| Energy crops switchgrass root system developed,can form mycorrhizal symbiosis with fungi,with strong resistance and high nutrient absorption and utilization efficiency.At present,the shortage of available phosphorus in alkaline soil is serious,and phosphorus is a necessary nutrient element for crop growth and development.Therefore,in this experiment,two ecotypes of switchgrass were used as the research object,and three phosphorus levels of 0 kg · hm-2,30 kg·hm-2 and 90 kg · hm-2 were set up to explore the relationship between phosphorus absorption and utilization characteristics of switchgrass in saline-alkali soil and plant agronomic traits,physiological characteristics and rhizosphere soil microbial ecological characteristics.The effect of phosphorus application on the diversity of arbuscular mycorrhizal fungi(AMF)in switchgrass was analyzed,which provided a theoretical basis for biological improvement and phosphorus absorption and utilization of energy crops in saline-alkali soil in northwest arid areas.The main research results were as follows:1.Appropriate phosphorus application promoted the growth and development of switchgrass in saline-alkali soil and improved its physiological activity.With the increase of phosphorus application rate,the agronomic traits such as plant height,tiller number,above ground dry matter accumulation and physiological indexes such as net photosynthetic rate,water use efficiency and antioxidant enzyme activity of switchgrass showed an increasing trend.Compared with the control,the above ground dry matter accumulation,net photosynthetic rate and peroxidase activity of Alomo varieties increased by 23.42%,5.89%and 51.19%,respectively.The dry matter accumulation in the above ground part of the Pathfinder cultivar increased by 11.82%,the net photosynthetic rate increased by 4.55%,and the peroxidase activity increased by 34.76%.Compared with the highland Pathfinder variety switchgrass,the lowland variety switchgrass Alamo had a large increase in the overall growth and physiological indexes,and had strong advantages in growth,development and physiological characteristics,high biomass yield potential and stronger response to phosphorus.2.Appropriate phosphorus application increased the nutrient content of rhizosphere soil of switchgrass in saline-alkali soil,and improved the soil fertility level of rhizosphere soil of switchgrass.With the increase of phosphorus application rate,the pH value and salt content of rhizosphere soil of switchgrass showed a downward trend as a whole,and the total phosphorus,available phosphorus content,phosphatase activity and inorganic phosphorus content showed an increasing trend.Compared with no phosphorus treatment,the total phosphorus content,available phosphorus content and alkaline phosphatase activity of switchgrass rhizosphere soil of Alomo cultivar increased by 16.24%,43.57%and 35.70%,respectively.Pathfinder variety switchgrass rhizosphere soil total phosphorus content increased by 12.49%,available phosphorus content increased by 49.45%,alkaline phosphatase activity increased by 29.15%.Compared with highland Pathfinder switchgrass,lowland switchgrass Alamo soil phosphorus content increased greatly.3.Phosphorus application reduced the diversity index of arbuscular mycorrhizal fungi(AMF)a in rhizosphere soil of switchgrass at flowering stage,which may inhibit the microbial activity in rhizosphere soil of switchgrass in saline-alkali soil.Compared with no phosphorus treatment,AMF Observed index,Chaol index,ACE index and Shannon index of switchgrass rhizosphere soil of Alomo varieties decreased by 8.02%,11.54%,10.33%and 71.20%,respectively.Pathfinder cultivar switchgrass rhizosphere soil AMF Observed index decreased by 2.70%,Chaol index decreased by 2.68%,ACE index decreased by 1.36%,Shannon index decreased by 7.03%.Soil fungal richness and P diversity did not change significantly.Compared with the highland Pathfinder variety switchgrass,the diversity index of AMF a in rhizosphere soil of switchgrass Alamo in lowland variety changed greatly,which was strongly affected by environmental factors,and the activity of arbuscular mycorrhizal fungi(AMF)was relatively strong.4.Appropriate phosphorus application increased the phosphorus content and phosphorus accumulation in stems,leaves,spikes and above ground parts of switchgrass in saline-alkali soil,and promoted the phosphorus absorption and utilization efficiency of switchgrass.It was also found that phosphorus uptake efficiency of switchgrass was closely related to available phosphorus content,Shannon index,plant phosphorus content and phosphorus accumulation in rhizosphere soil.Compared with highland Pathfinder switchgrass,lowland switchgrass Alamo had higher phosphorus uptake and utilization efficiency under the same phosphorus application condition. |
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