| Saline-alkali soil is an important part of available land in China with characteristics of wide distribution and various types.The improvement and utilization of saline-alkali soil have become one of the important approaches to the sustainable development of agriculture in China.Phytoremediation could produce ecological and economic benefits simultaneously and then is considered as a promising way to improve the saline-alkali soil.Miscanthus is a plant with high yield potential and strong tolerance to saline-alkali soil and is considered as a candidate that can be used to improve the saline-alkali soil.However,the exact improvement potential is still unclear.This study is then designed to evaluate the soil improvement potential by planting miscanthus on saline-alkaline soil,including improving the soil physical and chemical properties and soil microbe community.Additionally,this study also explores and tests the utilization potential of miscanthus biomass as biofertilizer,which can increase the economic feasibility of saline-alkaline soil phytoremediation by miscanthus.The main conclusions of this study are as follows:(1)After growing miscanthus on saline-alkali soil,the physical and chemical properties of soil was significantly improved,which can be proved by that: the soil p H dropped from 8.86 to 8.44,the electrical conductivity dropped from 281 livs /cm to 203 livs /cm(indicating reducing the total amount of salt in the soil significantly),organic matter content changed from 14.63 g/kg to 34.89 g/kg,total nitrogen content changed from 0.50 g/kg to 0.67 g/kg,total phosphorus content changed from 0.69 g/kg to 0.86 g/kg.(2)The soil microbe community structure and composition were also improved by miscanthus planting compared with the soil without miscanths cultivation.The soil after G1 cultivation shows the highest bacterial community diversity,while soil after G2 cultivation had the highest fungal and bacterial community richness.The relative abundance of the fungus genera and the bacteriaceae was also significantly different between soil after cultivating different miscanthus genotypes.Podospora in G1,and Podospora,Schizothecium,Sphingomonadaceae in G2,and Micrococcaceae in G3 were significantly higher than that in blank control CK.The RDA analysis showed that the main environmental factors affecting the composition of soil fungal community were total phosphorus,while the main environmental factors affecting the composition of soil bacterial community were p H,total potassium,organic matter and total organic carbon.Further interaction analysis with environmental factors revealed that the Podospora,Schizothecium,and Sphingomonadaceae were all positively correlated with organic matter,total organic carbon,and carbon-nitrogen ratio.The relative abundance of micrococcaceae was positively correlated with total potassium and negatively correlated with p H.(3)In the experiments of screening optimistic miscanthus fermentation condition,T1(aerobic fermentation + fermentation with pig manure as N source)treatment experienced the highest number of days of high temperature(29 d).Its fermented biomass p H,carbon and nitrogen ratio,and the seed germination index reached the standards of ripening the earliest,and the comprehensive time of ripening process was the shortest.The total porosity,pore ratio,humus quality and total nutrient content(nitrogen + phosphorus pentoxide +potassium oxide)of T1 products were significantly higher than those of the other treatments,and its density was the most suitable for plant cultivation as substrate.Its organic matter content met the standard,and the product quality was the best among the four treatments.In summary,the most suitable method for the fermentation of miscanthus biomass is T1.(4)There was no significant difference between the leaf length,leaf spread amplitude between the commonly used moss substrate(as CK)and our produced cultivation substrate I(CS-I,Miscanthus rotten product: Miscanthus biochar: Humic acid=14:3:3),while its leaf width and leaf area lower than that of CK(not significantly).The orchids planted in CS-J(mushroom residue derived from Miscanthus: Miscanthus biochar=3:1),CS-K(mushroom residue derived from Miscanthus: Miscanthus biochar: Humic acid: Ceramsite=6:4:6:3)and CS-M(mushroom residue derived from Miscanthus: Miscanthus biochar: Humic acid:Ceramsite=4:1:3:3)performed better or even significantly higher than that of CK in leaf length,leaf width,leaf area and leaf spread,and SPAD.The above results indicate that our produced substrate CS-I,CS-J,CS-K,CS-M can be used to grow orchid instead of the commonly used water moss.(5)The clematis planted in cultivation substrate E(CS-E,Miscanthus rotten product:Miscanthus biochar: Humic acid=11: 2: 6)is the best among the five treatments in terms of plant height,stem diameter,leaf length,and leaf area.There was no significant difference between cultivation substrate A(CS-A,Miscanthus rotten product: Miscanthus biochar=8:1)and the commonly used soil substrate(as CK)in the plant height?stem diameter?leaf length and leaf area,cultivation substrate H(CS-H,Miscanthus rotten product: Miscanthus biochar:)and cultivation substrate I(CS-I,Miscanthus rotten product: Miscanthus biochar:Humic acid=14:3:3)were not significantly different from CK in plant height,leaf length and leaf area,and there was no significant difference in SPAD between the five treatments.Therefore,it is considered that the cultivation CS-A,CS-E,CS-H,and CS-I can replace the cultivated soil as the cultivation substrate of Anoectochilus roxburghii. |
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