Oxygen Mass Transfer Characteristics Of Aeration Drip Irrigation And Its Effects On Pepper Growth And Soil Environment In Root Zone

In agricultural production,irrigation provides water to crops while driving air in the pores of the soil,hindering the exchange of oxygen between the atmosphere and the soil,reducing the oxygen content of the soil,and prone to low oxygen in the anaerobic environment of the crop root zone for a long time.Stress is not conducive to the normal growth and development of crops.Aeration drip irrigation is an efficient and water-saving irrigation technique that uses aeration equipment for aeration and aeration to coordinate the delivery of oxygen-enriched water to the root zone of the crop.Aeration drip irrigation effectively improves soil aeration by regulating soil water and gas environment.However,the dissolved oxygen limitation of the irrigation water and the low efficiency of oxygen mass transfer during the aeration process have become the main bottleneck for the promotion of aeration irrigation technology.How to regulate the water supply system to increase the dissolved oxygen concentration and oxygen mass transfer efficiency in irrigation water has become the key to the promotion of aeration irrigation technology.In this study,water-fertilizer-gas coupled automatic irrigation equipment was used for aeration,and the effects of different pressures and surfactant concentrations on dissolved oxygen concentration and oxygen mass transfer efficiency during cyclic aeration were studied,and the appropriate aeration parameters in the circulating aeration system were clarified.Through the pot experiment,the response of crops to cyclic aerated drip irrigation under different oxygen concentration and different soil conditions was studied,and the high-efficiency irrigation system of cyclic aeration drip irrigation was obtained,which provided theoretical guidance for the scientific application of aerated drip irrigation technology.The main conclusions of the trial were as follows:(1)In the circulating aeration system,the saturated dissolved oxygen increased significantly by more than 36 % with the increase of pressure(P<0.05).Compared with the fresh water condition,the addition of the active agent significantly increased the saturated dissolved oxygen value(P <0.05).The increase of pressure increases the oxygen mass transfer coefficient by more than 17 %,and the increase of active agent concentration increases the oxygen mass transfer coefficient by more than 52 %.(2)The plant height and stem diameter of the three soil treatments all showed an upward trend.Compared with CK,except for the seedling stage,the plant height and stem diameter of the three soils treated with 40 mg/L oxygen concentration were significantly increased(P<0.05).Compared with CK,the plant height of 40 mg/L plus oxygen concentration in the three soils increased significantly by more than 20 %(P<0.05),and the stem thickness increased by more than 26 %(P<0.05).(3)The soil respiration rate,photosynthetic rate and transpiration rate of the three soils increased first and then decreased,and the peaks appeared in the fruit expansion period.In addition to the seedling stage,the soil respiration rate of the three soils treated with 40 mg/L oxygen concentration was always the largest,and the soil respiration rate treated with CK was the smallest.During the whole growth period of pepper,the soil respiration rate of YC-40 treatment was up to 40.38 %(P<0.05)compared with YC-CK treatment;the soil respiration rate of SCL-40 treatment was up by 36.2 % compared with SCL-CK treatment(P<0.05);HL-40 treatment showed a maximum increase in soil respiration rate of 42.42 %(P<0.05)compared with HL-CK treatment.The photosynthetic rate of YC-40 treatment was 31.14 % higher than that of YC-CK treatment(P<0.05).The photosynthetic rate of SCL-40 treatment was 31.47 % higher than that of SCL-CK treatment(P<0.05).HL-40 treatment was better than HL.The photosynthetic rate of pepper treated with HL-CK increased by 34.84 %(P<0.05).Compared with YC-CK,the transpiration rate of YC-40 treatment increased by 55.28 %(P<0.05).The transpiration rate of SCL-40 treatment was 61.3 % higher than that of SCL-CK treatment(P<0.05).The transpiration rate of HL-CK treatment increased by 47.65 %(P<0.05).(4)The yield of the three soils treated with 40 mg/L oxygen concentration was always the largest.There was no significant difference in the yield between SCL-40 treatment and SCL-15 treatment,and there were significant differences between the other treatments(P<0.05).The yield of YC-40 treatment was significantly higher than that of YC-CK treatment by 40.71 %(P<0.05).The yield of SCL-40 treatment was significantly increased by 21.06 %(P<0.05)compared with SCL-CK treatment.The yield of HL-40 treatment was higher than that of CK.Significantly increased by 37.11 %(P<0.05).The quality of pepper after aeration drip irrigation was also improved,especially at 40 mg/L oxygen concentration.(5)Aeration drip irrigation significantly increased the microbial population and soil enzyme activity in the root zone of pepper.The soil enzyme activities of the three soils treated with 40 mg/L oxygen concentration were higher than 15 mg/L oxygen concentration treatment and control treatment;the microbial quantity also showed 40 mg/L oxygen concentration>15 mg/L oxygen concentration>CK.The dissolved oxygen and oxygen mass transfer coefficients during the comprehensive aeration process are recommended to be a suitable aeration combination with a pressure of 1.5 bar and an active agent concentration of 5 mg/L.In the pot experiment,the yield,quality,growth index and physiological index of pepper were compared comprehensively,and the effect of YC-40 treatment on pepper was the most significant.