Mechanism Of Aerated Irrigation To Enhance Nitrogen Uptake And Yield Of Facility Vegetables

Aerated irrigation has a significant contribution to increasing the yield and efficiency of vegetable facilities.However,the oxygen requirements of different vegetables have not been reported,and too high or too low aerated amounts may restrict the growth of vegetable roots and reduce the uptake of water and fertilizer,resulting in reduced vegetable yields.In order to obtain the appropriate number of aerated vegetables and to analyse the changes of root morphology-soil environment-soil microbial community,the mechanism of increasing the yield and efficiency of vegetables with the appropriate number of aerated vegetables is of great significance for the sustainable development of high yield and high efficiency of greenhouse crops.In this study,three types of vegetables,namely tomato,pepper and cucumber,were planted in buckets and plots to investigate the effects of different aerated conditions on the growth,root morphology,soil environment（soil aeration,soil physicochemical parameters）and nitrogen uptake and yield of vegetables.The analysis of soil bacterial community structure in terms of bacterial community structure and diversity,symbiotic network and other aspects,reveals the mechanism of"aerated irrigation-root structure and morphology-soil microenvironment-nitrogen uptake-yield."The main findings include:（1）Aerated irrigation significantly improves the yield,dry matter accumulation and photosynthetic characteristics of greenhouse tomatoes.This enhancement was most pronounced when aerated levels reached 15 mg/L,with tomato yields increasing by 29.73%over the control at the same level of nitrogen application.Cumulative nitrogen uptake and fertiliser bias productivity of tomato under aerated irrigation increased by 53.06%and 46.75%,respectively,compared to the control（P<0.05）.The path coefficient for the effect of aerated irrigation on nitrogen uptake was0.969.The present study showed that the application of 240 kg/hm² of nitrogen at 15mg/L of aerated irrigation significantly increased tomato yield,dry matter accumulation and physiological characteristics and nitrogen uptake and utilisation at all fertility stages.（2）Aerated irrigation significantly increased root dry weight,root volume,root surface area,BRIX,soluble protein,SAT,yield and IWUE in pepper.It was optimal at 15 mg/L of aerated volume and 0.8 times the crop-evaporation dish coefficient,significantly increasing 13.63%,59.47%,61.67%,29.49%,75.24%,68.10%,42.74%,and 42.88%,respectively（P<0.05）.Based on the correlation analysis and principal component analysis,the root morphology,yield,IWUE,and fruit quality were considered together,and root morphology had a significant positive correlation on crop yield,quality and a significant contribution of root morphology to pepper yield and quality under aerated irrigation was obtained.The experiment concluded that the triple requirements of quality improvement,yield increase,and water saving could be met at an aerated rate of 15 mg/L and an irrigation rate of 0.8 times the evaporation dish coefficient of the crop.（3）The suitable amount of aerated air will improve the aeration of the cucumber soil,promote root growth and increase yields.From the typical correlation and gray correlation analyses,soil DO,and respiration rate were the dominant factors for soil aeration indexes.Root length,root surface area,root volume,root tip number,fork number,and root dry weight were the dominant factors of root morphological indexes.The main correlation indexes to enhance cucumber yield were soil DO,soil respiration rate,root length,and root tip number,and the correlation coefficients were 0.817,0.806,0.702,and 0.682,respectively.The combined obtained soil DO and root tip number had the most significant influence on cucumber yield increase.The correlation coefficient between each index and yield and nitrogen uptake was highest when the aerated amount was 20 mg/L,and the yield and economic benefit of cucumber were highest at this time,with 53.04 t/ha.Compared with the aerated amount of 10 mg/L and conventional subsurface drip irrigation,the yield increased by4.27%and 7.86%,respectively（P<0.05）.The economic efficiency increased by 7.42%（P<0.05）compared to conventional subsurface drip irrigation.（4）Aerated irrigation increases the nitrate and ammonium nitrogen and urease activity of pepper soils,reduces soil p H and significantly improves yields and economic efficiency.At an aerated level of 15 mg/L,the most significant increase in root morphology was observed at the fruit expansion to ripening stage and the highest pepper yield of 3.05 t/hm²,which was 15.72%and 37.00%higher（P<0.05）compared to the irrigated treatment with and without aerated level of 25 mg/L,respectively.Typical correlation analysis and grey correlation analysis revealed that root volume,root surface area,nitrate nitrogen,root vigour,fork number,root dry weight and yield were highly correlated,and nitrate nitrogen had the highest correlation coefficient with soil environment and best characterised soil environmental conditions,while root volume,root surface area,fork number,root dry weight and root vigour were the dominant factors in root morphological indicators of pepper and best characterised root growth conditions.Aerated irrigation significantly improved the economic efficiency and nitrogen uptake of pepper,and the best benefit was achieved at an aerated rate of15 mg/L,with an increase of 74.19%（P<0.05）compared to the non-aerated treatment.（5）Aerated irrigation can significantly increase the content of soluble organic matter（DOM）fractions,bacterial community abundance and diversity in cucumber and pepper crops.From the parallel factorial analysis,the cucumber test yielded three components:C1（humic acid）,C2（amino acid or protein）,and C3（terrestrial humus）,all of which were highest at 20 mg/L.The pepper test（2）yielded two components:C1（UV humic acid-terrestrial plant-UVC）and C2（humus-rich acid-small molecule amino acids）,both of which were highest at the gas increase of 15 mg/L.High-throughput sequencing showed that suitable gas consumption could promote the relative abundance of Actinobacteria,Bacteroidetes,Firmicutes,α-Proteobacteria,and Clostriobacteria and reduce the relative abundance of Proteobacteria andγ-Proteobacteria spp.Aerated treatment can significantly improve the Rhizosphere’s Shannon and Pielou＿e index of soil bacteria.The results of the NMDS analysis indicated significant differences between different gas volumes.Redundancy analysis of the cucumber test showed that root morphology（root length,root dry weight,root volume,root surface area,apical number,and fork number）and soil environment（Rs,DO,C1,C2,C3,and NO₃^--N）were closely related to bacterial community structure distribution.DOM components were positively correlated with the most beneficial bacteria in the top ten phylum level abundance.Redundancy analysis of the pepper test showed that root morphology（root length,root dry weight,root volume,root surface area,apical number,bifurcation number,and root vitality）and soil environment（UA,C1,C2,NH₄⁺-N,and NO₃^--N）were closely related to the distribution of bacterial community structure,and the tips and NO₃^--N content was crucial indicators.（6）Aerated irrigation increases the complexity between bacterial community species.Analysis of the bacterial molecular symbiotic network showed that the appropriate aerated volume treatment increased the beneficial phylum Dependentiae,Cyanobacteria,Deinococcus-Thermus,Firmicutes and Planctomycetes compared to the non-aerated treatment,and correlated higher with Actinobacteria,Nitrospirae and Gemmatimonadetes.In addition,the number of network nodes,connecting lines,and modules suitable for aerated irrigation treatment is lower than that of conventional underground drip irrigation treatment.However,the number of modules and modules is the highest.In conclusion,aerated irrigation changes the structure of the symbiotic network according to bacterial communities.So appropriate gas to facilitate vegetable root form and soil environment have a significant effect,and root form and soil environment facilities crop nitrogen absorption.Yield is also inseparable,showing that aerated irrigation,in addition to improving the root area oxygen environment,its characteristics can also directly affect the crop yield,nitrogen absorption,and soil microbial community structure.However,the promotion of plant growth was not significantly enhanced by the excessive oxygen addition concentration.