Study On Preparation Of Soil Amendment By Chinese Herb Residue And Its Application In Rare Earth Mining Area

Jiangxi Province is a big province of traditional Chinese medicine industry,one of the“four big drug capitals”.The development of traditional Chinese medicine industry is accompanied by a large number of organic waste residue,which needs to be properly treated.A large number of contaminated soil in Jiangxi Gannan rare earth mining area also needs to be repaired.In this study,the organic waste residue of a pharmaceutical factory in Jiangxi was selected to prepare the soil conditioner for the remediation and improvement of soil aggregate structure in rare earth mining areas by composting process.On the basis of determining the optimum process parameters for the preparation of organic modifier of Chinese medicine residue,the single repair effect of organic modifier of Chinese medicine residue was optimized by compounding it with inorganic material zeolite and nano iron.At the same time,a commercial organic fertilizer modifier was purchased as a comparison sample.The application effect of traditional Chinese medicine residue modifier was discussed by indoor soil culture test and pot experiment,and its remediation mechanism for soil in rare earth mining area was discussed.This study provides a new economic and effective choice for the functional restoration of soil structure in rare earth mining areas,provides a new example and theoretical basis for the preparation and application effect of organic-inorganic composite soil conditioners,and also finds an effective resource utilization path for organic waste residue.The main conclusions are as follows:（1）Determination of Optimum Process Parameters for Composting of Traditional Chinese Medicine Residue by Single Factor Test:The C/N ratio,water content and microbial agent addition were selected as the influencing factors of composting process.The temperature,solid C/N ratio,seed germination index（GI）,p H value and E₄/E₆ were used as the indexes to determine the maturity of composting.The optimal levels of each factor were determined as 25:1,65%and 0.5%,respectively.（2）Compound optimization test of TCM slag modifier:a.The content of soil organic matter in each treatment increased by 3.31～4.37times compared with the control group,and the effect of compound amendments with0.5%zeolite added Chinese medicine residue was the best.The content of soil organic matter in treatment 9 was 29.38 g/kg at the end of culture,which was close to the nutrient classification standard of the second national soil census 30 g/kg.The improvement effect of zeolite 2%and nano-iron 0.5%was almost the same as that of treatment 9.b.The addition of zeolite and nano-iron was proportional to the total nitrogen content in soil,and the No.1 soil with the largest addition of zeolite and nano-iron had the highest total nitrogen content.c.Compared with the control group,the total phosphorus content in the soil treated with different proportions of modifiers increased by 1.86～2.75 times.When the amount of zeolite and nano-iron was 1%,the soil phosphorus content was the highest.e.Compared with the control group,the total potassium content in the soil treated with each modifier increased by 0.31～0.40 times.f.The average soil mass diameter MWD and geometric mean diameter GMD were the largest and the stability of soil aggregates was the strongest under the ratio of 10%organic modifier of Chinese medicine residue+2%zeolite+0.5%nano iron（accounting for soil mass ratio）.（3）Indoor soil culture experiment was conducted to explore the remediation effects of organic modifiers of Chinese medicinal residue,compound modifiers of Chinese medicinal residue and commercial organic fertilizer modifiers:a.The soil nutrient content of each treatment was higher than the control value,and the improvement effect of organic modifier of Chinese medicinal residue on soil solidarity stability and soil nutrients would increase with the increase of the addition amount,but the soil potassium content was almost unaffected.b.The repair effect of compound Chinese medicine residue modifier is better than single Chinese medicine residue organic modifier and commercial organic fertilizer modifier.In addition,the compound amendments of Chinese medicine residue had little effect on soil phosphorus content.c.When the addition amount of commercial organic fertilizer conditioner was 20%（accounting for soil mass ratio）,the MWD was the largest and the stability of soil aggregates was the strongest.（4）To further explore the application effect of different kinds of amendments by pot experiment:a.Soil organic matter content increased significantly after all amendments.The soil nutrient content of the blank control group was generally higher than that of the control group.b.The improvement effect of compound modifiers of Chinese medicinal residue was better than that of organic modifiers of Chinese medicinal residue.The increase in the addition amount of organic modifiers of Chinese medicinal residue and commercial organic fertilizer modifiers could promote the improvement effect,and the effect of organic modifiers of Chinese medicinal residue was better with the increase of cultivation time.c.The increase of soil total nitrogen content by the compound modifier of Chinese medicinal residue made of organic materials and inorganic materials was better than that by the single organic modifier of Chinese medicinal residue and commercial organic fertilizer modifier.d.The maximum MWD and GMD and the maximum stability of soil aggregates were obtained when the organic modifier content was 10%.