| The ecological environment in the contiguous areas of Shanxi,Shaanxi and Inner Mongolia in northwestern China is seriously damaged due to the exploitation of minerals,and the restoration of ecological vegetation in the area is imminent.Aeolian sandy soil is one of the main soil types with little or no structure in this area,it is highly permeable and retains little or no water.Pisha sandstone is widely distributed in this area as an underlying stratum,it is a kind of loosely bonded sandstone with strong water absorption capacity.The aeolian sandy soil and Pisha sandstone are complementary in nature,Pisha sandstone can be used to amend the aeolian sandy soil to improve the water and fertilizer retention capacity of soil.Water and fertilizer are key factors for plant growth,but their effectiveness on plants are affected by soil properties.In order to investigate the response of plants in the amended soil to the application of water and phosphate fertilizers,a pot experiment was carried out to grow alfalfa?Medicago sativa?in aeolian sandy soil and Pisha sandstone-amended aeolian sandy soil.The objective of this study was to investigate the interactive effects of water and phosphorus?P?supply,and rhizobia inoculation on the growth,nutrient uptake and ecophysiology characteristics of alfalfa,and provide a theoretical basis and reference for the vegetation restoration in the contiguous areas of Shanxi,Shaanxi and Inner Mongolia.The results are as follows:?1?In both non-inoculated or inoculated treatments,dry mass of alfalfa was the greatest in Pisha sandstone-amended aeolian sandy soil with high P(20 mg·kg-1)and sufficient water supply?70%field capacity?,in which shoot dry mass of the first cut had a maximum increase of 380%,shoot dry mass of the second cut had a maximum increase of 587%,root dry mass had a maximum increase of 138%,when compared with alfalfa grow in the aeolian sandy soil without P apply under drought stress?35%field capacity?.Plant growth,photochemical efficiency?Fv/Fm?,the effective quantum yield?Y?II??,nodule numbers,aboveground plant P and N concentrations,aboveground plant P and N acumulation in both soils were increased when P was supplied The application of P can weaken the negative effect of drought stress,and improve plants'drought resistance.?2?Drought stress inhibited plant growth in the two soils,alfalfa biomass,leaf and stem P concentrations,aboveground plant P and N accumulation in the sufficient water supply treatments were significant higher than those in drought stress treatments,indicating that increasing water supply can promote plant growth and improve the effectiveness of phosphorus fertilizer on plants.?3?Rhizobia inoculation had no significant effect on plant growth and nutrient uptake,but increased the number of nodules,therefore could improve nitrogen fixation efficiency and reduce the dependence of plant growth on nitrogen fertilizer.?4?The effects of P and water application on plants varied between soil types.Pisha sandstone-amended aeolian sandy soil had a higher productivity,plants grown in Pisha sandstone-amended aeolian sandy soil had higher dry mass,leaf and stem P concentrations,aboveground plant P and N acumulation than those grown in aeolian sandy soil under the same water and P conditions,indicating that the application of water and P is more effective for plants and the resource utilization efficiency is higher in the amended soil.?5?Root acid phosphatase activity decreased when P was supplied,and positively correlated with P-utilisation efficiency,indicating that plants under low P stress would regulate the utilization of organic P by enhancing acid phosphatase activity.Rhizosphere carboxylates mainly included tartarate,oxalate,malate,malonate and citrate,and the amounts were affected by P application level.More carboxylates were released into the rhizosphere when no P was supplied,and such increase in rhizosphere carboxylates is a strategy for alfalfa to improve P mobilization in the studied soils when soil P supply is low.Rhizosphere pH was much lower than bulk soil pH,and such a decrease in pH would enhance the availability of rhizosphere P.Based on the above results,Pisha sandstone-amended aeolian sandy soil is conducive to plant growth and effective use of resources,it is promising to be used for the vegetation restoration in the contiguous areas of Shanxi,Shaanxi and Inner Mongolia in northwestern China.Appropriate application of phosphate fertilizers and water can improve plant growth,and accelerate the process of vegetation restoration. |
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