蚯蚓菌根互作对土壤酶活、甘薯根系生长及养分吸收的影响

Effect of earthworm-mycorrhiza interaction on soil enzyme activities,root growth and nutrients uptake of sweet potato

【目的】蚯蚓和丛枝菌根真菌处于不同的营养级,但在促进植物生长和提高土壤肥力等方面却都发挥着积极作用。单独对土壤微生物或土壤动物的研究较多,但对土壤微生物与土壤动物之间相互作用的研究很少。因此研究它们对土壤和植物生长的作用可为挖掘土壤生物的潜力和提高土壤生物肥力提供依据。【方法】采用盆栽试验,研究了蚯蚓(Eisenia fetida)与丛枝菌根真菌(Rhizophagus irregularis)互作对甘薯生长和养分吸收的影响。试验采用两因素完全随机试验设计,分为接种和不接种菌根真菌及添加和不添加蚯蚓。试验共4个处理:不加菌根和蚯蚓(CK);接种菌根真菌(AM);添加蚯蚓(E);添加蚯蚓和菌根真菌(E+AM),每个处理4次重复。调查了甘薯养分吸收、根系形态及土壤养分变化,采用Canoco4.5软件对土壤生物与植物对应关系进行RDA(redundancy analysis)分析。【结果】接种菌根真菌显著提高了甘薯地上和地下部生物量(P<0.05),而添加蚯蚓的处理仅提高了甘薯地上部生物量。同时添加蚯蚓和菌根的处理显著提高了甘薯地上地下部生物量,并且高于其他三个处理(P<0.05)。与对照相比,接种菌根真菌显著提高了土壤磷酸酶活性(P<0.01),增幅近一倍;同时提高了土壤磷的植物有效性,土壤有效磷含量下降了30%左右。添加蚯蚓后土壤脲酶活性从5.45 mg NH+4-N/g显著增加到8.71mg NH+4-N/g,土壤碱解氮的含量从5.82 mg/kg显著增加到6.89 mg/kg(P<0.05)。RDA分析表明蚯蚓菌根互作对甘薯地上和地下部氮磷含量、根表面积、根体积、根平均直径和根尖数均存在显著的正交互效应。蚯蚓菌根互作通过调控土壤酶和改变土壤养分有效性促进甘薯对土壤氮磷养分的吸收。【结论】蚯蚓(Eisenia fetida)通过调控土壤脲酶和碱性磷酸酶增加了土壤中氮磷的有效性从而促进甘薯地上部生长。丛枝菌根真菌(Rhizophagus irregularis)通过调控土壤磷酸酶和增加植株地上地下部吸磷量从而促进甘薯生长。添加蚯蚓或接种菌根真菌均能增加根系吸收面积和根体积从而促进甘薯对养分的吸收。蚯蚓和菌根真菌相互作用通过调控土壤酶和改变土壤养分有效性以及促进根系发育从而互补的促进甘薯养分吸收和生长。

【Objectives】Earthworms and arbuscular mycorrhizal fungi are in different trophic levels in food chain,but they play similar roles in promoting plant growth and soil biological fertility. Most researches have been focused on particular group of soil organisms,ferwer on underground interactions and functional diversities of various soil microorganisms as well as on soil macrofauna. Investigations in these fields are necessary to explore the potentiality of soil organisms for sustainable development of agriculture. 【Methods 】A pot experiment was conducted using sweet potato as test materials in a greenhouse. A completely randomized block design with a 2 × 2 factorial arrangement of treatments was established. The two factors,AM fungi and earthworms were used,and each factor has two levels. The detail treatments include： Neither earthworm nor mycorrhizae addition（ CK）,earthwormaddition（ E）,mycorrhizal addition（ AM）,and both earthworms and mycorrhizae addition（ AM ＋ E）. The growth and nutrient uptake of sweet potato,and the availability of soil nutrients were investigated. The relationships between treatments were tested by Pearson＇s correlation analyses. The redundancy analysis（ RDA） was performed by using the Canoco version 4. 5 software package to describe the relationship between soil fauna and flora.【Results】AM fungi increased sweet potato shoot and root biomass; addition of earthworms alone significantly（ P〈0. 05） increased sweet potato shoot biomass. The AM ＋ E treatment significantly improved sweet potato growth and higher than other three treatments（ P〈0. 05）. Inoculation with AM fungi significantly（ P〈0. 01） increased the activity of soil alkaline phosphatase,but decreased the concentrations of available phosphorus in soil at harvest stage. Addition of earthworms significantly increased the activity of soil urease（ from 5. 45 to 8. 71 mg NH＋4-N / g）and soil ammonium-N concentrations（ from 5. 82 to 6. 89 mg / kg）（ P〈0. 05）. AM fungi increased sweet potato shoot weight and root P content,while earthworms improved N and P contents in shoots. The RDA analysis showed that AM fungi and earthworm exist significant positive interaction effects on shoot and root nitrogen and phosphorus contents,root surface area,root volume,root diameter and root tips. Interaction between AM fungi and earthworm increased sweet potato shoot and root biomass through the pathway regulating soil enzyme activities and N and P availabilities.【Conclusions】This study sheds light on the possibility to improve plant nutrient uptake by regulating soil biological processes with earthworms and arbuscular mycorrhizal fungi,indicating that the potential for soil biological fertility in the sustainable agricultural system could be realized by utilization earthworms and arbuscular mycorrhizal fungi.