绿肥接种AM真菌促进后作番茄菌根侵染及氮磷转化吸收的机理研究

Arbuscular mycorrhizal(AM) can improve the growth of plants through increased uptake of available soil phosphorus (P) and other non-labile mineral nutrients essential for plant growth, they have also 'non-nutritional' effects in stabilising soil aggregates, in preventing erosion, and in alleviating plant stress caused by biotic and abiotic factors. The beneficial effects of AM fungi on plant performance and soil health are essential for the sustainable management of agricultural ecosystems. As biological fertilizers, AMF has broad application prospects. But because of the instability of AMF fertilizer in agricultural production, its utilization is limited to nursery in horticulture and forestry. Studies on crop rotation have suggested that the cultivation of mycorrhizal host crops increases the AMF colonization of succeeding crops. According to our preliminary studies, as preceding crop, AM-host green manure pre-inoculated with AMF, had a positive effect on reducing fertilizer application of succeeding vegetable production. Therefore, in order to get approaches of improving the stability of AMF inoculum in the field and explore its mechanism, a serial of experiments would be conducted to determine the positive effect of AM-host green manure on the growth, AM colonization and N, P uptake of succeeding tomato. Through soil incubation, pot experiments and isotope tracer, we measure the arbuscular mycorrhizal fungal colonization, external mycelium length, and spore numbers, microbial community composition in the soil, and explore the flux and transformation of carbon, nitrogen and phosphorus in the system of green manure - mycelium - plants. Our aims are to elaborate the mechanisms of green manure pre-inoculated with AM fungi improving AMF colonization, nitrogen and phosphorus transformation and uptake of succeeding tomato, reduce the inputs of nitrogen and phosphorus in vegetable production, and gain the practical method of improving the stability of AM fungi in the field.

丛枝菌根（AM）在增强植物对矿质元素吸收、提高植物抗逆和抗病性、改善土壤结构及水分保持等方面具有重要的作用。但由于AM真菌的活体营养特性，且在大田生产中的应用效果不稳定，限制了其推广。根据我们的前期研究，以AM真菌易于侵染的绿肥作前作物，预接种AMF在蔬菜减量施肥中有较好的效果。因此，本项目拟通过一系列盆栽试验、土壤培养和三室根箱同位素示踪方法，采用AMF易于侵染的绿肥植物作为接种材料，预接种AM菌剂，促进AM真菌大量繁殖，然后种植后茬作物番茄，测定植物根系AM侵染率，土壤中AM真菌的菌丝量和孢子数、微生物群落组成、酶活性变化和氮磷有效性变化，碳、氮和磷在绿肥-菌丝体-植物之间的迁移转化，研究种植绿肥预接种AM真菌提高后茬番茄AM真菌接种效应、加强土壤中氮磷转化及促进番茄氮磷吸收的机理，并就盆栽试验结果进行田间小区验证，以达到提高AMF田间应用稳定性、降低蔬菜作物生产中氮磷肥投入的目的。

丛枝菌根真菌（AMF）可以增强植物对矿质元素的吸收，提高植物抗逆和抗病性，改善土壤结构并加强土壤的水分保持。但AM真菌在大田生产中的应用效果不稳定，限制了其推广。本项目在筛选适宜菌根侵染的绿肥品种、确定适宜的接种量和接种方式的基础上，以AM真菌易于侵染的绿肥作前作物，预接种AMF研究一些生产措施在促进植物根系菌根真菌的侵染及蔬菜减量施肥中的效果，并探究其机理。研究结果发现，绿肥作前作物并预接种AMF菌剂可以显著促进后作青椒的生长及氮磷的吸收，其机理在于前作的绿肥可以显著提高土壤中孢子数，增加后作青椒根系的侵染率，扩大其根系对土壤矿质营养的吸收范围；尤其在缺磷土壤上，绿肥预接种AMF菌剂可以显著提高土壤中的真菌拷贝数，促进青椒对磷的吸收，缓解其缺磷症状。不种植绿肥而是添加外源碳（葡萄糖和蔗糖）以提供微生物食物，也可提高接种AMF的番茄根系侵染率、土壤孢子数和地上部生物量以及磷、钾吸收量。鉴于绿肥促进土著AMF扩繁的实验效果不显著，显著低于预接种AMF绿肥的处理，为探究土著微生物对青椒生长的影响，通过盆栽实验设置不同氮磷水平和灭菌与不灭菌处理，探讨土壤微生物在青椒利用土壤氮磷养分中的作用，发现黄棕壤灭菌后，青椒生长受到极显著的抑制；而潮土种植的青椒生长不仅没有受到灭菌的影响，反而灭菌有促进其生长的趋势，尤其是在N供应不足（N0P0）时灭菌显著地促进青椒生长，潮土灭菌促进青椒对氮、磷的吸收，而黄棕壤灭菌后极显著地抑制作物对氮、磷的吸收，灭菌后的土壤中微生物生物量碳的变化趋势与青椒生长一致。