| The decomposition process of crop straw returning to the field have both short-term and long-term effects on the physical and chemical characteristics of soil and the growth of crops.It is a key problem to improve the technical efficiency of crop straw returning,it alleviates the adverse effect of straw decomposition on the growth of crop seedlings.Soil carbon-nitrogen ratio is an important factor affecting straw decomposition and soil mineral nutrient accumulation,conversion and absorption.Regulating soil nutrient and soil microorganism,enzyme activity,and straw decay resistance and nutrition absorption effect on crop system as the breakthrough point in this study,this study of corn straw returned with humic acid and nitrogen fertilizer included soil microbial components,mineral elements content,enzyme activity,and the resistance of corn plant system,nutrient absorption and the influence of growth.The results showed that,1.The root length and shoot length of germinated maize seeds cultured with straw decomposition solution decreased contrasted control by 57.3 % and 37.6 % respectively.The root weight and shoot weight were significantly reduced by 35.0 % and 18.8 %,respectively.Compared with the control group,the root-shoot ratios were significantly reduced by 25.2%.The activity of phenylalanine ammonia-lyase(PAL)and peroxidase(POD)were decreased when adding straw and humic acid leaching,and the superoxde dismutase(SOD)activity of bud was increased by 93.8% compared with that of straw leaching alone.The content of malondialdehyde(MDA)in shoots and roots were significantly reduced by 26.8 % and 32.6 %,respectively,and by 50.7 % and 56.9 %,respectively,compared with the control.The root length and shoot length were significantly increased by 40.0 %and 40.6 %,respectively,and significantly decreased by 40.2 % and 12.3 %,respectively,compared with the control.The root weight and shoot weight increased by 46.2 % and 38.5 % respectively,and the shoot weight increased by 12.5 % compared with the control.Compared with the single straw leaching treatment,the root crown reduced by 14.1 % and 35.8 % respectively.2.The activity of superoxide dismutase(SOD)and peroxidase(POD)significantly reduced,and the accumulation of superoxide anion radical(SAR)significantly increase malondialdehyde(MDA)content and PAL activity by straw application at elongation stage of maize,while the application of nitrogen fertilizer or humic acid resulted in further decrease of SOD and POD activity and the increase of MDA content.Straw application had little effect on the antioxidant system of tasselingmaize,and nitrogen fertilizer significantly improve the POD activity and reduce the degree of membrane lipid peroxidation.Straw application decreased PAL activity by 26.8%,however,humic acid,nitrogen fertilizer and mixed application significantly increased PAL activity by 69.3%,60.1%and 76.2%,respectively.The increase of systemic resistance promoted the dry matter accumulation of plants,while straw application decreased by 28.3%,however,humic acid,nitrogen fertilizer and mixed application significantly increased dry weight by 24.4%,59.2% and 28.2 %,respectively.3.Under the condition of straw application,total nitrogen content increased by 23.8 %,total potassium content increased by 19.48 % and total phosphorus content decreased by 18.1 %.The total potassium content of humic acid plants increased by 19.48 % on average.The effect on the content of magnesium and calcium was not significant.The effects of nitrogen and humic acid on total nitrogen and total phosphorus content of maize in tastasing stage were not significant,the total potassium content of maize increased by 39.5%,and the magnesium and calcium content of maize decreased slightly,but the difference was not significant.4.The soil alkali-hydrolyzed nitrogen content in the jointing stage and tastasing stage of maize increased because of straw application,and the soil with nitrogen treatment had higher alkali-hydrolyzed nitrogen content,while the soil with humic acid treatment had no significant difference from the control.The content of available phosphorus and available potassium in the soil during tasmaning stage could be significantly increased by straw fertilization,while the content of available phosphorus and available potassium in the soil could be increased by nitrogen or humic acid fertilization.The content of available phosphorus in the soil increased by nitrogen and humic acid fertilization,while the content of available potassium in the soil was not significantly different from that in the control group.5.The activity of soil urease decreased 17.5 % and 20.2 %,respectively,in 5 cm-10 cm soil and10 cm-15 cm soil,and soil sucrase activity decreased 30.0 % by average.Simultaneously,the activity of acid phosphatase increased 16.1 % and 19.7 %,respectively,in 5 cm-10 cm soil and 10cm-15 cm soil.The application of humic acid and nitrogen improved the activity of soil acid phosphatase to different degrees,especially the application of nitrogen.6.The amount of actinomycetes and fungi decreased,but the amount of bacteria did not increase,which affected the growth of soil microorganism.The application of nitrogen fertilizer or humic acid reduced the amount of bacteria and actinomycetes,but had no significant effect on the fungi.Therefore,the total soil microorganisms significantly reduced by 29.3% and 42.7%,respectively,and the mixed application of nitrogen fertilizer and humic acid significantly reduced by 63.2%.Because humic acid and corn straw have a high C/N ratio,increasing nitrogen application level and maize straw with humic acid were an important supporting measure for applying straw returning technology. |
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