蚯蚓菌根互作促进甘薯吸收利用氮磷养分的作用机理

Soil biological fertility is one of the important features of soil fertility. It is characterized by the active life process of soil microbes,soil animals and plants roots and it is good for the growth,reproduce and superior quality of the plants.Earthworm and Arbuscular mycorrhizal fungus are both among the beneficial soil biota. They play important roles in nutrient availability in soil and to plant.The interactive impacts of arbuscular mycorrhizal fungi and earthworms on sweet potato growth and nutrient uptake were studied under greenhouse condition and natural conditions with in field. The main contents included: Root colonization, mycorrhiza structure, plant biomass and N and P contents of shoots and roots, soil available P and N concentrations, and soil microbial biomass C and N were measured. The isotope tracer technique and the PLFA method were used to clarify the mechanism of sweet potato straw decomposition and plant N uptake by interacting earthworms and AMF. We also study that earthworms and mycorrhizal fungi interactions improve soil phosphorus bioavailability and space availability. We conducted a split plot in randomized complete block design inoculated or not inoculated with AMF, treated or not treated with earthworms. We used concrete frames inserted vertically into field around the relevant plots to prevent earthworms from escaping. We inoculated with AM fungi in paper bags and then hand transplanted them into the field. Researchs shed light on the possibility to improve plant nutrient uptake by regulating biology, which could explore the potential for soil biological fertility in the sustainable agricultural system.

土壤肥力的维持与提高是农业可持续发展的关键环节之一。提高土壤肥力除了传统的物理和化学措施之外，土壤生物特别是蚯蚓和丛枝菌根真菌具有潜在的重要作用，但其相互作用对提高土壤养分有效性及促进作物生长的机制尚缺乏深入研究。本研究以土壤生物互作为切入点，采用自行改制的空气隔层分室装置结合同位素15N、33P示踪手段，分别在根际和菌丝际研究蚯蚓菌根互作对甘薯吸收氮、磷的作用机理，初步揭示蚯蚓菌根互作对氮素吸收的可控性及蚯蚓菌根互作提高土壤磷素生物有效性和空间有效性的规律。在室内试验的基础上进行田间验证，构建薯蔓秸秆行间还田模式，采用纸袋法接种菌根及围栏法田间投放蚯蚓，研究田间条件下生物互作对甘薯生长和养分吸收的影响以及这些影响对甘薯生长的反馈作用。研究工作将在理论上探索蚯蚓菌根协同互补的机制，在实践上为提升土壤生物肥力及促进农业的可持续发展提供科学依据。

蚯蚓和丛枝菌根真菌处于不同的营养级，但在促进甘薯生长和提高土壤生物肥力等方面却都发挥着积极作用。本研究采用田间试验和室内试验相结合的方法，研究了蚯蚓菌根互作及其对甘薯氮、磷养分吸收、产量形成和土壤微生物群落多样性的影响。主要结果如下：(1)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。(2)蚯蚓能增加薯蔓秸秆15N的矿化，但不能够直接影响15N向甘薯的传递。菌根菌丝能够吸收薯蔓秸秆的氮素并传递给寄主植物。通过蚯蚓活化-菌根传递的方式，蚯蚓菌根互作促进了甘薯对薯蔓中氮素的吸收利用。(3)在低磷和中磷水平下，接菌AM真菌显著提高了甘薯的净光合速率、气孔导度和蒸腾速率；甘薯叶片中蔗糖合成酶、6-磷酸葡萄糖酸脱氢酶、蔗糖磷酸合成酶和磷酸酶活性也显著提高。中等磷水平下，添加蚯蚓对于提高土壤磷活化及甘薯磷素有效性效果显著高于低磷和高磷水平。说明接种菌根和蚯蚓的效果受土壤磷水平的影响。(4)在田间条件下，添加蚯蚓和接种菌根都能显著提高甘薯产量。蚯蚓通过取食秸秆释放养分并提高土壤养分的有效性，最终增加玉米产量。菌根主要通过增加土壤磷酸酶活性，提高土壤磷的有效性，并促进甘薯对土壤磷的吸收。添加蚯蚓或接种菌根对土著土壤中细菌和真菌群落结构及多样性的影响年际间变化不同。蚯蚓菌根互作通过对土壤微生物群落结构的影响提高了植株对养分的吸收进而促进的产量的增加。项目资助发表学术论文5篇，申请国家发明专利3项。项目投入经费25万元，支出19.48万元，各项支出基本与预算相符，剩余经费计划用于本项目研究后续支出。