Allelopathy And Ecological Effect Of Poplar Root Exudates

Poplar plantantions in Dashahe Forest Farm, Feng County, Xuzhou city were selected tostudy. Allelopathic effects of poplar on soil enzyme, microorganism and nutrients were explored.The influence of aqueous extract from rhizosphere soil of poplar on lettuce, wheat and cornseeds were tested to explore the allelopathic effects of poplar plantation on crop growth. Resultsshowed that:1. Soil nutrients were enriched in the rhizospheric mini-field of poplar and the positiveallelopathic effect intensity of effective phosphorus was highest. The activity of urease, sucrase,alkaline phosphatase and catalase in rhizosphere soil was higher than that in non-rhizospheresoil and woodland soil. Polyphenol oxidase activity had the inverse rules. The positiveallelopathy on soil sucrase and alkaline phosphatase was stronger, while the negativeallelopathy on polyphenol oxidase was strongest. The amount of microorganisms in therhizosphere was higher than that in non-rhizosphere and woodland soil. The amount of bacteriawas largest. The allelopathy of root exudates of poplar on microorganisms was positive, and itwas strongest on fungi. Soil biological activity had obvious seasonal characteristics. Thecorrelation of soil nutrient with enzyme activity and microorganism was close.2. Continuous cropping of poplar caused a deterioration of soil physical properties and agenerational decline of nutrient content and the pH value. With the increasing generation ofpoplar, the activity of soil urease, catalase and alkaline phosphatase decreased, while soilpolyphenol oxidase activity had the inverse rules. The total amount of microorganismsdecreased with genenrational ascent.The proportion of actinomycetes in microbial componentshad a gradrually increasing trend, but bacteria and fungi had the inverse rules. After differenttree species grown in rotation, thre degree of soil physical property deterioration decreased, soilnutrient consumption and the acidification of soil were reduced, the positive allelopathic effecton soil urease and sucrase strengthened, the total amount of microorganisms was improved.3. Poplar Zhong he1was better than poplar I-72in the soil physical propertiesimprovement, and it may consume more phosphorus and potassium while poplar I-72mayconsume more nitrogen. Its soil acidification strength was less than poplar I-72. Overall, theactivities of soil urease, sucrase, catalase, of poplar Zhong he1rhizosphere were higher thanthem of poplar I-72rhizosphere, soil alkaline phosphatase and polyphenol oxidase had theinverse rules.But the positive allelopathy of poplar I-72on soil enzyme was stronger thanpoplar Zhong he1. The microorganisms were more active in the rhizospheric mini-field ofpoplar I-72.4. The aqueous extract from rhizosphere soil of poplar at low concentration, it promoted crop growth, while at high concentration it inhibited crop growth. The comprehensiveallelopathic effect of poplar root exudates on crop growth enhanced with genenrational ascent,weaked after different tree species grown in rotation. The adverse effects of poplar I-72on seedgermination, seedling bud and root growth was weaker than that of poplar Zhong he No.1.Poplar I-72was more suitable for agroforestry system.