Effects Of Straw Returning Methods On Arbuscular Mycorrhizal Fungal Community And Phosphorus Utilization In Maize

As a typical soil in southern China,red soil had serious problems including acidification,poor nutrients,and degradation of soil biological functioning.Straw returning has been proposed as an effective method to improve the fertility of red soils.In this study,we performed a long-term field experiment of straw returning with equal carbon content in the Red Soil Agroecosystem Experiment Station of the Chinese Academy of Sciences in Yingtan Jiangxi Province.Five fertilization treatments were set up: no fertilization(CK);conventional NPK(N);NPK + straw returning(NS);NPK +straw returning combined with pig manure application(NSM)and NPK + straw biochar(NB).High-throughput sequencing was used to estimate effects of straw returning treatments on the diversity and structure of rhizosphere arbuscular mycorrhizal fungal community and corn phosphorus utilization efficiency.The main results were shown as follows:1.It was found that soil features were affected significantly by different treatments of straw returning.Soil organic carbon(SOC)content under the NB treatment was significantly higher than those under the NSM and NS treatments.Total phosphorus(TP),available phosphorus(AP)and phosphorus activation coefficient(PAC)under the NSM treatment were significantly higher than those under the NS and NB treatments.Total nitrogen(TN)and total potassium(TK)under the NSM and NB treatments increased more significantly than that under the NS treatment.2.The diversity and structure of rhizosphere AMF community under different straw returning treatments: Straw returning significantly increased the AMF diversity.The Chao1 and richness indexes were the highest under NSM treatment,following the trend of NSM>NS?NB>N>CK.There was no obvious difference in the richness index among three treatments of straw returning.Principal coordinate analysis(PCo A)analysis showed that AMF community structure were significantly affected by different treatments of straw returning,which TP,TK,TN,and AP were the mainly influencing factors.The analysis of the phylogenetic tree revealed that the dominant genera in the rhizosphere AMF community were Paraglomus(48.51%),Glomus(26.73%),Ambispora(7.92%),Acaulospora(6.93%),Scutellospora(4.95%),Diversispora(3.96%),and Archaeospora(0.99%).The abundance of Glomus under the NS and NB treatments was significantly higher than that under NSM treatment,while Paraglomus followed the opposite trend.Pearson correlation showed that Chao1 and richness were positively affected by SOC,TN,TP,AP,CEC,and PAC.Random forest model indicated that AP,TN,PAC,TP,and p H were the primary factors shaping the AMF community diversity.3.The co-occurrence network analysis showed that the interaction networks of AMF community were obviously different under different treatments of straw returning.The AMF network under the NSM treatment was the most complicated,dominantly by negative correlations.Under the CK and NSM treatments,the proportion of nodes belonging to Paraglomus in AMF networks was higher than that of Glomus,whereas the N,NS and NB treatments showed the opposite trends.Compared with the CK treatment,the N,NS,NSM,and NB treatments significantly improved network stability(natural connectivity),with the increase under the NSM treatment was the highest.Keystone taxa of the AMF network under the NB treatment belonged to Glomus,while those under the CK,N,NS,and NSM treatments belonged to Paraglomus.Pearson correlation analysis between the modules of AMF networks and soil features indicated that the module I of AMF network was positively correlated with soil phosphorus under the CK treatment.Three modules of AMF network under the N and NB treatment was associated with soil phosphorus.Four modules AMF network under the NS network exhibited the significantly associations with TN and AP.The NSM network has the most modules which closely correlated to soil features.4.The ?-null deviation(NDV)analysis revealed that straw returning caused an gradual increase in the stochastic process of AMF community assembly,although the deterministic process was dominant.The niche width of the dominant genera Glomus and Paraglomus exhibited the similar trends with that of the entire AMF community(NSM>NB>NS>N>CK).The NDV value of AMF community showed a trend of NSM>NS>NB,as well as that of the dominant Glomus.The soil variables(TP,p H,AP,and PAC)and biological factors(AMF diversity and community composition)were significant determinants in driving the assembly processes of the AMF community.5.Acid phosphatase(ACP)activity(NSM>NB ? NS>N ? CK)and alkaline phosphatase(ALP)activity(NSM?NB>NS?N?CK)under different treatments of straw returning followed the different trends and ACP activity was higher than ALP activity.The ACP and ALP activities were significantly affected by soil features(SOC,TN,AP,and PAC)and biological factors(diversity,percentage of negative correlation).The dry weight of grain,dry weight of straw and aboveground biomass under different treatments of straw returning had similar trends of NSM>NS?NB>N>CK.Correlation analysis found that corn yield was obviously affected by soil features(AP,PAC,p H,TP,CEC,SOC,TN)and biological factors(diversity,percentage of negative correlation).The apparent and economic utilization rate on phosphate fertilizer followed the trend of NSM>NS>NB>N.The apparent and economic utilization rate of phosphate fertilizer under the NSM treatment were significantly higher than those under N,NS and NB treatments.The apparent and economic utilization rate were mainly affected by soil features(AP,PAC,TP),PNC,ACP,ALP activity,grain dry weight and aboveground biomass.SEM revealed that soil features(AP and TP)could indirectly affect phosphorus utilization by affecting AMF community composition and network,phosphatase activity,and plant productivity.Our results highlights the importance of rhizosphere AMF community for strengthening soil health and crop production capacity.