菌根与根瘤菌联合应用对复垦矿区根际土壤环境的改良后效

Lasting improvement effects of arbuscular mycorrhizal fungi and Bradyrhizobium japonicum on rhizosphere soil environment in mining subsidence

为了进一步确定微生物复垦对土壤的持续修复能力,在神东矿区活鸡兔开采沉陷试验基地,接种丛枝菌根真菌和大豆根瘤菌改良农用地土壤,已取得了较好的微生物复垦效果,经过2a的退耕撂荒以后,对微生物复垦后效进行系统地研究。研究结果表明,撂荒后,接菌小区根外菌丝密度、根系侵染率和pH值均显著高于对照小区,分别比对照提高了90%、52%和1.3%;接菌小区细菌数量、微生物总量、有效磷含量、电导率和酸性磷酸酶活性也明显高于对照小区,但差异不显著。撂荒后与撂荒前相比,土壤呈退化趋势,但接菌小区菌丝密度几乎增加了1倍,差异显著,同时侵染率、细菌数量和酸性磷酸酶活性均明显升高,差异不显著;而在对照小区中,菌丝密度稍有增加,侵染率、细菌数量和酸性磷酸酶活性均明显降低,且差异不显著。利用丛枝菌根真菌与大豆根瘤菌联合作为绿色环保肥料,能够有效改善根际土壤环境,减轻土壤的退化程度,在弃耕状态下也能发挥良好的效用,对土地贫瘠的开采沉陷地进行生态修复具有重大意义。

In a mining subsidence experiment in the Shendong mining area in the Shaanxi province of China, agricultural soil was improved by inoculation with arbuscular mycorrhizal fungi and Bradyrhizobium japonicum. This experiment was implemented in mid-May 2008 for the first planting, and in the end of April 2009 for the second time. It was divided into two experiment plots, inoculated and control. After two years of abandoned cropland, in September 2011, 15 random positions were selected under the ＂S＂ shape method from each district, and roots and fresh rhizosphere soil samples were collected. The aftereffect of microbial reclamation of the soil was studied systematically, about which there have been no reports until now. The results were 1） the density of external hyphal of the inoculation treatment was 5.58 m/g, 90% higher than the control after abandonment, the difference reaching a significant level, and it was also significantly higher than the two sets of processing before abandonment; 2） the root infection rate of the inoculation treatment was 91%, 52% higher than the control after abandonment, the difference reaching a significant level, and it was significantly higher than the control before abandonment; 3） pH value of the inoculation treatment was significantly higher than that of the control after abandonment; 4） in the inoculation treatment the number of bacteria, microbial total, available phosphorus content, conductivity and acid phosphatase activity were also greater than that of the control after abandonment, the differences not reaching a significant level; 5）compared with before and after abandonment, the soil was in degraded trends; in a comparison between the years of 2009 and 2011, in the control treatment there was a slight increase in hyphal density, the difference not reaching a significant level, while in the inoculation treatment hyphal density was twice than that before abandonment, the difference reaching a significant level; 6）compared with before and after abandonment, the root infection rate, the number of bacteria and acid phosphatase activity were increased in the inoculated treatment, while that of the control was decreased. The results showed that abandoned cropland did not affect the soil mycelium growth and development, and compared with before and after abandonment mycelial density improved greatly; the root infection potential was improved in the inoculated treatment as observed through a microscope; and total soil microbes were increased. These consequences confirmed the advantages of artificial inoculation, affecting the number of rhizosphere microorganisms and the formation of the dominant flora, and increasing microbial activity and species diversity. There was evidence to show that the microbial diversity determined plant biodiversity and ecosystem stability and productivity. Soil acid phosphatase activity was enhanced by inoculation, and the soil available phosphorus content was very scarce; when phosphorus is the main limiting factor for soil microbes and plant growth, microorganisms and plant roots secrete extracellular acidic or alkaline phosphatase enzymes, hydrolyzing organic phosphorus, phosphorus-containing organic compounds into simple inorganic compounds that the plant can absorb. Arbuscular mycorrhizal fungi as a green manure can be effective long-term on soil improvement, without disturbing the soil, but is conducive to the development of the mycelium, having important significance for microbial reclamation of mine subsidence. Arbuscular mycorrhizal fungi and Bradyrhizobium japonicum combined can effectively improve the rhizosphere soil environment, enhance natural succession, and is of great significance to ecological restoration of barren land resulting from mining subsidence.