| As the most widely used solid fumigant and the most frequently used fumigant in China,Dazomet has the advantages of convenience and safety.The fumigation of dazomet leaf significantly improved crop growth and nitrogen absorption,but the mechanism was not clear.Combined with laboratory and field experiments,the red soil of Yunnan and Beijing tidal soil were used as experimental soil,and tomato,pepper and tobacco were selected as experimental subjects.By means of metagenomic sequencing analysis and eukaryotic reference transcriptome sequencing analysis,the nitrogen absorption regularity and its influencing mechanism of crops after fumigation of dazomet leaf were revealed.1.Control effect of fumigation on soil-borne diseasesThe indoor fumigation results showed that the control efficiency of fumigation on Fusarium and Phytophthora was more than 89% in the two soils tested.The results of field experiments showed that fumigation of dazomet was effective in controlling soil-borne diseases in tomato greenhouses,including Fusarium spp.,Phytophthora spp.The control effect was95.44%-99.81%,and maintained excellent control effect after fumigation 45 and 90 days.2.Effects of fumigation on nitrogen uptake of cropsFumigation of dazomet significantly improved the physiological indexes of tomato,pepper and tobacco and the dry matter quality of root,stem and leaf,decreased the percentage of total nitrogen in each part of the crop,and significantly promoted the nitrogen accumulation of the crop.In the Yunnan red soil,the nitrogen accumulation of tobacco root,stem and leaf on the50 th day was increased by 2684.22%,1056.04% and 1153.31%,respectively,compared with the control group.In the Beijing tidal soil,the nitrogen accumulation of each part was increased by96.26%,44.97% and 45.28%,respectively.The results of inorganic nitrogen determination showed that Mianlong fumigation significantly reduced the nitrate nitrogen content of tobacco,and decreased by 70.86%-90.21%,37.45%-40.18% and 30.20%-46.09% in all parts of tobacco roots,stems and leaves,respectively,significantly increased the ammonium nitrogen content.Roots,stems and leaves increased 50.69%-42.34%,31.91%-94.82% and 25.43%-53.95%,respectively.3.Mechanism of nitrogen absorption promoted by fumigation of dazomet leafIn terms of rhizosphere nitrogen supply,the fumigation of dazomet rise significantly inhibited the nitrification rate of soil and promoted denitrification.The nitrate nitrogen supply rate of roots decreased by 45.16-82.47%,and the ammonium nitrogen supply rate increased by250.71-807.12%.After fumigation,the abundance of Proteus,greencurve,Bacillus,Firmicutes and Bacteroides increased significantly,while the abundance of actinomyces,Acidobacterium and pontoides decreased.nar Y fumigation significantly increased the abundance of nitrogen fixing gene nif D,nitrification genes nar H,Nary,nxr B,and denitrification genes nar G,nar Z,nir S,nir K,nor B,nor Z,while significantly decreased the abundance of nitrogen fixing gene nif K and nitrification function gene amo A.Nitrogen metabolism gene expression: After fumigation,Miamon significantly promoted the expression of nitrate nitrogen absorption functional genes NPF5.5,NPF5.6,NPF6.3,NPF6.4,NRT 3.1 and ammonium nitrogen absorption functional gene AMT1.1 in root and leaf of tobacco.The expression of GSN-1 gene encoding glutamine synthetase was significantly up-regulated in roots and down-regulated in leaves.After fumigation,glucosaldosan-related metabolism and biometabolic processes in cell wall were significantly enriched in tobacco roots,photosynthesis and nuclear-related functions in leaves were significantly enriched.In terms of key enzyme activities of nitrogen metabolism,nitrite reductase activities in all parts of roots,stems and leaves of tobacco were significantly increased after fumigation in dazomet leaf,leaf and stem,glutamine synthetase activities in root at early growth stage and glutamate synthetase activities in leaf and stem at late growth stage were significantly increased.4.Field experiment on nitrogen uptake of crops by fumigation of dazomet LoonField results showed that fumigation of dazomet rose significantly promoted tomato growth and nitrogen accumulation.Ammonium nitrogen content in roots,stems and leaves increased by103.95%,51.20% and 54.22%,and nitrate nitrogen in roots and leaves decreased by 45.51% and38.01%,respectively,resulting in a 4.16% increase in nitrogen use efficiency in tomato fields(P<0.05). |
