The Impact Of Arbuscular Mycorrhiza Fungi On Soil Structure Characters

The possible use of arbuscular mycorrhizal fungus (AMF) for ameliorate soil structure was suggested considering increasing soil fertility and meeting the need of more crop yield which was based AMF can form symbiosis with most crop plants. The influence of mycorrhizal inoculation on soil aggregate quantity and water stable aggregate was detected and then root split device with two or four compartments was used to investigate the mechanism of plant, AMF and soil organic matter on soil structure which was quantitative analysis with path analysis. The main results as followed.(1)The pot experiment was carried with Triticum aestivuml (wheat) as host plants and two different arbuscular mycorrhizal fungus, Glomus intraradices and G. mosseae were inoculated under two phosphorus supplied level. After harvest, soil were screened through sieves with different sizes and then the amounts of different size of aggregates were measured to obtain geometric mean diameter (GMD), mean weight diameter(MWD) and fractal features of soils. The results showed that infection rates of root under no phosphorus supplied level were significantly higher than that under high phosphorus supplied level. Mycorrhizal inoculation didn't play a significant role on the root dry weight, but mycorrhizal inoculation increased soil organ matter concentration, total glomalin related soil protein (TG) concentration and the amount of water stable aggregate (WSA) significantly compared with the non-mycorrhizal treatments. Mean weight diameter (MWD) and geometric mean diameter (GMD) of mycorrhizal soil were significantly higher than that of non-mycorrhizal soil while mycorrhizal inoculation decreased the value of fractal dimension (D) of mycorrhizal soil compared with the non-mycorrhizal soil.(2) To investigate the impacts of AM fungi on soil aggregation dynamics in the neutral purple soil, split root device with two compartments was used and the soil were passed through sieves and then amounts of different size of aggregate were measured to obtain fractal features of soils. Path analysis was also used to evaluate the indirect or direct influencing factors. The results showed that inoculation with both G. intraradices and G. mosseae tends to increase the organic matter content and total glomalin related soil protein content in mycorrhizal soil. Mean weight diameter (MWD) and geometric mean diameter (GMD) with wet-sieving methods in mycorrhizal compartment were significantly higher than that of root compartment which resulted in the lower fractal features of mycorrhizal soil. All these results account for the important role of AM fungi in improving soil structure. The Path analysis results showed hyphae density had the highest index on WSA amount through direct effect mainly.(3)Split root device with four compartments was used to quantitatively compare the change of soil aggregate in mycorrhizosphere soil, rhizoshere soil, hyphosphere soil and bulk soil in our study. The results showed that there were a significant positive correlation between hyphae density, easy extractive glomalin (EEG) and mean weight diameter(MWD), geometric mean diameter (GMD) and the amount of larger macroaggregates (>250μm up to several millimeters diameter, R0.25).The correlation index between water stable aggregate and hyphae density in mycorrhizal soil and hyphae soil was 0.777,0.671 respectively. The GMD and MWD of R0.25 in hypahe compartment were higher than these in root compartment but were lower than these in mycorrhizal compartment which mean mycorrhizal hyphae had greater effect on formation and stabilization of soil aggregate than root but had less than mycorrhiza root primitively. The different ability of AM fungus to improve soil structure revealed the function diversity of AM fungi. More AM fungal species and soil types will be considered in our following studies.(4) Simulation field experiments showed that rotation destoried the growth of hyphae. Soil hyphae density under mesh static was significantly higher than that under mesh rotated and solid after inoculation with both G. intraradices and G. mosseae. Barrier treatment significantly impact the shoot dry weight,hyphae density, total glomalin related soil protein(TG), mean weight diameter (MWD), geometric mean diameter (GMD)and the amount of larger macroaggregates (>250μm up to several millimeters diameter, R0.25) in the soil.