Effects Of Fertilization Levels On Growth And Rhizosphere Soil Properties Of Super Hybrid Rice

In this study,super hybrid rice“Xianliangyou 900”was used as test material to determine the growth status of rice,rhizosphere soil enzyme（urease,invertase and catalase）activity,rhizospheric soil physicochemical properties（pH,organic matter,available nitrogen,available phosphorus and available potassium）and rhizosphere soil bacterial community structure under different fertilization levels（pure nitrogen 0,150,225,150,375,450 kg/hm²,N:P₂O₅:K₂O=1:0.5:1）.The optimal fertilization level was determined by comprehensive analysis,which provided scientific basis for high yield and high efficiency of super hybrid rice.Main results for this study are as follows:1.The effects of different fertilization levels on the growth of super hybrid rice.With the increase of fertilization level,tillers number,above-ground dry matter weight and LAI at the tillering stage and the full heading stage,root dry weight at full heading stage,SPAD value at mature stage all increased gradually,but the difference in high fertilization treatment（375,450kg/hm²）was not significant.During the mature period,the aboveground matter weight,plant height,theoretical yield,and actual yield all increased first and then decreased with the increase of fertilizer application.When pure nitrogen was 300 kg/hm²,the above-ground dry matter weight,theoretical yield and actual yield were the highest,which were 19036 kg/hm²,11863 kg/hm² and 9851 kg/hm²,respectively.The increase of fertilizer application can significantly increase the number of effective panicles of rice,but it will reduce the number of grains per panicle and the seed setting rate;fertilization can significantly increase the 1000-grain weight of rice,but the difference between the fertilization treatments did not reach a significant level.2.The effects of different fertilization levels on rhizosphere soil enzyme activity of super hybrid rice.With the increase of fertilization level,the urease activity in rice rhizosphere soil at the tillering and full heading stages gradually increased,and there was significant difference at the full heading stage.The urease activity in the mature stage first increased and then decreased.With the increase of fertilizer application,the activity of invertase in rice rhizosphere soil was significantly increased,but there was no significant difference in the amount of high-fertilizer treatment（375,450 kg/hm²）.Fertilization could significantly reduce the activity of catalase in the rhizosphere soil of rice at full heading and maturing stages,and there was no significant difference among the fertilization treatments.3.The effects of different fertilization levels on rhizosphere soil physicochemical properties of super hybrid rice.With the increase of fertilizer application,the pH of rice rhizosphere soil decreased gradually,the available phosphorus and available potassium increased gradually,but the content of organic matter did not change significantly.In the tillering and heading stages,the content of available nitrogen in the rhizosphere soil increased first and then decreased with the increase of the amount of fertilizer,and it gradually decreased during the ripening period.4.The effects of different fertilization levels on rhizospheric soil bacterial community structure of super hybrid rice.The fertilization reduced the diversity and species richness of bacterial communities in the rhizosphere soil at full heading and maturing stages,but there was a certain difference between fertilization treatments,but it was not significant.During the same growth period,fertilization did not change the dominant bacteria in rice rhizosphere soil,but changed their relative abundance.There are certain differences in the main bacterial species at full heading stage and mature stage.There are also some differences in the main bacteria at full heading stage and mature stage.The Firmicutes and Latescibacteria replaced Cyanobacteria and Chlorobi as the main bacteria in the mature stage.The main environmental factors affecting the bacterial community structure at heading stage are pH,available nitrogen,available phosphorus and organic matter,and the maturation period is pH,organic matter,available phosphorus and available potassium.Based on the above results,it can be seen that when the pure nitrogen content is 300kg/hm²,the enzyme activity in the rhizosphere of the super hybrid rice is higher,the available nutrients are adequate,the pH is moderate,the bacterial community structure is similar to other fertilization treatments,the growth indicators are balanced,and the yield is the largest,which is a reasonable fertilization level under the experimental conditions.