Water,Fertilizer And Gas Coupling For Greenhouse Tomatoes To Improve Quality And Reduce Emissions Model Research

Aerated irrigation can improve soil aeration and solve the problem of hypoxia in soil under water saturation for a long time,promote crop growth and development,increase crop yield,and improve water and fertilizer utilization efficiency.However,aerated irrigation is also accompanied by an increase in greenhouse gas emissions.At present,the influence mechanism of soil factors on greenhouse gas emissions is still unclear,and there is a lack of comprehensive evaluation of tomato yield,quality and greenhouse gas,so it is necessary to put forward a better irrigation model with better yield,emission reduction and quality.In this study,tomato was used as the test crop.Two irrigation levels,I1 and I2（deficit irrigation and full irrigation,corresponding crop-dish coefficient Kcp were 0.8 and 1.0）,and two nitrogen application levels,F1 and F2(low nitrogen and high nitrogen,corresponding nitrogen application amounts of 180 kg·hm^-2 and 240 kg·hm^-2),were set.There were two aeration levels A1 and A2（1 and 2 times air,respectively,and the intake volume of 1 times air irrigation water accounted for about 17%of the irrigation water）,and the two nitrogen application levels under the condition of full irrigation without aeration（CK for unaerated irrigation）were taken as the control.There were 10 treatments in total.The effects of different water,fertilizer and gas treatments on soil environmental factors（soil moisture,soil temperature,soil mass fraction of nitrate nitrogen,the number of nitrifying bacteria and denitrifying bacteria）,greenhouse gas emissions,tomato biomass,root index,yield,quality and water and fertilizer utilization efficiency were studied,and the influence mechanism of soil environmental factors on greenhouse gas emissions was analyzed.Considering the aspects of increasing tomato yield,improving fruit quality,reducing greenhouse gas emission and improving water and fertilizer utilization efficiency,a comprehensive evaluation was made on each tomato index,and the best irrigation mode of increasing yield,reducing emission,improving quality and improving water and fertilizer utilization efficiency was proposed.The main conclusions are as follows:（1）The influences of different water,fertilizer and air treatments on soil environmental factors were clarified.Under the condition of the same nitrogen application and aeration level,the irrigation level increased,soil water-filled porosity（WFPS）increased,nitrate nitrogen（NO₃^--N）mass fraction,the number of nitrifying bacteria and denitrifying bacteria increased,and soil temperature decreased.Under the condition of the same irrigation and aeration level,nitrogen application level increased,WFPS decreased,soil temperature,NO₃^--N content,the number of nitrifying bacteria and denitrifying bacteria increased.Compared with control treatment（CK）,aerated irrigation（A1 and A2）and aerated irrigation increased the WFPS,the content of NO₃^--N and the number of nitrifying bacteria,and the number of denitrifying bacteria.For soil temperature,compared with control treatment,A1 and A2 treatment will reduce soil temperature,but the increase of air injection level will increase soil temperature,that is,CK>A2>A1.（2）The effects of different water,fertilizer and gas treatments on soil greenhouse gas emissions and soil environmental factors affecting greenhouse gas emissions were clarified.The level of irrigation,nitrogen application and aeration remained unchanged,and the increase of any factor level would increase the emission of soil CO2 and N2O.Soil CH4emission was increased with the increase of irrigation level,and decreased with the increase of nitrogen application level and aerated irrigation.When soil temperature is low（before 37 days after transplantation）,CO2 and N2O emissions will be inhibited.At this stage,the effects of WFPS and other factors are covered by the effects of soil temperature.After removing the data at this stage,soil CO2 and WFPS showed a linear positive correlation（P<0.01）.When soil temperature was less than 26℃and greater than 26℃,there was linear positive correlation and linear negative correlation with soil CO2 emission flux,respectively（P<0.01）.WFPS and soil temperature are the main controlling factors affecting CO2 emission,and coordinate with each other to influence CO2 emission.Soil N2O emission flux was positively correlated with WFPS（P<0.01）.N2O emission was also affected by growth stage.From seedling stage,flowering and fruiting stage to fruit expansion stage,soil temperature was positively correlated with soil N2O emission flux（P<0.01）.At the maturity stage,soil temperature was negatively correlated with soil N2O emission flux（P<0.01）,and NO₃^--N was positively correlated with soil N2O emission flux（P<0.01）.WFPS,soil temperature and NO₃^--N were the main controlling factors affecting N2O emission,and NO₃^--N had the highest influence.The correlation between WFPS and CH4 emission flux was significantly positive（P<0.01）.（3）The effects of different water,fertilizer and gas treatments on crop growth,and then on tomato yield and quality,as well as on global net warming potential（NGWP）,greenhouse gas emission intensity（GHGI）,irrigation water use efficiency（IWUE）and nitrogen use efficiency（NUE）were clarified.Under the coupling model of water,fertilizer and air,the increase of irrigation,nitrogen application and aeration level promoted the growth of crop root,and then increased the yield of tomato.Different treatments of water,fertilizer and air improved fruit quality,the increase of irrigation level reduced tomato quality indexes,the increase of nitrogen application level increased tomato quality indexes,aerated irrigation reduced organic acid content,and increased lycopene,Vc,soluble solid and soluble sugar.NGWP was significantly increased by irrigation level,nitrogen application level and aeration level（P<0.05）,and GHGI was increased by irrigation level and nitrogen application level.Compared with CK treatment,the change of GHGI in different aeration levels is different.A1 aeration level will reduce GHGI,while A2 level will increase GHGI,as shown in A2>CK>A1,indicating that A1 aeration level will reduce greenhouse gas emission per unit mass of tomato.（4）From the aspects of increasing tomato yield,improving fruit quality,reducing greenhouse gas emissions and improving water and fertilizer utilization efficiency,comprehensive evaluation of tomato treatment was conducted based on tomato yield,quality,NGWP,GHGI,IWUE and NUE indexes.The results showed that A2F2I1（Kcp=0.8）treatment with 240·kg·hm^-2 nitrogen application rate had the highest comprehensive score,which could take into account the requirements of yield increase,emission reduction,quality improvement and water and fertilizer utilization efficiency of tomato,and was the best irrigation mode for greenhouse tomato with water and fertilizer.