| Leymus chinensis is an ecologically important grass that is widely distributed in northern China and is a native rhizome grass with high nutritions and yields.Soil nutrients usually decline along with the harvest of grass and other agricultural production(livestock feeding,mowing,etc.).Fertilization is considered as an effective approach to replenish the soil nutrients in order to regenerate the grasslands.However,the application of chemical fertilizer is not an integrated approach for both improvement of grassland productivity and soil sustainable development.Bio-fertilizer can have beneficial effects on soil microflora,thus effectively improving soil microbial activities,increasing nutrient availability,and enhancing soil fertility,which has been widely applied in the agricultural field.To the best of our knowledge,studies on the practical effects and soil microbial ecological regulation mechanisms of bio-fertilizers in artificial grasslands have rarely been reported.We conducted in situ and pot experiments to investigate the practical effects of different fertilization regimes on Leymus chinensis growth,with a focus on the potential microbal ecological mechanisms underlying the responses of soil microbial composition.The results were obtained as follows:1)The strains of Trichoderma were isolated from the soil that collected from in suit field.A total of 119 Trichoderma strains were obtained,which mainly contained 5 genera:Trichoderma harzianum,Trichoderma pseudokoningii,Trichoderma citrinoviride,Trichoderma rossicumi and Trichoderma tomentosum.The growth speed of Trichoderma and its promotion effect on Leymus chinensis seedlings were considered as preliminary and secondary screening indicators,based on which NAU-18(Trichoderma rossicumi)was chose as the optimal strain.2)In the in situ fertilization experiment,OF1(3000 kg hm-2 organic fertilizer),BOF1(3000 kg hm-2 bio-organic fertilizer),OF2(6000 kg hm-2 organic fertilizer),BOF2(6000 kg hm'2 bio-organic fertilizer),OF3(9000 kg hm-2 organic fertilizer)and BOF3(9000 kg hm-2 bio-organic fertilizer)treatments increased L.c1inensis biomass by 7.0%,16.0%,42.1%,8.8%,71.8%,and 118.8%,respectively,compared to CK(non-amended fertilizer).Bio-organic fertilizer application significantly(P<0.05)increased L.chinensis biomass as compared with organic fertilizer application.The maximum L.chinensis biomass measured was from BOF3(236.02 g m-2),which higher than other treatments.Different fertilization regimes had different effects on soil physicochemical properties.The soil total P contents in fertilization treatments are significantly(P<0.05)higher than CK,while there is no significant difference among fertilization treatments.The soil available P contents in OF2 and BOF2 are significantly(P<0.05)higher than other treatments.BOF3 had the highest contents of soil total K and available K,which significantly(P<0.05)higher than other treatments.In the pot experiment,L.chinensis biomass and soil physicochemical properties showed the same tendency as those in the in situ fertilization experiment.3)The application of bio-organic fertilizer(BOF,6000 kg hm-2)significantly(P<0.05)increased the bacterial ?-diversity and decreased the fungal ?-diversity,as compared with CK.Different fertilization regimes had significant(P<0.05)influence on soil microbial community structure.For the common beneficial genera,BOF treatment significantly(P<0.05)resulted in the enrichment of the genera Trichoderma,Adhaeribacter,Flavobacterium and Bacillus.For the possible pathogenic genera,BOF significantly(P<0.05)reduced the abundance of the fungal genera Fusarium,Alternaria and Penicillium.The RDA showed that organic matter,total N and available K content play a greater role than others in relation to the relative abundance of these soil beneficial microbial genera:Trichoderma,Adhaeribacter,Flavobacterium and Pseudomonas.In conclusion,Trichoderma bio-fertilizer(BOF,6000 kg hm'2)effectively influenced soil microbial community,thus improving L.chinensis biomass.6000 kg hm-2 was recommended as the optimal fertilization level for L.chinensis growth,which is benefit for sustainable soil fertility and provides an important theoretical basis for constructing high-yield microflora of L.chinensis. |
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