沼渣施用对土壤线虫群落结构的影响

为了解沼渣施用对土壤生物环境的影响,以土壤线虫为指示工具,通过盆栽试验对比沼渣(BR)、有机肥(OR)、化肥(CF)和不施肥(CK)4个处理下土壤线虫群落结构,评估不同施肥对土壤健康的影响,结果表明:沼渣可极大地刺激r-策略线虫的增长,使得线虫总数高出其他处理。各处理共获得线虫22个属,以食细菌线虫的种类和比例最高,然而不同处理食细菌线虫功能群的组成差异较大,沼渣处理几乎全部为cp值为1的小杆科线虫,有机处理cp1和cp2线虫比例相当,化肥和对照处理则主要是cp2的线虫。植食性线虫在沼渣处理中受到了明显的抑制。利用线虫群落评价不同施肥后的土壤状况,发现施用沼渣的土壤最优,食物网呈结构化,土壤养分富集;而化肥和不施肥对照土壤则表现出一定胁迫的状态。

Effects of biogas residue application on soil nematode community structure

To identify the effects of biogas residue application on the soil environment,we carried out a pot experiment of four treatments.Which were BR (biogas residue),OR (organic fertilizer),CF (chemical fertilizer) and CK (unfertilized) was conducted.The structure of soil nematode community was analyzed to evaluate the effect of the different fertilizer applications on soil health.Nematodes were classified into four trophic groups:bacterivores,fungivores,plant parasites and omnivore-predators.Nematode ecological indices were used to evaluate soil quality and food webs.These included a maturity index for nematodes with cp2-5 (MI2-5),enrichment index (EI),structure index (SI) and basal index (BI),which were calculated using the online NINJA program.The ratio of fungivores to bacterivores (FB),and the ratio of omnivore-predators to plant parasites (OPPP) were also calculated.The Shannon index (H'') and genus dominance (D) were also computed to describe nematode diversity.The results showed biogas residue stimulated populations of enrichment opportunists.The number of nematode found in this treatment was higher than in other treatments.A total of 22 genera were recorded,and bacterivores were dominant in all treatments.However,the composition of bacterivores differed among treatments.Most nematodes observed in BR were cp1 guilds (Rhabditidae),while the proportion of cp1 and cp2 nematodes were approximately equal in OR.In both CF and CK soils,cp2 guilds were the most dominant bacterivores.The relative abundance of omnivore-predators was significantly higher in OR treatments compared with other treatments (P<0.05).Biogas residue application suppressed plant feeders,compared with OR,CF and CK treatments.The maturity index for nematodes with cp2-5 (MI2-5),basal index and fauna analysis consistently showed that adding biogas residue to soil formed the healthiest soil environment compared with other treatments,with a structured soil food web and enriched soil condition.Chemical fertilizer and unfertilized treatments presented stressed soil conditions.The FB index indicated all treatments were bacteria-based decomposition.The OPPP index suggested a stronger control of predatory nematodes on herbivorous nematodes in BR soils compared with CF and CK soils (P<0.05).No significant correlation was found between two soil properties (available potassium and electrical conductivity) and nematode indices (P>0.05).Soil organic matter,total nitrogen and available phosphorus were significantly correlated with most of the nematode indices (P<0.05 or P<0.01).In general,MI2-5,EI and SI indices were positively correlated with soil nutrient content (P<0.05 or P<0.01),while BI and FB indices were negatively correlated (P<0.05 or P<0.01).In conclusion,the results obtained in this study suggested that application of biogas residue was a better option for soil health,at least in the short-term.It is found that biogas residue had potential ability to suppress plant parasites.However,the mechanisms and regulations of this topic need further study.