Study On The Recycling Potential Of Falling Flowers Of Common Green Trees In Northern Cities

In order to explore the recycling potential of falling flowers of common greening trees in northern cities,in this study,14 kinds of falling flowers,such as Cerasus sp.,Malus spectabilis,Magnolia denudata,Magnolia liliflora,Amygdalus persica,Prunus cerasifera Ⅰ,Prunus cerasifera Ⅱ,Michelia figo,Cercis chinensis,Prunus mume,Ginkgo biloba,Koelreuteria paniculate,Armeniaca vulgaris and Forsythia suspense,were selected as objects,two experimental studies were carried out: 1)To study the decomposition and nutrient release characteristics of the falling flowers of greening trees by using nylon mesh bag burial decomposition method,with the aim of providing a scientific basis for using the falling flowers of greening trees as fertilizer material for agricultural fields(crushed and applied directly or as an additional material for biomass organic fertilizer).2)Using the Petri dish filter paper method to study the allelopathic effects of the water extract of the falling flowers of the greening trees on the seed germination and seedling growth of Cucumis sativus,Sorghum vulgare,Triticum aestivum and Brassica campestris,with the aim of providing a scientific basis for effectively avoiding the allelopathic inhibitory effect on crops when using falling flowers as fertilizer.The main results are as follows:(1)Among the falling flowers of all green tree species,the crude protein content was higher in Magnolia denudata and Amygdalus persica(251.44-274.94 mg/g),lignin content was higher in Cercis chinensis and Ginkgo biloba(47.35-49.95 μg/g),N content was higher in Magnolia denudata and Amygdalus persica(40.23 43.99 mg/g),P content was higher in Magnolia denudata and Amygdalus persica(1.37-1.58 mg/g),K content was higher in Magnolia denudate,Prunus cerasifera Ⅰ and Prunus cerasifera Ⅱ(4.53-4.72 mg/g),and Cu content was higher in Magnolia denudate(22.74 μg/g),Zn content was higher in Prunus cerasifera Ⅱ(249.06 μg/g),Fe content was higher in Cercis chinensis,Cerasus sp.,Prunus cerasifera Ⅱ,Prunus mume,Malus spectabilis and Amygdalus persica(85.81-118.34 μg/g),Mn content was higher in Prunus mume,Cerasus sp.,Amygdalus persica and Malus spectabilis(24.09-25.71 μg/g).The falling flowers with faster release of N include Cerasus sp.,Malus spectabilis,Magnolia denudate,Magnolia liliflora,Amygdalus persica,Prunus cerasifera Ⅰ,Prunus cerasifera Ⅱ,Michelia figo and Cercis chinensis(annual release rate is95.78%-99.99%),and the falling flowers with faster release of P include Cerasus sp.,Malus spectabilis,Magnolia denudate,Magnolia liliflora,Amygdalus persica,Prunus cerasifera Ⅱ,Cercis chinensis,Ginkgo biloba and Koelreuteria paniculate(annual release rate is 91.81%-99.99%).The rapid release of K includes Magnolia denudate,Magnolia liliflora,Prunus cerasifera Ⅰ,Prunus cerasifera Ⅱ and Cercis chinensis(annual release rate is 90.79%-97.62%).Therefore,Magnolia denudata and Amygdalus persica were more suitable for the preparation of N and P fertilizers,and Magnolia denudata,Prunus cerasifera Ⅰ and Prunus cerasifera Ⅱ falling flowers were more suitable for the preparation of K fertilizer.(2)Except for the decomposition of Ginkgo biloba which is slightly slower(turnover period 1.12 a),among the 12 species of fallen flowers,the decomposition of other falling flowers is faster(turnover period 1.00—1.05 a year).In addition,the high content of crude protein,N,P and K in the falling flower matrix will accelerate the decomposition of the falling flower,while the higher lignin content in the falling flower,lignin/N and N/P will slow down the decomposition of the falling flower.(3)Among the falling flower extracts,those that showed a comprehensive effect of promotion on seed germination and seedling growth of Cucumis sativus were Cerasus sp.,Amygdalus persica,Prunus cerasifera Ⅰ,Prunus cerasifera Ⅱ,Michelia figo,Prunus mume,Koelreuteria paniculate and Armeniaca vulgaris,and those that showed a comprehensive effect of inhibition were Malus spectabilis,Magnolia liliflora,Cercis chinensis,Ginkgo biloba and Forsythia suspense.The comprehensive effect on Sorghum vulgare seed germination and seedling growth was promoted by Cerasus sp.,Malus spectabilis,Amygdalus persica,Prunus cerasifera Ⅰ,Prunus mume,Koelreuteria paniculate and Forsythia suspense,and inhibited by Magnolia liliflora,Prunus cerasifera Ⅱ,Michelia figo,Cercis chinensis,Ginkgo biloba and Armeniaca vulgaris.The comprehensive effect on seed germination and seedling growth of Triticum aestivum was promoted by Cerasus sp.,Amygdalus persica,Prunus cerasifera Ⅰ,Michelia figo,Prunus mume,Koelreuteria paniculate and Armeniaca vulgaris,and inhibited by Malus spectabilis,Magnolia liliflora,Prunus cerasifera Ⅱ,Cercis chinensis,Ginkgo biloba and Forsythia suspense.The comprehensive effect on seed germination and seedling growth of Brassica campestris was promoted by Cerasus sp.,Amygdalus persica,Prunus cerasifera Ⅰ,Ginkgo biloba and Koelreuteria paniculate,and inhibited by Malus spectabilis,Magnolia liliflora,Prunus cerasifera Ⅱ,Michelia figo,Cercis chinensis,Prunus mume,Armeniaca vulgaris and Forsythia suspense.(4)The falling flower extracts of Cerasus sp.,Amygdalus persica,Prunus cerasifera Ⅰ,Koelreuteria paniculate and Prunus mume can produce comprehensive allelopathic promoting effects on at least three receptors,so they are recommended as the most promising tree species for preparing biomass organic fertilizer.On the contrary,the extracts of falling flowers of Magnolia liliflora,Cercis chinensis,Malus spectabilis,Forsythia suspense,Prunus cerasifera Ⅱ and Ginkgo biloba can have a comprehensive allelopathic inhibitory effect on at least three receptors,so they are not suitable as base fertilizer and seedling application when used as fertilizer material in farmland,but can be considered for use as top dressing.