Study On Greenhouse Vegetable Growth And N₂O Emission From Soil Under Water-Fertilizer-Air Coupled Drip Irrigation

Water-fertilizer-air coupled drip irrigation is a new drip irrigation technology.It has the advantages of drip fertigation and aerated drip irrigation.Water-fertilizer-air coupled drip irrigation can quantitatively deliver oxygen,water and fertilizer to the root zone,which relieve rhizosphere dysfunction,promote crop water and fertilizer absorption,thus increasing crop yield and fruit quality.Presently,the laws governing vegetable growth,nutrient utilization and soil N₂O emissions under water-fertilizer-air coupled drip irrigation are still unclear.In this study,tomato and pepper were used as experimental crops,and different irrigation amounts were set?the low and high irrigation volumes during tomato season are I₁and I₂ respectively,the low and high irrigation volumes during pepper season are I₃ and I₄respectively?,and aeration treatments?control C and aeration treatment A?and fertilization amount?the low nitrogen and normal nitrogen during tomato season are N₁ and N₂,respectively,and low nitrogen and normal nitrogen during pepper season are N₃ and N₄,respectively?.We systemly monitore the soil aeration index?filled water porosity WFPS,oxygen diffusion rate ODR and redox potential Eh?and soil nutrient index?nitrate nitrogen NO₃^--N and ammonium nitrogen NH₄⁺-N?,yield,quality indicators?Vitamin C and soluble protein content?,water and fertilizer use indicators?irrigation water use efficiency WUE and nitrogen absorption efficiency UPE_N?.Soil N₂O emission indicators?N₂O emission flux and total N₂O emissions?,etc.Through the analysis of the characteristics of crop growth and water and fertilizer utilization under the condition of water-fertilizer-air coupled drip irrigation,the effects of water-fertilizer-gas coupled drip irrigation on crop growth are explored.The soil N₂O emission and its influencing factors are studied to provide scientific basis for the reduction regulation of N₂O emissionfrom soil.Main conclusions are given as below.?1?Water-fertilizer-air coupled drip irrigation changed the soil aeration in the root zone.The increase of irrigation amount reduces the average value of soil ODR and Eh,that is,the increase of irrigation amount leads to the deterioration of soil ventilation.Compared with the control,the aeration treatment increase the soil ODR and Eh,i.e.,the aeration treatment improve the soil aeration.?2?Water-fertilizer-air coupled drip irrigation changes the soil nutrient status in the root zone.The increase of irrigation amount reduces the mean NH₄⁺-N and the mean value of NO₃^--N.The high rate of nitrogen application increases the soil NH₄⁺-N and NO₃^--N.Compared with the control,the aeration treatment reduces the NH₄⁺-N and soil NO₃^--N.?3?Aeration treatment,the increase of irrigation amount and nitrogen application rate improve the yield and fruit quality of vegetables.During tomato growing period,the yield of I₂ increase by 41.14%compared with I₁;the yield of N₂ increased by 41.32%compared with N₁;the yield of aeration treatment increase by 23.19%compared with the control.During pepper growing period,the yield of I₄ increase by 25.24%compared with I₃;the yield of N₄increased by 29.04%compared with N₃;the yield of aeration treatment increase by 18.18%compared with the control.?4?The increase of irrigation amount reduces WUE and increases UPE_N.The high nitrogen application increases WUE and reduces UPE_N.The aeration treatment increases WUE and UPE_N.?5?Aeration treatment,the increase of irrigation amount and nitrogen application rate increased the total N₂O emission of soil during the growth period.Under the tomato-pepper cropping system,the total N₂O emission increased by 39.70%under high water condition,65.55%under normal nitrogen condition and 24.56%under aeration condition compared with the control.?6?The structure equation model of soil N₂O emission flux was used to analyze the results,soil temperature NO₃^--N content,NH₄⁺-N content,WFPS and ODR are important factors influencing soil N₂O emissions.?7?Comprehensive reference to vegetable yield and total N₂O emission during growth period.I₁AN₂ is a suitable drip irrigation scheme in tomato experiment.I₄AN₃ is a optimal suitable scheme during pepper growing season.The results in these experiments clarifies the effect of water-fertilizer-air coupled drip irrigation on the growth of vegetables,and provides a scientific basis for the regulation of soil N₂O emission reduction in greenhouse.