| In order to select the organic materials which can increase the conversion rate of soil organic matter(ESOM),improve the composition of humus and the structural characteristics of humic acid（HA）,and increase the yield of corn,the application of corn straw（CS）,humified corn straw（HCS）and biochar from corn straw（Bc）under the condition of equal carbon content.In this study,three groups of tests were designed according to the total amount of carbon applied to the field.Test A is a small-scale pot test,which the amount of carbon applied is 2.78g kg-1.Test B is a large-scale pot test,which the amount of carbon applied is 1.84g kg-1.Test C is a micro-area test,which the amount of carbon applied is 2.72g kg-1.There are 4 treatments in each group of tests.They are:（1）do not add any material（CK）;（2）only add corn straw（CS）;（3）only add humified corn straw（HCS）;（4）only add biochar from corn straw（Bc）.Materials will not be added after the first year（2021）of application for two years.The composition of ESOM,humus and the structural characteristics of HA（element composition,infrared spectrum,thermal stability and fluorescence spectrum）were studied in three groups of experiments.The results show that:Equal amount of carbon applied to the material within two years.The increasing effects of CS,HCS and Bc on the conversion rate of soil organic matter were as follows:HCS>Bc>CS.Among them,the effect of HCS is the best and the most stable.The SOM increased 12.14%and the ESOMincreased 66.53%after two years.Both of them are much higher than CS and Bc.In addition,HCS could significantly increase soil water soluble matter carbon content（WSS-C）,soil humic acid carbon content（HA-C）and soil humin carbon content（HM-C）,and improve soil humization degree（PQ）12.59%as a whole.It shows that HCS is more beneficial to promote the process of soil humization.Comparative analysis of the structural characteristics of soil HA in three groups of tests.The results show that HCS treatment is more beneficial to improve the degree of oxidation and the proportion of aromatic substances of HA.Compared with CK,the O/C of HCS increased by5.99%,the H/C has been reduced 1.41%,Bc take second place and its O/C increased by 4.37%,the H/C has been reduced 1.23%.Although CS performed well in improving the oxidation degree of HA,the ability to improve aromaticity is not good.It is proved that the application of HCS can better improve the degree of oxidation and condensation of HA,and the degree of aromatization is also deepened.The relative intensity of 1620 cm-1absorption peak has also been improved,which increased by 7.74%.I2920/1620shows a downward trend.Both HCS and Bc showed three obvious fluorescent groups in the fluorescence spectrum analysis.Compared with CK,the relative intensities of peak A and peak C are higher,showing higher aromaticity.The average exothermic range of the four treatments is 465.3℃～576.0℃.Among them,HCS and Bc treatments showed better thermal stability,and their high temperature/medium temperature exothermic ratio showed a decreasing trend.The results showed that the aromaticity/aliphatic property of soil HA tended to be stable.Compared with CK,the weight loss high/medium ratio of HCS is also higher,which indicates that it has stronger thermal stability.Among the three materials,HCS is the best in the overall effect on soil available nutrients,maize growth and yield improvement.Although Bc treatment had the best effect on soil available potassium content at two years,its effect on soil alkali-hydrolyzable nitrogen and available phosphorus was significantly weaker than HCS.To sum up,compared with CS and Bc,HCS is more helpful to the accumulation and transformation of SOM.Improve the composition of soil humus and improve the aromaticity and stability of HA,increase soil available nutrients and maize yield.Therefore,after the corn straw is decayed,it is applied.It will be an effective way to increase the conversion rate of soil organic matter,improve HA structure and increase maize yield. |
PDF Full Text Request