Effects Of Microplastics And Phosphorus Addition On Maize Growth And Soil Properties

Plastic products are widely used in industry,agriculture and People’s Daily life.While it brings great convenience to people,it also causes serious ecological problems.Microplastics(MPs)refer to plastic fragments or particles with particle size less than 5mm.Due to their characteristics of small particle size and weak degradation ability,they are easy to enrich in sediments,soil and other media,and can continue to exist in the environment for hundreds or even thousands of years,so they are regarded as a potential persistent organic pollutant.At present,the research on the impact of microplastics on terrestrial ecosystems,especially agricultural ecosystems,has just started.Microplastics entering the soil,due to their strong adsorption,change the cycle of plant nutrient elements in the soil,thereby affecting crop growth.However,the interactions between microplastics,soil nutrients and crops and their mechanisms are still unknown.In this study,maize was taken as the research object,and the potted experiment was adopted to study the effects of microplastics and phosphorus addition on the growth of the maize and soil properties.The main results were as follows:(1)C1 microplastics has no significant effect on various indexes of maize growth.For C2 and C3 concentration treatments,maize plant height and biomass are significantly reduced,and corn root length,root surface area,and root volume are significantly increased.Phosphorus addition can promote maize plant height and root,but has no significant effect on maize biomass.In addition,microplastics has varying degrees of influence on the nutrient content of various organs of corn.leaves are more susceptible to microplastics than roots and stems.Meanwhile,phosphorus addition resulted in a significant increase in the total nitrogen content of the corn stem,and the total phosphorus content of each organ increased significantly with the increase of the phosphorus fertilizer concentration.The interaction of the microplastics and phosphorus has no significant effect on corn plant height,biomass,and root morphology.(2)Microplastics significantly increased the determination results of soil organic matter,and significantly reduced total soil nitrogen,dissolve nitrogen,and soil ammonium nitrogen.The C2 and C3 microplastics significantly increase the soil available phosphorus,while the dissolve phosphorus significantly decreased.Phosphorus addition significantly increased the content of soil organic carbon,total phosphorus,available phosphorus and dissolve nutrients,and significantly reduced the content of soil nitrate nitrogen.The interaction of microplastics and phosphorus has a significant impact on soil dissolve phosphorus and available phosphorus.Specifically,in the P1 treatment,the content of dissolve phosphorus and available phosphorus decreased significantly with the increase of the microplastic concentration.However,the opposite trend was shown in the P2 treatments.(3)Microplastics inhibited soil microbial biomass C and P to a certain extent,but promoted soil microbial biomass N,BG enzyme and LAP enzyme,and intensified soil C limitation.C1 microplastics had no significant effect on soil microbial biomass,while C2 and C3 treatments significantly reduced soil microbial biomass carbon,and significantly increased soil microbial biomass nitrogen.In addition,phosphorus addition reduced the microbial biomass carbon,and promoted the microbial biomass nitrogen,phosphorus,AP enzyme,BG enzyme and LAP enzyme,all of which reached the maximum value under P1 treatment.The interaction between the microplastics and phosphorus had significant effects on soil microbial biomass,AP enzyme and LAP enzyme activities.In C1 microplastics treatments,the result of microbial biomass carbon was P1C1<P2C1,but in C2 microplastics treatments,the result was P1C2>P2C2.In addition,in the P1 phosphorus treatments,the AP enzyme activity increased with the increase of the microplastic concentration;in the P2 phosphorus treatment,the AP enzyme activity decreased significantly with the increase of the microplastic concentration.