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Abstract The oilseed cake, vetch, rapeseed straw, wheat straw and corn straw were buried in tobacco-planted soil. The decomposition rates, the variation of active organic C and N contents in the residues and the relationship between active organic C and N contents and decomposition rate were investigated. The results showed the decomposition rates of different organic materials were all high in the early period and then low in the late period. Among the organic materials, the decomposition rates ranked as oilseed cake > vetch > wheat straw and rapeseed straw > corn straw. The decomposition rate was positively related to total N content (P<0.01), but was negatively related to the active organic C/N ratio (P<0.01). However, there was no significant relationship between decomposition ratio and active organic C content. With the proceeding of decomposition, the active organic C content and the total N content in rapeseed straw, vetch, wheat straw and com straw all trended to increase, but the active organic C/N ratio trended to decrease. However, the variation of active organic C content, total N content and active organic C/N ratio in oilseed cake was on the contrary.
Key words Organic material; Decomposition rate; Active organic C; C/N ratio
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The organic materials contain rich mineral nutrients and organic carbon. When returned to soil, the organic materials will be decomposed by the soil microorganisms, thus the nutrients will be releases to soil and then absorbed and utilized by plants. The decomposition rate is an important indicator for evaluating the role of organic material in maintaining and improving soil organic matter distribution and soil fertility[1]. Currently, under field conditions, a lot of researches have been conducted on the decomposition rate of different organic materials and the effects of different utilization pattern on the decomposition rate. Among different organic materials, the decomposition rates ranked generally as leguminous crop straw > graminaceous crop straw0; graminaceous crop straw > rapeseed straw13'41; corn straw > wheat straw > rice straw15"*3; straw > stubble0; oilseed cake > straw181; crop straw > animal feces05'91. The effects of returning-to-soil pattern on the decomposition rate of organic materials are reflected as follows: burying > mulching0; 5 cm burying > 15 cm burying > open mulching >...