Effect of crop rotation on the diversity of the bacterial community colonizing rice straw residues in paddy rice cultured soil in the Mekong Delta of Vietnam

Abstract

In this study, the influence of crop rotation on the microbial diversity was investigated over a three crops. The studied crop rotation systems were rice-rice-rice (CRS1), rice-rice-baby corn (CRS2), rice-rice-mungbean (CRS3) and baby corn-rice-mungbean (CRS4).Litter bags containing rice stems were inserted into the soil and recollected at different time points for analysis and they were used to compare with the diversity of the bacterial community colonizing the rice straw by means of 16S rRNA gene based Denaturing Gradient Gel Electrophoresis (DGGE), UPGMA analysis and Shannon index (H) comparision. The results showed that the bacterial diversity colonizing rice straw residues were significantly different in composition in the (CRS4) rotation systemcompared to those in the 3 other systems.There were not significant differences in bacterial Shannon index during cultivation of crop I . In crop II and crop III, the CRS4 rotation system showed a H index higher than this of recorded in the CRS1, CRS2 and CRS3 treatments. The average H over the whole experiment was highest for the CRS4 system( H=1.13) and significantly different compared to the overall average H calculated for the other 2 systems CRS2(H=1.03) and CRS3( H=1.05) ,indicating that crop rotation with two upland crops was a vital key to the improvement of the Shannon index