Effects Of Noval Strain Of The Lysobacter Enzymogenes (LE16) On Degradation Of Soil Organic Nitrogen And Phosphorus And Crop Growth

In agricultural production,in order to ensure the yeild of agricultural products,people apply a large amount of chemical fertilizers,especially nitrogen and phosphorus fertilizers,which had caused a series of soil,production and environment problems,such as soil compaction,waste of fertilizer resources,low fertilizer nutrient utilization,poor crop quality and environmental pollution,etc.Activate of soil unavailable nutrients is beneficial to soil nutrient recycle and utilization,reduce the amount of fertilizer use and increase efficiency,and sustainability of high crop yeiled and quality.Plant growth-promoting rhizobactera(PGPR)have a variety of functions,such as the synthesis of many plant phytohormones(IAA,GA,etc.),secretion of antibacterial substances,mobilization of soil insoluble nutrients,increase of crop seed germination rate,promotion plant growth and development,and improvement of plant disease resistance.Therefore,it is important to select and apply effective plant growth-promoting rhizobactera(PGPR)for the application of PGPR.The present experiment was carried out to investigate the effects of a self-isolated noval biocontrol Lysobacter enzymogenes(strain LE16)bacteria suspension on organic nitrogen(N)and organic phosphorus(P)activation in the soil,crop seed germination and plant growth via soil pure incubation,seed germination,and greenhouse pot experiments.The objective of this study is to provide the scientific bases for Lysobacter enzymogenes LE16 application.At the same time,it also provides scientific theoretical basis for the fertilizer-loss and efficiency-improving cultivation of Brassica campestris L.spp.and Avena nuda L..The application of L.enzymogenes LE16 also contributes to resource conservation and environmental protection.Following are the main research results obtained:1.In the laboratory pure soil incubation experiment,the sloping soil and vegetable soils were inoculated L.enzymogenes LE16.The results showed that the numbers of this bacterium(L.enzymogenes LE16)increased to the maximum 8.2 Lg CFU g^-1 soil and8.3 Lg CFU g^-1 soil,respectively.And then the number of this bacterium(L.enzymogenes LE16)dropped to maintain at a stable state in the soils during the incubation period.At the same time,the content of alkaline N,ammonium nitrogen(NH₄⁺-N),and protease activity increased with the increasing L.enzymogenes LE16inoculation time in the sloping soil and vegetable soils.In addition,inoculated L.enzymogenes LE16,resulting in positive correlations among alkaline N,ammonium nitrogen(NH₄⁺-N)and protease activity in sloping soil and vegetable soils.During the whole soil culture period,there was a significant positive correlation between protease activity and alkaline N(r=0.885^**,n=30,P<0.01)and ammonium nitrogen(NH₄⁺-N)(r=0.963^**,n=30,P<0.01)in sloping soil.And there was a significant positive correlation between protease activity and alkaline N(r=0.964^**,n=30,P<0.01)and ammonium nitrogen(NH₄⁺-N)(r=0.960^**,n=30,P<0.01)in vegetable soil.In the vegetable soil,acid phosphatase activity was also positively correlated with Olsen P and water-soluble P(r _{Olsen P}=0.929^**,r _{water-soluble P}=0.861^**,n=30,P<0.01).2.The seed germination test of Brassica campestris L.spp.and Avena nuda L.suggested that noval biocontrol Lysobacter enzymogenes LE16 signifciantly promoted seed germination and seedling growth of Brassica campestris L..Among them,compared with blank contral treatment(CK),inoculated concentration of 1×10⁷ CFU m L^-1(BI7)Lysobacter enzymogenes LE16 bacterial suspension,Brassica campestris L.spp.seed germination index,vigor index,leaf chlorophyll content,root vigor,leaf nitrate reductase activity,plant height,biomass increased by 20.32%,67.54%,20.39%,86.05%,29.86%,39.48%and 20.41%,respectively.Inoculated concentration of 1×10⁸CFU m L^-1(BI8)Lysobacter enzymogenes LE16 bacterial suspension,Brassica campestris L.spp seed vigor index,leaf chlorophyll content,root vigor,leaf nitrate reductase activity,plant height,biomass increased by 42.80%,27.16%,74.08%,46.49%,53.22%and 36.73%,respectively.However,comprehensively,the promotion effect of BI8 treatment is better.At the same time,inoculation with strain L.enzymogenes LE16 also increased the number of main roots and root vigor of Avena nuda L..Among them,compared with blank contral treatment(CK),inoculated concentration of 1×10⁷(BI7)CFU m L^-1 Lysobacter enzymogenes LE16 bacterial suspension,the number of roots and root vigor of seedlings increased by 51.76%and36.00%,respectively.Inoculated concentration of 1×10⁸(BI8)CFU m L^-1 Lysobacter enzymogenes LE16 bacterial suspension,the number of roots and root vigor of seedlings increased by 20.08%and 20.00%,respectively.Howere,there were no significant differences between BI7 and BI8 treatments.3.The greenhouse pot experiment of Brassica campestris L.spp.and Avena nuda L.indicated that the strain L.enzymogenes LE16 inoculant increased the NPK nutrient absorption of Brassica campestris L.spp.and Avena nuda L..This bacterial suspension(concentration of 1×10⁸ CFU m L^-1 Lysobacter enzymogenes LE16)also increased protease and phosphatase activities,availiable N and P,and microbial biomass C and microbial biomass N in Brassica campestris L.spp.and Avena nuda L.rhizosphere soil.Compared with the only chemical fertilizers CF treatment,application of chemical fertilizers in combination with bacterial inoculant and 85%chemical fertilizers in combination with bacterial inoculant significantly increased economic yield of Brassica campestris L.spp.by 24.74%(CF+BI)and 8.38%(0.85 CF+BI).After use L.enzymogenes LE16 inoculant,the grain yield of Avena nuda L.followed a similar trend to Brassica campestris L.spp..Among them,compared with the only chemical fertilizers CF treatment,application of chemical fertilizers in combination with bacterial inoculant significantly increased economic yield of Avena nuda by 31.17%(CF+BI)and 31.69%(0.85 CF+BI).In addition to the increased yields,L.enzymogenes LE16also improved the quality of the both..Compared with the only chemical fertilizers CF treatment,Degradation;Brassica campestris L.spp.;Avena nuda L.;growth promotionthe maximum increased in soluble sugar and vitamin C content of Brassica campestris L.spp.with chemical fertilizers and bacterium(CF+BI and 0.85 CF+BI)were 51.45%and 19.79%,and the maximum nitrate content was reduced by 51.78%.The crude fat of Avena nuda L.increased by 36.44%,and the maximum increase of crude protein in plant and grain were 11.16%and 8.99%,respectively.