Effects Of BADH Transgenic Maize Straw Decomposition On Soil Chemical Properties And Microbes

The BADH transgenic maize has the function of resisting abiotic stress such as drought,high salt and high osmotic pressure.It can effectively deal with the problems of crop quality decline and yield reduction caused by soil salinization.With the large-scale planting of BADH transgenic maize,the decomposition process of maize straw residues in soil,its impact on soil ecosystem and potential ecological risks have not been studied.In this study,four kinds of straws were selected,namely,straws of BADH transgenic maize BZ-136?NB?and non-transgenic maize Zheng58?NZ?planted in neutral soil,and straws of BADH transgenic maize BZ-136?AB?and non-transgenic maize Zheng58?AZ?planted in saline alkali soil.Soil samples SNB and SNZ were obtained after NB and NZ were buried in neutral soil for decomposition test,and soil samples SAB and SAZ were obtained after AB and AZ were buried in saline alkali soil.The basic properties and decomposition rate of straw,soil chemical properties,soil enzymes activity,microbial activity and bacterial and fungal community composition were analyzed.Prediction of bacterial and fungal genome function by PICRUSt and FUNGuild.The main results are as follows:?1?Comparison of basic properties between BADH transgenic and non-transgenic maize strawThe decomposition rate of AB was significantly higher than that of AZ?p<0.05?,but there was no significant difference in the cellulose decomposed amount compared with the latter.In early stage,the C decomposition rate of transgenic maize straw was higher than that of non-transgenic in different soil?p<0.05?,and the N decomposition rate of AB was significantly higher than that of AZ?p<0.05?.There was no difference in P and K decomposition rate.The glycine betaine?GB?in transgenic maize straw harvested from neutral or saline alkali soil was higher than that of non-transgenic?p<0.05?,and decreased with time,finally the difference disappeared.?2?Effect of decomposition of BADH transgenic maize straw on soil chemical propertiesThe decomposition of BADH transgenic maize straw slightly reduced soil p H and conductivity,but these effects were not significant.Transgenic maize straw could not cause significant changes in soil organic carbon,total nitrogen,available potassium and slowly available potassium,but increased the content of soil available N,total P and available P by 9.93 mg·kg^-1-14.68 mg·kg^-1,0.09 g·kg^-1-0.14 g·kg^-1 and 8.02 mg·kg^-1-11.58 mg·kg^-1?p<0.05?in early stage.?3?Effect of decomposition of BADH transgenic maize straw on soil enzymes activityThe urease activity increased significantly at 90 d,120 d and 150 d in the soil containing transgenic maize straw?p<0.05?,while the sucrase and alkaline phosphatase activity increased only in early stage?p<0.05?,the cellulase activity increased but not significantly?p>0.05?.The activity of protease,catalase,acid phosphatase and neutral phosphatase did not change significantly.?4?Effect of decomposition of BADH transgenic maize straw on soil microbial activityThe decomposition of BADH transgenic maize straw increased soil microbial biomass carbon?p<0.05?,and AB also increased microbial biomass nitrogen?p<0.05?.The bacterial number of SNB or SAB peaked at 30 d,which was 5.06×10⁷ CFU·g^-1and 4.47×10⁷ CFU·g^-1 respectively,and then decreased slowly,which was significantly higher than that of SNZ and SAZ at 30 d and 60 d?p<0.05?.The fungal number in the soil with transgenic maize straw increased first and then decreased slowly.The decomposition of transgenic maize straw increased the fungal number in early stage,but only at 90 d,there was a significant difference between SAB and SAZ?p<0.05?.The number of aerobic cellulose-decomposing microbes also increased but not significantly?p>0.05?.?5?Effect of decomposition of BADH transgenic maize straw on soil bacterial communityThe decomposition of BADH transgenic maize straw increased the OTUs number of soil bacterial community in some stages,but had no effect on Shannon and Chao1 index.At 60 d,the relative abundances of Proteobacteria in SNB and SAB increased by 4.29%and 2.96%?p<0.05?,the relative abundances of Limnobacter and Lysobacter in SAB were 0.011%and 3.61%higher than those in SAZ,respectively?p<0.05?,the relative abundance of Bacillus in the former was higher than that in the latter at 90 d?p<0.05?.The results of PCo A showed there was no significant difference in bacterial community composition of different soil.The results of PICRUSt analysis showed that there was no significant difference in bacterial metabolic function between SNB and SNZ,but there was significant difference between SAB and SAZ at 120 d?p<0.05?.?6?Effect of decomposition of BADH transgenic maize straw on soil fungal communityOTUs and Chao1 of soil fungal community increased by 127 and 145?p<0.05?at 60 d of AB decomposition,respectively,and Shannon index increased by 1.31?p<0.05?at 180 d.The fungal community composition in all soils was similar at phylum level,but at genus level,the relative abundances of Mortierella,Bullera and Cypellophora,Truncatella and Sebacina were changed at30 d,60 d and 90 d,respectively?p<0.05?.The relative abundance of Endophyte-Litter Saprotroph-Soil Saprotroph-Undefined Saprotroph guild increased by 0.63%at 30 d?p<0.05?,that of Plant Pathogen guild increased by 11.68%at 60 d?p<0.05?,and that of Ectomycorrhizal guild decreased by 0.13%at 120 d?p<0.05?,these changes were temporary.