The Effects Of The Corn Straw And Its Humified And Carbonized Materials Returning To The Black Soil On The Humus

The output of crop straw is huge in China,but the straw utilization rate is low,a large number of straw were burned and idle.For the purpose of improving the soil properties by using crop stalks rationally,the domestic and foreign scholars have done a great deal of research on straw return to the soil.However,which returning is the best way to improve soil properties and improve crop yield has not been compared and studied under the same conditions.Therefore,this study through the laboratory simulation and pot experiment conducted to investigation the soil humus composition,humic acid?HA?structure and corn growth and yield under applications of three different forms of corn straw?original,humified and carbonized?to the black soil at equal mass of carbon.Four treatments included non-organic materials amendment as control?CK?;corn straw?CS?,humified corn straw?HCS?and biochar?Bc?,respectively.The composition of humus consists of water soluble substance?WSS?,extracts of humus?HE?,fulvic acid?FA?,humic acid?HA?,and humin?HM?.The HA structure was determined by elemental composition,infrared spectrum?IR?,differential thermal analysis?DTA?and solid-state ¹³C nuclear magnetic resonance?NMR?.Calculation of yield by ear row number,row grain number and 100 grain weight.Results showed that:1.Comparison of the structural properties of corn straw and its humified and carbonized materials.The chemical structure of corn straw has changed greatly after humification and carbonization,especially after the carbonization of high temperature pyrolysis,the carbon content of biochar has obviously increased,and the content of O and H has decreased.The content of C and H was reduced after the humification of straw,and the content of N and O was increased,and the ratio of C/N was smallest,and the O/C ratio increased.In the structure of corn straw and humified corn straw,there are more aliphatic C-H and C-O,with fewer aromatic chain hydrocarbons.However,the structure of biochar contains more aromatic C=C structure and less aliphatic structure.2.Different organic materials amendment are beneficial to improve soil organic carbon?SOC?content.All the treatments with organic material amendment are beneficial to improve soil organic carbon?SOC?content,and the changes of SOC content in different culture periods and the pot experiment were similar,all of which were shown as Bc>HCS>CS>CK.Compared with CK,the content of SOC in Bc,HCS and CS were significantly increased by 14.66%and 10.51%,10.25%and 8.30%,5.90%and 5.12%after culturing 90d and 180d.After 360d of cultivation,the content of SOC in Bc,HCS and CS were significantly increased by 13.36%,10.02%and6.21%,with significant differences between all treatments.The soil organic carbon content of all treatment with organic material amendment were increasing after two years of pot experiment.In the first year,the SOC content of Bc,HCS and CS treatments had significantly increased by 20.59%,18.12%and 11.08%,respectively.In the second year,the SOC content of Bc,HCS and CS increased by 18.20%,17.36%and 1.45%respectively,and the difference between Bc and HCS was significant,and the difference in CS treatment was not significant.3.Different organic materials amendment to improve the composition of humus.Bc,HCS and CS treatments are beneficial to increase the content of organic carbon of humus and increase the degree of soil humification?PQ?,among which the most significant was Bc treatment,followed by HCS and CS treatments.After 90d of cultivation,the PQ values of Bc,HCS and CS treatment were increased by 12.11%,7.77%and 4.77%respectively.After180d of cultivation,Bc,HCS and CS treatment were increased by 11.98%,9.11%and 5.47%respectively.And after 360d cultivation,the PQ values increased by 11.96%,10.71%and6.43%of Bc,HCS and CS treatment,respectively.The PQ values of the pot experiment were increased in 2 years,and Bc,HCS and CS treatment increased by 5.35%and 11.30%,3.99%and 7.00%,2.28%and 4.61%respectively.4.Different organic materials have different influences on humus structure.The ratio of?O+S?/C of all the treatments were less than that of CK,the relative strength of the HA absorption peak at 1 720 cm^-1 were decreased,and the carbonyl group decreased,indicating that the addition of organic materials reduced the oxidation of HA molecules.The ratio of H/C and 2 920/1 620 of CS and HCS treatments had increased and the exothermic heat ratio of high temperature/moderate temperature and weight loss had significant decreased,and the ratio of aliphatic C/aromatic C had increased.Bc treatment with the opposite.The results indicated that corn straw and humified corn straw applications to the soil are facilitated to simplify soil humic structure by decreasing HA condensation,aromaticity,hydrophobicity,and at the same time increasing HA molecular aliphaticity.In contrast,Biochar application to the soil is helpful to promote HA molecular condensation and aromaticity and the soil HA molecular tends to be complicated and stability.The?lgK values of HA and FA of different culture stages and pot experiment of two years had shown as HCS>CS>CK>Bc.The results illustrates that corn straw and humified corn straw applications to the soil are facilitated to develop in the direction of simplification of HA and FA molecular.5.Different organic materials amendment is beneficial to corn growth and increase corn yield.After two years of pot experiment,the corn plant of Bc treatment was the highest,followed by HCS,and CS treatment was slightly higher,but the difference was not significant compared with CK.After two years pot experiment,the corn yield with organic materials had significantly increased,which was shown as Bc>HCS>CS>CK.Adding organic material for two years had no effect on the number of row of ears,but the number of grain and 100 grain weight increased.The results showed that the effect of adding organic materials on corn yield was mainly reflected in increasing the number of row grains and the full extent of grain.Therefore,the addition of biochar is more beneficial to corn growth and higher corn yield.