Effects of different straw returning amounts and fertilizer conditions on bacteria of rice's different part in rare earth mining area.

Pot experiments were conducted to explore the effects of different rice straw returning soil on the community structure and function of bacteria in rice root, rhizosphere, leaf and phyllosphere under 7 conditions of rice straw combined with different fertilizers respectively. The results showed that: rice straw returning in different ways increased the content of soil pH and K, and reduced the accumulation of N, P and organic matter in soil, and different rice straw returning ways had different effects; rice straw returning reduced dry weight of rice grain, 2% of rice straw returning reduced rice grain greater than that of 1% rice straw returning; The reduction of NP combined fertilization is greater than that of NK combined fertilization and NPK combined fertilization. Except for the decrease of chao_1 index in rice root at maturity, rice straw returning significantly improved the abundance, diversity and evenness of bacteria in rice root, rhizosphere, leaf and phyllosphere. Rice straw returning increased the content of REEs in rice, and 2% of rice straw returning soil increased rare earth element (REE) content in rice grain greater than that of 1% rice straw returning soil. Different ways of rice straw returning soil reduced the abundance of Bacillus, while the abundance of Exiguobacterium in rice leaves was hundreds of times higher than that of the control group, and the genus in leaves was dozens of times higher than that of the control group, 2% of rice straw returning soil increased the abundance of harmful bacteria and pathogens of Acidovorax, Clostridium sensu stricto, Citrobacter, Curtobacterium, and 1% of rice straw returning soil promoted the abundance of nitrogen fixing bacteria, plant growth-promoting bacteria, stress resistant bacteria such as Lactobacillus, Azospira, Acinetobacter, Bradyrhizobium and Acidocella; Environmental factors such as available P, organic matter, total nitrogen, nitrate nitrogen, rare earth element content in rice roots, available K and soil moisture are important factors affecting the community structure of bacteria in rice roots, rhizosphere, leaf and phyllosphere at tillering stage of the rice. pH, REE content in rice roots, shoots, organic matter, total nitrogen, nitrate nitrogen and soil moisture content are the main environmental factors affecting the community structure of bacteria in rice roots, rhizosphere, leaf and phyllosphere at maturity stage of rice. 2% rice straw returning soil promoted the formation of harmful bacteria, which may be an important reason for its significant reduction in the dry weight of rice grains.

Effects of rare earth elements on bacteria in rhizosphere, root, phyllosphere and leaf of soil-rice ecosystem.

The effects of rare earth mining on rice biomass, rare earth element (REE) content and bacterial community structure was studied through pot experiment. The research shows that the REE content in rice roots, shoots and grains was significantly positive correlated with that in soil, and the dry weight of rice roots, shoots and grains was highly correlated with soil physical and chemical properties, nutrient elements and REE contents; The exploitation of rare earth minerals inhibited a-diversity of endophytic bacteria in rhizosphere, root, phyllosphere and leaf of rice, significantly reduced the abundance index, OTU number, Chao, Ace index and also significantly reduced the diversity index-Shannon index, and also reduced uniformity index: Pielou's evenness index, which caused ß-diversity of bacteria to be quite different. The exploitation of rare earth minerals reduces the diversity of bacteria, but forms dominant bacteria, such as Burkholderia, Bacillus, Buttiauxella, Acinetobacter, Bradyrhizobium, Candida koribacter, which can degrade the pollutants formed by exploitation of rare earth minerals, alleviate the compound pollution of rare earth and ammonia nitrogen, and also has the function of fixing nitrogen and resisting rare earth stress; The content of soil available phosphorus in no-mining area is lower, and the dominant bacteria of Pantoea formed in such soil, which has the function of improving soil phosphorus availability. Rare earth elements and physical and chemical properties of soil affect the community structure of bacteria in rhizosphere and phyllosphere of rice, promote the parallel movement of some bacteria in rhizosphere, root, phyllosphere and leaf of rice, promote the construction of community structure of bacteria in rhizosphere and phyllosphere of rice, give full play to the growth promoting function of Endophytes, and promote the growth of rice. The results showed that the exploitation of rare earth minerals has formed the dominant endophytic bacteria of rice and ensured the yield of rice in the mining area, however, the mining of mineral resources causes the compound pollution of rare earth and ammonia nitrogen, which makes REE content of rice in mining area significantly higher than that in non-mining area, and the excessive rare earth element may enter the human body through the food chain and affect human health, so the food security in the REE mining area deserves more attention.

Evaluation of several phosphate amendments on rare earth element concentrations in rice plant and soil solution by X-ray diffraction.

The exploitation and smelting of rare earth resources lead to serious pollution of rare earth elements (REEs) in farmland around mining area. The influence of four kinds of phosphate amendments-phosphate rock (PR), superphosphate (SSP), bone char (BC), and calcium magnesium phosphate (CMP)-on the bioavailability of REEs and the uptake and accumulation of 15 types of REE in rice were conducted in this study. Soil solutions were collected at tillering stage, heading stage and maturing stage, and rice was harvested at maturing stage. The mechanism of phosphate amendments reducing the bioavailability of REEs was studied by X-Ray diffraction and ICP-MS. PR treatment inhibited rice growth, but SSP, BC and CMP treatments all promoted rice growth, improved biomass of roots, shoots and grains, and promoted the uptake of phosphorous in rice. When compared with the CK, SSP, BC and CMP reduced the total REE concentrations in rice roots by 82.2%, 67.9% and 89.6%, shoots by 75.4%, 40.1% and 65.5%, grains by 23.8%, 29.0% and 29.3%, respectively. PR, SSP, BC and CMP significantly reduced the concentrations of REEs in the soil solution at three stages of rice growth. Analytic results of X-ray diffraction shows that adding PR, SSP, BC and CMP can lead to the formation of rare earth phosphate in the soil, thus reduce the activity of the REEs in the soil. Because SSP releases H+ during its dissolution, which has the risk of activating REEs in soil, CMP and BC are potential materials for remediation of REE-contaminated soil.