水肥耦合对香蕉园土壤线虫群落结构及多样性的影响

Effect of different water and fertilizer coupling on soil nematode community structure and diversity in banana plantation

以海南香蕉种植区为例,研究了水肥一体化条件下,不同水肥用量(低肥:每株香蕉施尿素400 g、磷酸二氢钾256 g、氯化钾1 024 g;高肥:每株香蕉施尿素500 g、磷酸二氢钾320 g、氯化钾1 280 g;低水:3 800 L/株,高水:4 750 L/株)对土壤线虫群落结构及多样性的影响。4个取样时期低肥低水(A)、低肥高水(B)、高肥低水(C)和高肥高水(D)4个处理的线虫总数、食细菌线虫数量、食真菌线虫数量、植物寄生线虫数量和捕食/杂食线虫数量均存在显著差异(P<0.01)。本试验田中共鉴定出土壤线虫22科34属,其中巴兹尔属(Basiria)和针属(Paratylenchus)为优势属。单增加施肥量显著增加了植物寄生线虫数量和捕食/杂食线虫数量,同时增加施肥量和灌水量显著增加了线虫总数、食细菌线虫数量和食真菌线虫数量。从整个生育期来看,线虫总数和4个线虫营养类群的数量在苗期均较低,抽蕾期和成熟期均较高。4个取样时期A、B、C和D4个处理的多样性指数(Shannon diversity,H)、自由生活线虫成熟度指数(Maturity index,MI)、通道指数(Channel ratio,NCR)、Wasilewska指数(Wasilewska index,WI)和富集指数(Enrichment index,EI)均存在显著差异(P<0.01)。单增加灌水量显著增加了结构指数(Structure index,SI)和EI指数,单增加施肥量显著增加了H和NCR指数,同时增加施肥量和灌水量显著增加了植物寄生线虫成熟度指数(plant parasite index,PPI)。从整个生育期来看,苗期的H、NCR、SI和EI指数较高,营养生长期的MI和WI指数较高,抽蕾期的优势度指数(dominance index,λ)较高,成熟期的PPI指数较高。该研究结果表明,土壤线虫群落结构的变化很好地反映土壤水肥的变化状况,土壤线虫可作为施肥和灌溉过程中土壤质量变化的生物学指标。

Soil nematodes are the most abundant group of soil animals that rapidly react to environmental changes. In the farmland ecosystem, fertilizer and irrigation are two important factors influence the composition and diversity of soil nematode community. The effect of various water and fertilizer usages under a fertigation regime on the soil nematode community structure was investigated in a banana plantation of Hainan Province in this study. Four treatments were designed： A（low amount of water and fertilizer）, B（low amount of fertilizer and high amount of water）, C（high amount of fertilizer and low amount of water）, and D（high amount of water and fertilizer）. Soil samples were extracted using a soil corer（3.0 cm diameter） at a depth of 0-30 cm below the soil surface from July 2011 to June 2012 within the plant rows of banana plants, 50 cm from the base of the banana plant. The nematodes were extracted through the shallow basin method, and were identified to the genus level with the aid of a microscope. Results showed that significant treatment effects（P0.01） were observed in the abundance of total nematodes, bacterivores, fungivores, plant parasites, omnivore-predators, the values of diversity（H）, maturity index（MI）, channel ratio（NCR）, the wasilewska index（WI）, and the enrichment index（EI） during the four sampling stages. Thirty-four nematode genera belonging to twenty-two families were identified during the sampling stages, of which Basiria and Paratylenchus were the dominant genera. The abundance of plant parasites and omnivore-predators in the C treatment and the abundance of total nematodes, bacterivores, and fungivores in the D treatment were significantly higher than in the other treatments. The values of MI and WI in the A treatment, the values of structure index（SI） and EI in the B treatment, the values of H and NCR in the C treatment, and the values of thheplant parasite index（PPI） in the D treatment were significantly higher than in the other treatments. Significant sampling time effects（P 0.01） were observed in the abundance of total nematodes, bacterivores, fungivores, plant parasites, the values of H, dominance（λ）, PPI, NCR, WI, SI, and EI. The abundance of bacterivores, fungivores, and plant parasites at the booting and ripening stages were significantly higher than at the other stages. The values of H, NCR, SI, and EI at the seedling stage, the values of MI and WI at the jointing stage, the values of λ at the booting stage, and the values of PPI at the ripening stage were significantly higher than at the other stages. The analysis of NCR showed that bacterial decomposition was the major decomposition pathway in the soil organic substance decomposition system. The data from MI, PPI, SI, and EI demonstrated that the nematode community structure was more stable in the A and B treatments than in the C and D treatments. The excessive application of water and fertilizer increased the level of disturbance of the soil ecosystem and posed a significant threat to the soil environment. Nematodes could be used as bio-indicators for assessing soil quality under irrigation and fertilization.