Study On The Decomposition Of Crop Straw Under Anaerobic And Aerobic Condition

Straw residue incorporation,as an important biological resource for agricultural production system,is crucial for maintaining and improving soil fertility and crop yield.There are differences between anaerobic and aerobic condition during straw decomposition.FTIR?Fourier transform infrared spectroscopy?can indicate the dynamic changes of organic components during the decomposing process.Net bag method was applied to study the crop straw?wheat straw,rice straw,maize straw,rapeseed straw?decomposition?carbon,nitrogen mineralization,the residual quantity of cellulose,hemicellulose and lignin?and FTIR characteristic under anaerobic condition and aerobic condition during crop straw decomposition process.The decomposition regularity in field was analogous to that in laboratory.The main results are as follows:1?Residual mass of straw were significantly reduced?P<0.05?during the first 30 days,and then declined slowly during from 30 to 180 days.Residual mass of straw were remain stable between 180 and 360 days.Cumulative decay rate of straw mass were56.52%-75.23% and 75.61%-83.63% under anaerobic and aerobic condition,respectively.Residual quantity of straw-C and straw-N as well as cellulose,hemicellulose and lignin in straw were declined during the period of 360 days.As the decomposition rule of straw in the field was similar to that in the laboratory therefore,results obtained from indoor were emphasized in this paper.2?The residual mass,carbon and nitrogen of wheat straw sharply declined in the first3 months,and then slowly decreased from 3 to 12 months incubation period.The decomposition of wheat residues mineralization could be quantitatively described the by the first-order kinetics equation?the determination coefficient R2>0.957?.Half-lives?t 1/2?of wheat straw mass decomposition under aerobic and anaerobic conditions were 72.8 and122.0 days,and the decomposition rate constants?k?of wheat straw mass were 0.022 0 and0.014 0/d,under aerobic and anaerobic conditions,respectively.The decomposition rate constants?k?of straw-C and straw-N in wheat straw under aerobic conditions were 1.79 and 1.67 times higher than those under anaerobic conditions,and the biggest variations were found at the end of the first month.Cellulose,hemicellulose and lignin residues in wheat straw were gradually increased during the whole incubation period.These results indicated that the straw decomposition under aerobic condition were higher than that in theanaerobic condition.3?The rate of decomposition is faster in the initial stage and slower in the later during the rice straw incorporation.During the period of 360 days,the decomposition rate of rice straw was 66.44% and 71.41% under anaerobic and aerobic condition,respectively.Change of residual mass during the decomposition could be described by the first-order kinetics equation,the decomposing rate constant?K?were 0.019×d^-1 ? 0.020×d^-1 under aerobic and anaerobic conditions respectively.Half-lives?t1/2?of rice straw mass decomposition under anaerobic and aerobic conditions were 56.90 and 54.20 days,respectively.The rate of straw-N released was 66.37% and 72.16%.The residual nitrogen mass under anaerobic condition was 20.81% higher than that under aerobic condition.With the extension of incubation time,cellulose,hemicellulose and lignin residues in rice straw were decreased with the decomposing rate of 91.06%?90.00%?63.09% under anaerobic condition,which were lower than that under anaerobic condition.4?The residual quantity of chemical compositions in maize straw sharply declined in the first 90 days,and then slowly decreased from 90 to 360 days in incubation period.Change of residual rate during maize straw decomposition could be described by the first-order kinetics equation.Half-lives?t1/2?of maize straw mass decomposition under anaerobic and aerobic conditions were 79.87 and 52.89 days,respectively.And the decomposition rate constants?k0?of stalk-C in maize straw under anaerobic conditions?0.545/d?were lower than those under aerobic conditions?0.565/d?.The nitrogen cumulative released rate of maize straw under aerobic condition?74.20%?was higher than that under anaerobic condition?71.42%?.Cellulose,hemicellulose and lignin residues in maize straw were decreased during the whole incubation period.These results indicated that the straw decomposition under aerobic condition was higher than that under anaerobic condition,and the variations were gradually decreased during maize straw decomposition.5? The decomposition rate of rapeseed straw was higher at the beginning of the decomposing process,and then slowly decreased with time.During the decomposition process of 360 days,the decomposition rate of rapeseed straw under anaerobic and aerobic conditions were 60.50% and 68.20%,and the decomposition rate constants?k?were0.004×d^-1 and 0.010×d^-1,and half-lives?t 1/2?of rapeseed straw mass decomposition were229 and 117 days,respectively.The C releasing rates from rapeseed straw under anaerobicand aerobic condition were 70.33% and 77.43%,respectively.The C releasing rate constant?K?under anaerobic condition(0.025 × d?1?was lower than that under aerobic condition(0.026×d?1?.The nitrogen?N?releasing rates from rapeseed straw under anaerobic and aerobic conditions were 82.20% and 87.48%,respectively and the residues of nitrogen under anaerobic condition was 38.25% higher than that under aerobic condition?P<0.05?.The N residual rate from rapeseed straw under anaerobic condition was higher than that under aerobic condition,and the biggest variation was found during incubation period of60-90 days.6?The analytical results of the Fourier transform infrared spectroscopy showed that the absorption intensity at 3 430³ 430 cm^-1?the stretching of hydroxy?,2 925 cm^-1?the stretching of methylene?and 2 855 cm^-1?the stretching of methyl?band were significantly decreased,respectively,indicating that organic matter such as carbohydrate and aliphatic compounds decomposition declined during the decomposition process,while aromatic compounds were increased.The absorbance intensity at 1 419¹ 425 cm^-1 and 1 740 cm^-1,which were assigned to C=O stretching as well as C-O stretching and C-H deformation of the carboxylic acid functional group,respectively,were weakened,indicating that carboxylic acid lipid compounds and lignin content were decreased,and the absorption intensity under anaerobic condition was higher than that under aerobic condition.The silicon were released from crop straw and accumulated as oxides such as SiO2.Overall,during the process of straw decomposition,aliphatic compounds declined while aromatic compounds increased.The decomposition of cellulose,hemicellulose and lignin in aerobic condition was higher than that in the anaerobic conditions which resulted in the accumulation of aromatic property of residual straw.