| The poor quality of soil seriously threatens food security and restricts the development of sustainable agriculture in saline-alkaline land.This study based on 3 years continuous field experiment and greenhouse experiment,respectively,to investigate the changes in morphophysiology,yields and qualities of oat,soil chemical-physical and biological properties,and system of the exduates-soil properties-microbial community(bacteria and fungi)between the rhizosphere and non rhizosphere,and between cultivars in four treatments:negative control(CK),bio-fertilizer(F),rotten straw(S)and the combination of the biofertilizer and rotten straw(FS)in this study.Aim to reveal the regulations and mechanisms of different amendments on the saline-alkaline ecological environments.It is expected to provide theoretical basis and technical supports for improving soil qualities and increasing crop yields and economical income in the saline-alkali land.The results show that:(1)For Baiyan2 and Caoyou1 two cultivars,F,S and FS treatments improved K+content of oat plants and grains,soluble sugar content(2016)of oat plants,and Na+ content of grains,but significantly reduced the Na+,soluble sugar,and organic acids(2017)content of oat plants which helps to improve the salt-tolerance of oats,so as to improve the root length,root volume,root surface area,root vigor of oats,yields of grain,fresh and hay forage yields.What is more,FS treatment was the optimal best one of methods,which could significantly improve the contents of crude protein,crude fat,neutral detergent fiber and acid detergent fiber of oats,compared with other treatments.F,S and FS treatments all could significantly increase the grain yield,fresh grass yield and hay grass yield of Baiyan 2 by19.49~146.05%,56.13~104.60% and 10.83~48.22% in 2017 that was second year of improving;F,S and FS treatments all could significantly increase the grain yield,fresh grass yield and hay grass yield of Caoyou1 of 56.98~140.69%,17.76~88.04%,28.99~120.42%.The 1000-grain weight and grain yield of Baiyan 2 under FS treatment were the highest,which were 21.6 g and 1709.9 kg hm-2,respectively.(2)F,S and FS treatments all could significantly reduce 0-40 cm soil p H and bulk density,and significantly increased the soil moisture,organic matter,available nitrogen,available phosphorus and available potassium,microbial biomass(carbon,nitrogen,phosphorus)and soil enzyme activities(catalase,sucrase,urease and alkaline phosphatase).FS treatment would be the best improved method while it led to higher soil EC.After 3 years of continuous improvement with planting oat,the total contents of cations(Ca2+,Mg2+ and Na+)decreased by 8.24%~82.78%,respectively,and SO42-decreased by 56.27%~80.88%,respectively,and soil K+ content increased by 49.65%~171.88%,respectively,in CK,F,S and FS treatments.According to the reduction range of soil cations Ca2+,Mg2+,Na+ and anion SO42-,FS treatment had better improvement advantage.The effect of soil watersoluble salt ions on oat quality was reduced in FS treatment,which effectively reduced salt damage in salt-alkali soil and improved the quality of grain and forage of oat.(3)Compared with the non-rhizosphere soils,rhizosphere soils bacterial phylum Actinobacteria,Gemmatimonadetes,Chloroflexi and fungal phyla Mucoromycota and genus Rhizopus were higher and bacterial phylum Proteobacteria,Bacteroidetes,and fungal phylum Ascomycota,Mortierellomycota and Aphelidiomycota were lower;The rhizosphere soils had lower soil p H,and higher soil microbial biomass carbon and nitrogen,NH4-N,NO3-N and total organic acids(mainly oxalic acid,formic acid,malic acid and acetic acid).Mucoromycota and Rhizopus were significantly increased in F treatment,especially in the rhizosphere soil,with higher organic acid.FS treatment significantly increased rhizosphere and non-rhizosphere soil harmful commnuties,including bacterial phylum Proteobacteria,Bacteroidetes,Firmicutes and fungal phyla Ascomycota,while significantly decreased benficial bacterial phylum Actinobacteria,Gemmatimonadetes and fungal phyla Mucoromycota and genus Rhizopus.Soil bacterial community richness and diversity were increased in S treatment,and soil fungal community richness and diversity were decreased in FS treatments.The results of this study showed that soil moisture,NH4-N,AK,carbohydrate,amino acid,soluble sugar and total organic acid contents,were the main driving factors of microbial community,and were all affected by the application of biofertilizer and rotten straw.(4)Higher bacterial richness,diversity,the bundance of phylum Acidobacteria and Proteobacteria(i.e.,Azotobacter and Pseudomonas)and fungal genus Gibberella,Talaromyces,Fusarium,Heydenia and Bipolaris,and lower exduates(soluble sugar,organic acids),abundance of bacterial Firmicutes(Bacillus)in rhizosphere soils for tolerant cultivar Baiyan2 than in rhizosphere soils for sensitive cultivar Caoyou1.F treatment signicantly increased beneficial bacteria such as Proteobacteria and fungal Rhizopus Arrhizus,and reduce pathogenic bacteria related to Firmicutes,Ascomycota(genus Alternaria,Cladosporium,Sarocladium and Heydeni),which might be related to the significant increased in organic acids content and the significant decreased in soil p H;S and FS treatments significantly reduced the rhizosphere soil bacterial community richness,diversity,the abundance of Proteobacteria,Acidobacteria,and fungal Mucoromycota and Zygomycetes(Rhizopus arrhizus)related beneficial micorbes,while increased the bacterial community richness,diversity and Ascomycetes related pathogenic microbes,which all affected by increased of the contents of soil salt and available nutrients(N,P,K),and decresed of the contents of soil exudates(soluble sugars and organic acids).However,FS treatment did not significantly change the rhizosphere soil fungal community of Baiyan 2.In conclusion,co-application of rotten straw and bio-fertilizer combined with planting of saline-alkaline tolerant oat varieties has more advantages for improvement,and can be used as one of the methods to improve soils and increase crop income in a saline-alkaline land. |
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