Influence Of Seaweed On Different Plant-growth Promoting Microorganisms And Its Application

Seaweed is an inferior cryptogamous plant in the sea. The nutrients of seaweeds are greatly different from that of plants on land because of their particular environment. Seaweed contains rich minerals and vitamins that are much less in amount in ordinary plants on land. Seaweed and its products are now widely used in many fields. Seaweed has gained application in the field organic agriculture as biostimulants and fertilizer. In this article, the rich resources of Laminaria japonica and Entermorpha on the sealine of Tsingtao, Shandong Province are used as raw materials to study the effect of liquid seaweed extract on the growth of PGPR(plant growth-promoting rhizobacteria), the production process of seaweed organic fertilizer and the effect of the application of seaweed fertilizer on the chemical properties of orchard soil and the amount, activity and community structures of soil microorganisms.1/100, 1/200, 1/500, 1/1000 proportional seaweed liquid extract was added to LB liquid medium (v/v). Four species of PGPR (plant growth-promoting rhizobacteria), Azotobacteria, organic phosphobacteria, inorganic phosphobacteria, and silicate-dissolving bacteria were inoculated to the medium and OD values were measured at different time points. The result indicates that adding seaweed liquid extract has no significant influence on the growth of organic phosphobacteria while promoting the growth of azotobacteria, inorganic phosphobacteria, silicate-dissolving bacteria. The different quantities of seaweed liquid extract added have no significantly different growth-promoting effect on azotobacteria and inorganic phosphobacteria. Adding 1/1000 proportional seaweed liquid extract would have significant growth-promoting effect. In the case of silicate-dissolving bacteria, the growth-promoting effect becomes stronger as the quantity of seaweed extract becomes greater, being best when adding 1/100 proportional seaweed extract.Seaweed organic fertilizer was manufactured from Laminaria japonica and Entermorpha on the sealine of Tsingtao, Shandong Province, by high-temperature fertilization. An apple orchard planted with trees 10 years old in Yantai, Shandong Province was chosen for the experiment. The fertilizer was applied in the autumn of 2008. The two species of fertilizer were applied with the same amount, each applied with three different quantities, 7.5, 15, 22.5kg/plant to the orchard. The orchard was managed as usual. The control sites with no organic manure were established at the same time. To maintain the production of apple trees, chemical fertilizer were applied to all the experimental sites with the same amount. Soil samples were collected in May and October the next year. The effect of seaweed fertilizer on the amount, activity and community structure of soil microorganisms was studied using dilution plating, measuring soil enzyme activities and forming microbial community FAME (fatty acid methyl ester) profiles.The result indicates that Laminaria japonica organic fertilizer and Entermorpha organic fertilizer significantly increase the contents of organic matter, total nitrogen , available K and available P in orchard soil. Laminaria japonica organic fertilizer and Entermorpha organic fertilizer can increase the soil pH value and improve the quality of acidic soil. The Laminaria japonica organic fertilizer has better effect than Entermorpha organic fertilizer.The analysis of soil samples collected in May indicates that Laminaria japonica organic fertilizer and Entermorpha organic fertilizer significantly increase the amounts of culturable bacteria and actinomycetes in soil. The amount of bacteria is 2.81-9.30 times higher than that in control soil. The amount of actinomycetes is 1.95-18.62 times higher than that in control soil. The application of Laminaria japonica fertilizer and Entermorpha fertilizer has no significant influence on the amount of culturable fungi. Laminaria japonica organic fertilizer and Entermorpha organic fertilizer significantly increase FDA (Fluorescein diacetate) enzyme activity and urease activity in soil. FDA enzyme activity is 1.25-1.88 times higher than that in control soil. Urease activity is 1.71-2.79 times higher than that in control soil. The application of Laminaria japonica fertilizer and Entermorpha fertilizer has no significant influence on catalase activity. The analysis of FAME indicates that both Laminaria japonica organic fertilizer and Entermorpha organic fertilizer significantly increase microbial biomass. The total FAME amount is 1.60-2.64 times higher than that in control soil. The application of Laminaria japonica fertilizer and Entermorpha fertilizer increases the relative abundance of monounsaturated fatty acids in soil microorganisms, being 1.14-1.64 times higher than that in control soil. The principal components analysis on FAME data indicates that soil microbial community structures are much changed due to the application of Laminaria japonica organic fertilizer and 22.5kg/plant Entermorpha organic fertilizer. However, 7.5kg/plant and 22.5kg/plant Entermorpha organic fertilizer have little effect on microbial community structures. Both fertilizers have much less effect on soil microorganisms in the analysis of soil samples collected in October. These results indicate that the application of Laminaria japonica organic fertilizer and Entermorpha organic fertilizer has beneficial effect on orchard soil quality.