Effects Of Straw Returning Technology Of Large Ridge Rotation Sowing Of Spring Maize On Root System And Microecology

Corn is the largest food crop in China,and corn straw treatment is an urgent environmental problem,while straw returning can not only improve the environment but also increase soil fertility,which is the core technology of conservation tillage.Suitable straw returning tillage can adjust soil water,fertilizer,gas,heat,microorganism and other environmental factors,improve soil maize root micro-zone environment,promote high and stable yield of maize.According to the characteristics of low temperature and water shortage in cold and arid regions of northwest Hebei province,the effect of straw returning with large ridge rotation on spring maize root system and microecological environment was studied.By analyzing root biomass,rhizosphere soil microbial biomass,enzyme activity,DOM characteristics and spatial and temporal distribution characteristics of environmental factors at different growth stages of maize,the effects of rotation planting with large ridge on root and microecology were revealed.It provides theoretical support for straw returning technology in cold and arid regions.The results are as follows:（1）The dry weight of spring corn roots is 196.5～286.8 g,which is 45.95%higher than that of the control.The root-shoot ratio is between 0.12 and 1.09,which is 21.11%higher than that of the control.Compared with the control,the root tip number and root length of straw returning to the field increased by 14.83%and 18.07%respectively.Root surface area increased by 39.19%;The total root absorption area of straw returning to the field is between 0.02and 0.25m²,which is 12.5%higher than that of the control.The active absorption area is between 0.01 and 0.15m²,which is significantly increased by 59.09%compared with the control.Root activity is between 1.9%and 37%,which is 32.6%higher than that of the control.On the whole,the dry weight,root tip number,root length,root surface area,root-shoot ratio,total absorption area,active absorption area and root vigor of spring maize can be significantly improved by returning straw to the field in large ridge rotation.（2）The DOC content of soil after returning straw to the field in big ridge rotation is between 14.67 and 16.55 mg·kg^-1,which is increased by12.82%compared with the control.3DEEM-PARAFAC method was used to analyze soil DOM.The results showed that the tryptophan-like protein C1 of straw returning soil was between 4.27%and 8.45%,Significantly reduced by31.68%compared with the control,the fulvic acid C2 was between 7.14%and 21.06%,Significantly increased by 47.49%compared with the control,the microbial humus C3 was between 24.48%and 31.66%,which is significantly increased by 7.21%,Humic acid C4 is between 9.54%and13.40%,which is significantly increased by 6.75%,while tyrosine protein C5is between 26.20%and 50.67%,which is significantly increased by 4.75%.On the whole,straw returning in big ridge rotation can significantly increase the proportion of fulvic acid in soil DOM and reduce the proportion of tryptophan protein in soil.（3）With the development of spring corn,the MBC content of soil with straw returning is between 481.93 and 491.72 mg·kg^-1,and the highest in the filling stage,which is 2.03%higher than that of the control.The content of MBN in soil is between 99.41 and 101.69 mg·kg^-1,which is the highest in the mature period,which is 2.29%higher than that of the control.The content of MBP in soil is between 4.32 and 7.01 mg·kg^-1,which is the highest in the mature period,which is 62.27%higher than that of the control.With the development of spring corn growth,the invertase activity in soil with straw returned to the field was between 14.73 and 18.24 mg·kg^-1,which was the highest at the grain filling stage,significantly increased by 23.83%compared with the control.Soil urease activity was between 28.79 and 47.53 mg·kg^-1,which was the highest at seedling stage,which was significantly increased by 39.43%compared with the control.On the whole,the soil microbial activity of spring corn in each growth period can be significantly improved by the rotation sowing straw in big ridge.（4）With the extension of the growth period of spring corn,the rhizosphere soil temperature of straw returning to the field showed a trend of first increasing and then decreasing,reaching the highest at jointing stage,which was significantly increased by 11.4%compared with the control;The soil moisture content fluctuates,and it is the highest at the mature stage,which is significantly increased by 12.71%compared with the control.The pH value of soil increased at first and then decreased,reaching the highest value at the mature stage,which was 5.17%lower than that of the control.On the whole,long ridge rotation sowing straw returning to the field can significantly increase the soil temperature,soil moisture content and reduce the soil pH value of spring corn in each growth period,and straw returning to the field can improve the rhizosphere soil microenvironment,thus making the corn yield high and stable.Straw returning can improve the soil micro ecological environment,promote the proportion of small molecule DOM,improve soil microbial activity,promote root growth,delay the decline of corn root at maturity,and provide a good farming environment for corn growth and yield formation.