| The surface subsidence resulted from coal mining has destroyed vegetation growth and the balance of groundwater system,which in consequence leads to soil nutrient deficiency and water shortage,and thus exacerbates the survival circumstance of plants and hinders the sustainablility of farmland in mining regions.Plastic film mulching,as an effective technology in dry farming,has obvious effect on increasing soil temperature and water retention,and thus in favor of plant growth and higher yield of crops.Arbuscular mycorrhizal fungi(AMF)are the symbiont that formated between the fungal hyphae in soil and plant roots,which can play an important eco logical function in plant-AMF-soil ecosystem.Therefore,the combination of plastic film mulching and AMF inoculation has important practical significance for crop water saving and soil improvement in the arid regions of Northwest C hina.In this study,using two years of greenhouse experiment and field trials in 2014 and 2015,and taking the perspective of the interaction between AMF and phosphatase-solubling bacteria(PSB)or their interactions with film mulching patterns and different levels of weathered coal addition,this study carried out a greenhouse experiment of mycorrhizal effect on maize growth under film mulching patterns,a field trial of film mulching and microbial inoculation on maize growth and water use efficiency,and the study of mixed substrate on growth promoting effect of maize and soil enzyme activity in the condition of water stress,the research on root morphology of maize and soil properties associated with different level of weathered coal addition in mining regions.Through the four experiments above,this study tries to tackle the issue of soil poor nutrient and drought in crop ecosystem of coal mining subsidence regions in China.The main results were as follows:1.The sand culture in the greenhouse was carried out to study the effect of two film mulching patterns(non-mulching and film mulching)and four microbial inoculation levels(AMF inoculation,PSB inoculation,co-inoculation of AMF+PSB,CK)on maize growth,shoot nutrient accumulation and AMF characterstics under two water regimes(normal water and water stress).Results showed that drought stress increased mycorrhizal colonization of maize root compared with normal water condition.AMF inoculation or co-inoculation of AMF+PSB significantly improved soil external hyphal length,EE-GRSP and SOC content,but significantly reduced soil total nitrogen,Olsen P and available K content(except for the AMF inoculation treatments under normal water condition)compared with PSB inoculation or CK treatment under two water regimes(P<0.05),thus promoted the shoot N,P and K accumulation of maize.Under water stress,the combination of film mulching and AMF inoculation significantly improved plant growth,of which the water use efficiency was ma rkedly increased than that of CK treatment by 47.2%-52.6%(P<0.05),while under normal water condition,the combination of film mulching and AMF+PSB inoculation showed the better promotion effect than the combination of film mulching and AMF inoculation,of which the water use efficiency was markedly increased than that of CK treatment by32.3%-36.0%(P<0.05).2.The field trial in 2014 was conducted to investigate the effecet of three film mulching patterns(non-mulching,half mulching and full mulching)and four level of microbial inoculation(AMF inoculation,PSB inoculation,co-inoculation of AMF+PSB,CK)on maize growth and water use efficiency under irrigation and rainfed in coal mining subsidence regio n.Results showed that the plant height,biomass,yield and water use efficiency were increased with the trend of non-mulching to half-mulching to full-mulching pattern under irrigation and rainfed.Under the influence of indigenous AM fungi and soil environment,the root mycorrhizal colonization of AM-inoculated maize was relatively low(17.8%-32.2%).Averaged across three film mulching patterns,AMF inoculation or co-inoculation of AMF+PSB significantly improved root mycorrhizal colonization,soil externa l hyphal length and GRSP content,and promoted the transport of soil nutrients compared with the CK treatment(P<0.05).The combination of full mulching and AMF inoculation significantly improved maize growth compared with the other combinations,of which the water use efficiency and yield were significantly increased than that of CK treatment by 20.0%-24.9%and19.4%-32.7%,respectively(P<0.05).3.A pot culture simulated the interaction of soil substrates(sandy substrate and mixed substrate),film mulching patterns(non-mulching and film mulching)and microbial inoculation(AMF inoculation and CK)on plant growth,water use efficiency and soil enzyme activity under water stress condition.Resluts showed that there were no significant differences on root mycorrhizal colonization and soil external hyphal length between sandy substrate and mixed substrate.The AMF inoculation of mixed substrate significantly improved soil T-GRSP and EE-GRSP content compared with that of sandy substrate(P<0.05).Compared with the sandy substrate,the mixed substrate associated with the combination of AMF inoculation and film mulching significantly increased the water consumption during growth period,but reduced the transpiration coefficient and the mycorrhizal dependence of nutrient accumulation of maize aboveground,and thus improved plant height and biomass(P<0.05),indicating that mixed substrate is in favor of improving plant water and nutrient use efficiency.In addition,the mixed substrated associated with AMF inoculation or CK treatments significantly increased soil invertase activity under non-mulching,soil catalase and alkaline phosphatase activities under film mulching compared with the sandy substrate with the corresponding treatments(P<0.05).4.The field trial in 2015 was conducted to study the effect of film mulching and AMF inoculation on maize growth,root morphology and soil properties under three level of weathered coal addition(0,1.5 and 3 kg/m~2).Results showed that the 1.5 and 3kg/m~2 weathered coal showed no significant effect on root mycorrhizal colonization,plant height,biomass and leaf SPAD value,and soil external hyphal length,but decreased water use efficiency and yield of maize under full mulching when compared with non-weathered coal addition treatments.The 1.5 kg/m~2 weathered coal treatments increased root tip number,length and surface area of maize,but significantly reduced root volume of maize compared with non-weathered coal addition treatments(P<0.05).The 1.5 and 3 kg/m~2 weathered coal decreased rhizosphere soil invertase and urease activities,while the 1.5 kg/m~2 weathered coal increased soil catalase activity,the average of which was increased by 3.7%-5.0%compared with the non-weathered coal addition treatments.Under the same level of weathered coal addition,the combination of AMF inoculation and full mulching showed the better promotion effect on maize growth,water use efficiency and yield,which was in line with the results of the field trial in 2014.5.The PCA results of two greenhouse experiments showed that the cumulative contribution of the first two principal components reached 90.45%.The first principal component was related to factors of mycorrhizal colonization,plant biomass,shoot N and P accumulation,and soil external hyphal length and SOC,and the second principal component was related to the shoot K accumulation factor,both of which showed positive on plant growth under water stress condition.The comprehensive principal component value of four combination habitats ranked as follow:AMF+film mulching(0.989)>AMF inocualtion(0.655)>film mulching(-0.694)>the control(-0.951),indicating that the combined AMF and film mulching can promote plant growth than AMF inoculation or film mulching under water stress.In conclusion,the combination of full film mulching and AMF showed a significant positive effect on maize growth,water use efficiency and yield,and improved soil properties,especially under drought condition.The research provides a novel way to excavate the potential of crop gowth and land productivity in the circumstance of soil poor nutriency and water stress in arid or semiarid regions of Northwest China. |
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