根结线虫病土引入秸秆碳源对土壤微生物群落结构的影响

Effect of adding wheat straw carbon source to root knot nematode diseased soil on soil microorganism community

【目的】微生物生物量及群落结构对农业管理措施极为敏感,土壤微生物数量和多样性的大小是土壤肥力状况的重要生物学指标,秸秆还田影响着土壤微生物的种群和数量。由于不合理的耕作,引起严重的根结线病虫害,尤以连作的番茄土壤十分普遍,研究连作条件下添加秸秆碳源对根结线虫(Meloidogyne spp.)病害严重土壤中土壤微生物生物量和群落结构的影响,探讨添加秸秆碳源加入量与土壤微生物量、群落结构及其真菌/细菌比值的相互关系、变化规律,可为病土的生态修复奠定一定的理论基础。【方法】本试验采用室内盆栽方法,试验设置4个小麦秸秆添加量0、2.08、4.16和8.32 g/kg,分别记为S0、S1、S2和S3,供试作物为番茄。采用磷脂脂肪酸法(PLFA)估算真菌生物量、细菌生物量和微生物生物总量。【结果】与不加秸秆的对照相比,秸秆碳源的施入显著增加了土壤微生物总生物量(MTB)、细菌生物量(MB)、真菌生物量(FB)。S3、S2和S1处理的MTB、MB、FB分别为30.17、28.42和22.72 nmol/g;24.27、23.12和22.97 nmol/g;5.90、5.30和4.93 nmol/g;不同秸秆添加量处理之间,微生物总生物量和细菌生物量之间差异不显著,但真菌生物量差异达显著水平。添加秸秆处理使土壤中微生物群落结构发生了变化,真菌/总生物量(FB/MTB)、真菌/细菌(F/B)比值显著提高。S3、S2和S1处理的FB/MTB和F/B分别为19.56%、18.65%和17.78%;24.34%、22.94%和21.68%;S3和S2的比值之间差异不显著,两个处理的比值与S1处理之间差异显著。秸秆的添加对细菌生物量在微生物总量中的比例有降低作用,细菌在微生物总量中占据绝大比例,在S0、S1、S2、S3个处理中分别为83.10%、82.22%、81.35%和80.44%,F/B比值分别为20.30%、21.68%、22.94%和24.34%。【结论】随着秸秆施入量的的增加,微生物总生物量、细菌和真菌生物量和F/B比值均有升高的趋势,特别是有利于F/B比值增加,说明秸秆碳源的施入改变F/B比值,从而改善病土食物网结构和土壤生态系统食物网营养结构。秸秆添加量以4.16和8.32 g/kg更为有效。

Objectives Microbial biomass and the microbial structure are very sensitive to the agricultural practices. The population of microbial biomass and its diversity in structure are important index for soil fertility, the straw returned to field affects species and quantity of soil microorganisms. Severe root-knot nematode disease often arises due to unreasonable agricultural practices, especially in the continuous cropping fields of tomato. The effect of adding straws into soil on the microbial structure and diversity and the ratio of fungus to bacteria ( F/B) of mutual relations and change rule were studied to provide a way of biological remediation for the soils suffered with root knot nematode disease. [Methods]A pot experiment using soils from successive planting of tomato and suffering from serious root knot nematode disease was conducted with a root knot nematode sensitive tomato cultivar as a tested crop. Four gradient amounts of wheat straw were designed:0 ( S0 ) , 2. 08 g/kg ( S1 ) , 4. 16 g/kg ( S2 ) and 8. 32 g/kg ( S3 ) in the experiment. The fungal biomass, bacterial biomass and microbial biomass were detected with the method of phospholipid fatty acid ( PLFA ) . [Results]Compared with control, adding wheat straw significantly increases the amounts of total soil microbial biomass ( MTB) , bacterial biomass ( MB) and fungal biomass ( FB);increases the ratios of fungal biomass to total soil microbial biomass ( FB/MTB ) , the ratio of fungus to bacteria (F/B). The MTB, MB, FB of S3, S2 and S1 are 30. 17, 28. 42 and 22. 72 nmol/g, 24. 27, 23. 12 and 22. 97 nmol/g, 5. 90, 5. 30 and 4. 93 nmol/g, respectively. There is no significant difference in MTB and MB among the three adding treatments, but the FB of S3 is significantly higher than those of S1 and S2. The proportions of MB in soil MTB are also reduced significantly under the straw addition, and the MB possess is an overwhelming proportion in soil MTB. The average proportions of MTB are 83. 10%, 82. 22%, 81. 35% and 80. 44%, and F/B ratios are 20. 30%, 21. 68%, 22. 94% and 24. 34% in the S0 , S1 , S2 and S3 treatments, respectively. [Conclusions]Adding wheat straw can improve the total microbial biomass, the bacteria biomass and the fugal biomass. the ratio of fungi population to the total microbial and to the bacteria are all increased significantly. Therefore, adding wheat straw is an effective way of remediate the biological diversity and ressistance to the root knot nematode disease. When the adding amount of the straw is 4. 16 and 8. 32 g/kg, the effect is more signifiant.