Study On Root Morphology,Physiology And Complementary Advantages Of Maize With Different Nitrogen Efficiency In Obtaining Soil Nitrogen

Corn plays a very important role in the production of food crops in China,and is widely planted in northern China.Nitrogen in soil environment is a key factor affecting crop growth and development.It is one of the essential nutrients in the process of plant growth and development.Different types and forms of nitrogen can improve crop yield and quality in different degrees.In this paper,two nitrogen efficient maize varieties,Zhengdan 958（Zea mays L.cv.ZD958）（Low nitrogen and high efficiency）and Xianyu 335（Z.mays L.cv.XY335）（High nitrogen and high efficiency type）,were used to study the root growth status,nitrogen and phosphorus absorption and distribution mechanism,amino acid content and composition,nitrogen and phosphorus accumulation and accumulation of two maize varieties.The structure and function of rhizosphere bacterial microbial community and the response of different planting patterns（single and mixed）to three nitrogen forms（NO₃^-,NH₄NO₃ and NH₄⁺）supply in different growth periods preliminarily revealed the differences of root morphology and physiological characteristics,the changes of rhizosphere bacterial microbial community structure and function,and the effects of planting patterns on the growth and development of Maize under different nitrogen forms.It provides a reference for the application and utilization of nitrogen fertilizer in maize research and Cultivation in the future,and has a very important significance for the future maize root/rhizosphere nutrition research and practical production and life.The main results are as follows:1.Total ammonium nitrogen and ammonium nitrate mixed nitrogen could inhibit the root growth of XY335 seedling stage,and the root growth of ZD958 seedling stage was inhibited by excessive ammonium nitrogen.NO₃^-could increase the total root length（15.2%-31.95%）and average root diameter（14.05%-20.98%）of maize root to a certain extent,but the root volume and root surface area decreased by 13.50%-47.30%and 13.78%-19.30%respectively.The total amino acid content of zd958 increased with the introduction of NH₄⁺.The total amount of amino acids in XY335 seedlings supplied by single ammonium nitrogen was significantly higher than 53.74%and 178.03%of nitrate nitrogen and ammonium nitrate mixed nitrogen.The results showed that ammonium nitrogen was beneficial to the increase of amino acid content in two maize varieties.Single supply of nitrate and ammonium was beneficial to the accumulation of total amino acids in XY335 seedlings.2.The effect of nitrogen forms on the similarity of bacterial communities in maize rhizosphere was relatively high,and the bacterial communities in the tested sample groups were clustered according to nitrogen forms.The bacterial richness and diversity in rhizosphere of the two maize varieties increased gradually with the increase of NO₃^-,and there was no significant difference in the bacterial community composition of rhizosphere supplied by three nitrogen forms at the gate level.At phylum level,Actinobacteria,Proteobacteria and Acidobacteria are the dominant phylum.The dominant species at genus level were bacillus,Pseudomonas and unidentified Acidobacteria.The spatial heterogeneity of rhizosphere bacteria metabolic function of ZD958 and XY335 supplied by three nitrogen forms at seedling stage was small,and the response to nitrogen forms and varieties was not obvious.3.In the follow-up stage of maize growth,under the supply of nitrate nitrogen and nitrate ammonium mixed nitrogen,mixed cropping was beneficial to improve the dry weight,nitrogen and phosphorus accumulation of ZD958 seedling stage.Under the supply of nitrate and ammonium nitrogen,the dry weight and nitrogen and phosphorus accumulation of XY335 seedlings of single species were slightly better than those of mixed species.During the 35 days growth period,the dry weight,nitrogen and phosphorus accumulation of single and mixed maize seedlings supplied by three nitrogen forms showed an increasing trend.The effects of planting methods on the contents of nitrogen and phosphorus and SPAD value of chlorophyll in maize seedling stage were not significant.With the extension of maize seedling growth time,the contents of nitrogen and phosphorus and SPAD value of chlorophyll in leaves of single and mixed maize seedlings decreased.The soil p H of ZD958 was greatly affected by nitrogen forms and planting patterns in different growth periods.The soil available nitrogen of the two maize varieties was greatly affected by nitrogen forms at the early growth stage.With the extension of growth period,the effects of planting methods and nitrogen forms on soil available nitrogen and available phosphorus were not significant.The content of soil available phosphorus in the environment of maize growth and development at seedling stage decreased gradually with the extension of growth period.The root dry weight,total root length,root surface area and root volume of two maize varieties increased with the extension of growth period.The average root diameter first decreased and then increased,and the root indexes of the two maize varieties were more affected by nitrogen forms under the mixed cropping mode.