Effect Of Exogenous Substances To Plant Growth On Clastic Coal Gangue

The coal gangue dump is so hard to be re-habited that plants directly planted on it are difficult to survive, and is problematic to conserve and manage for those survived. Former researchers have taken great efforts in studying matrix improvement, plant species selection and vegetation succession on coal gangue wasteland and have come to great achievements in these fields. However, some theoretical and technical problems are far from being resolved, and the new methods and technology concerning ecological restoration need to be summarized and improved in a theoretical pattern. Effects of exogenous substances on matrix improvement and plant growth were explored in this work. Matrix in individual treatment was prepared through mixing gangue and soil at different proportion and the matrix were improved via adding corn stalks. Specifically, individual matrix was respectively treated through adding super absorbent polymer(SAP), seed dressing with rare earth nitrate, inoculating rhizobium and inoculating arbuscular mycorrhizal fungi (AMF). Then, growth conditions, photosynthetic physiology and nutrition elements of Trifolium repens L, Festuca arundinacea L. and Amorpha fruticosa L. on the improved gangue matrix, and their effects on matrix improvement were studied. What’s more, function and amount applied of exogenous substances including rare earth nitrate, super absorbent polymer(SAP), rhizobium and arbuscular mycorrhizal fungi(AMF) in vegetation restoration of coal gangue wastelands were explored and the optimal matrix preparation pattern and matrix improvement plan were selected from those are suitable for plant survival on coal gangue dump for finding out new ratio or new plan for matrix improvement and vegetation restoration of coal gangue wasteland and further enrich the vegetation restoration mode on these wasteland.Results showed that lanthanum nitrate spraying could improve average daily growth rate of Festuca arundinacea L. on improved gangue matrix and accelerate its height growth speed. Matrix improvement and lanthanum nitrate spraying help raise water use efficiency(WUE) of Festuca arundinacea L. on coal gangue, reduce the stress upon plant from high temperature and drought; though spraying lanthanum nitrate at a high concentration might inhibit the net photosynthetic rate, suitable mixing of super absorbent polymer(SAP) and lanthanum nitrate could dissolve inhibition of net photosynthetic rate from it. The optimal treatment pattern in this study was A3B2C2D2:weight ratio of soil/gangue500g:500g, adding2g/kg SAP and30g/kg crushed corn stalks into the matrix, and foliar spraying with lanthanum nitrate solution at200mg/kg3times after emergence. Effect of adding super absorbent polymer(SAP) and seed dressing with lanthanum nitrate on the growth of Trifolium repens L. and coal gangue matrix improvement was studied in this paper. The results showed that adding super absorbent polymer into coal gangue matrix could optimize matrix structure and hydrothermal conditions to a certain extent, and improve water use efficiency(WUE) of Trifolium repens L., which promoted its height growth. Adding super absorbent polymer(SAP) and seed dressing with lanthanum nitrate solution at optimum concentration could improve net photosynthetic rate, regulate the transpiration rate of Trifolium repens L., avoid foliar burns from high temperature, effectively alleviate the heat stress, which were beneficial to promoting the of adaptability of Trifolium repens L. to high temperature of coal gangue matrix. The optimal treatment in this study was A3B3C2D2:the weight ratio of gangue/soil500g:500g, adding2g/kg super absorbent polymer(SAP) and15g/kg crushed corn stalks in matrix, and seed dressing with lanthanum nitrate solution at200mg/kg before planting.Effect of rhizobium inoculation on single sown Trifolium repens L.on improved gangue matrix was also studied in this paper. Results showed that rhizobium inoculation helped promote growth and tillering of Trifolium repens L. and increase the biomass; height of Trifolium repens L. inoculated with rhizobium increased by13.78%than that of the CK; Rhizobium inoculation both advanced the nodulation rate and nitrogenase activity of Trifolium repens L. and promoted decomposition of P and K in the matrix, which helped improve the nutritional status of the coal gangue matrix. The optimal combination program was A3B2C3D2:weight ratio of coal gangue matrix and soil500g:500g, inoculating with rhizobium bacteria liquid at the concentration of1.0×109bacteria/ml, adding1g/kg super absorbent polymer(SAP) and15g/kg crush corn stalks into coal gangue matrix.The optimal matrix program for mixing sown Trifolium repens L. and Festuca arundinacea L. was A3B1C3D2:weight ratio of coal gangue matrix and soil500g:500g, inoculating with rhizobium bacteria liquid at the concentration of1.0×109bacteria/ml, adding15g/kg crush corn stalks and Og/kg super absorbent polymer(SAP) into coal gangue matrix. The biomass of mixed sowing Trifolium repens L. and Festuca arundinacea L. increased by30.19%and40.67%after rhizobium inoculation. This was because rhizobium inoculation could increase nodulation rate of Trifolium repens L. and nitrogenase activity of coal gangue matrix, which was helpful for providing itself and the accompanying gramineous plants with more nitrogen nutrition; and the competition between gramineous plants and leguminous plants stimulated the nitrogen fixation, so as to promote plant growth. When mixed sowing, curve of daily water use efficiency (WUE) of Trifolium repens L. and Festuca arundinacea L. showed a zero-sum trend, when rational water use(WUE) of the two plants can be achieved.Arbuscular mycorrhizal fungi (AMF) also plays a significant role in the vegetation restoration of coal gangue matrix. The study found that inoculation of arbuscular mycorrhizal fungi(AMF) could enhance photosynthetic rate and water use efficiency (WUE) of Amorpha fruticosa L. on coal gangue matrix. Symbionts formed from root of Amorpha fruticosa L. and arbuscular mycorrhizal fungi(AMF) improved the nitrogenase activity of rhizosphere soil, promoted the growth of Amorpha fruticosa L. on coal gangue matrix and increased the biomass. The optimal matrix program for Amorpha fruticosa L.to grow on non-spontaneous gangue was G1ZJ2C2:weight ratio of coal gangue matrix and soil500g:500g, inoculating with Glomus intraradices. The optimal matrix program for Amorpha fruticosa L.to grow on spontaneous gangue was G2ZJ2C3:weight ratio of coal gangue matrix and soil500g:500g, inoculating with Glomus mosseae.In conclusions, the exogenous substances including rare earth nitrate, super absorbent polymer(SAP), rhizobium and arbuscular mycorrhizal fungi(AMF) have a broad application prospect in the vegetation restoration of gangue wasteland as they promote plant growth at different degrees.