carbon werefrom37%to44%, and the ratios of final C/N and initial C/N （T-Values） were at the range of0.65to0.85.