Effects Of Root Zone Oxygen Supply And Nitrogen Application On The Growth Of Greenhouse Tomato

Traditional irrigation methods will displace gases in the soil after irrigation,causing root zone hypoxia,which is not conducive to crop growth and yield improvement.Oxygenated irrigation is a new irrigation technology that fully dissolves and combines water and oxygen and directly transports them to the root zone of crops.It can effectively improve the efficiency of crop water and fertilizer utilization and is of great significance for the development of facility agriculture.At present,research on the changes in crop photosynthetic physiological activities under oxygenated irrigation still needs to be explored,and the process of improving crop yield and quality is not clear.In addition,there may be a strong interaction between oxygen and nitrogen application,and the impact of nitrogen oxygen coupling on tomato growth at different growth stages needs to be further studied in detail.Therefore,this article takes facility tomatoes as the experimental crop and uses root zone oxygenation irrigation method to set up three oxygenation levels A0（no oxygenation）,A1(15 mg·L^-1),A2(30 mg·L^-1),and three nitrogen application levels N1(160 kg·hm^-2),N2(240 kg·hm^-2),N3(320kg·hm^-2).By analyzing the effects of different combinations of oxygen and nitrogen application on soil environmental changes,tomato growth and development,root morphology,photosynthetic performance,and nitrogen absorption and utilization efficiency,this study aims to explore the reasons for the increase in tomato yield and quality under oxygen irrigation,in order to obtain an oxygen and nitrogen application combination for high-quality and efficient production of greenhouse tomatoes.The following main results were obtained:（1）Root zone oxygenation improved the soil oxygen environment.In a irrigation cycle,the soil oxidation reduction potential（Eh）under A2 and A1 oxygenation levels increased by 8.66%and 8.88%,respectively,compared with A0,and the oxygen diffusion rate（ODR）increased by 9.18%and 6.03%,respectively.The nitrogen application rate had no significant impact on Eh and ODR.During the whole growth period of tomato,A2 and A1 increased the rate of soil respiration by 43.62%and 28.02%respectively compared with A0.Oxygenation treatment significantly increased the activities of soil sucrase,urease,catalase,and phosphatase,and promoted the absorption of soil mineral nutrients by roots,increasing the accumulation of nitrogen,phosphorus,and potassium in plants.Therefore,compared to non-oxygen treatment,it reduced the content of mineral nitrogen,available phosphorus,available potassium,and organic matter in the root zone soil.（2）Oxygenation treatment promoted tomato growth.During the tomato ripening stage,the plant height at A2 aerobic level increased by 1.79%and 19.49%compared to A1 and A0,respectively.Under N3 nitrogen application level,the dry matter quality of fruit at A2 and A1 levels increased by 27.01%and 19.24%compared to A0,respectively.Oxygenation treatment also promotes the development of tomato roots and is beneficial for improving root vitality.Under the nitrogen application levels of N1 and N3,the root length of A2 and A1 increased by 19.07%to 49.41%compared to A0.Under the nitrogen application levels of N1 and N2,the root activity of A1increased by 43.03%to 46.58%compared to A0.Different nitrogen application levels have different effects on tomato growth.The height of tomato plants increases with the increase of nitrogen application rate,and the nitrogen application levels of N3 and N2increase by an average of 9.31%and 8.94%compared to N1,respectively.Under the N2 level,the fresh weight,root length,and root activity of fruits perform better.（3）At different growth stages of tomatoes,the effect of root zone oxygen supply on the photosynthetic performance of tomato leaves is inconsistent.In the seedling and fruit expansion stages,an increase in oxygen addition increases the net photosynthetic rate（Pn）.At maturity,Pn is highest at A1 level.However,during flowering and fruiting stages,oxygen addition treatment is not conducive to the improvement of Pn and performance index（PIabs）based on light absorption in tomato leaves.During the seedling stage,fruit enlargement stage,and maturity stage,the J-point of the OJIP curve significantly decreased under aerobic treatment,increasing PIabs.This indicates that root zone oxygenation promotes electron transfer on the PSII receptor side of leaves during these stages,which is beneficial for the primary photochemical reaction of PSII.The effect of nitrogen application rate on various fluorescence parameters is relatively small,and only has a significant impact on each parameter during the mature stage.Adding oxygen at the N2 nitrogen application level is most conducive to the increase of photosynthetic carbon assimilates,and the total amount of non-structural carbohydrates（NSCs）is significantly higher at the seedling stage than at other stages.The total amount of NSC treated with A2N2 during the seedling stage increased by10.97%and 22.58%compared to A1N2 and A0N2,respectively.（4）Oxygenation treatment improved the quality of tomatoes,and the soluble solid content of fruits increased by 16.42%～40.19%compared to no oxygen treatment under N1 and N2 nitrogen application levels.The organic acid content of fruits decreased by33.79%and 31.16%compared to A0 under N1 nitrogen application levels,respectively.Under the nitrogen application levels of N1 and N2,the A1 level of fruit vitamin C content increased by 14.42%to 75.10%compared to A0 and A2.Compared with A0N2,the soluble protein A1N2 and A2N2 treatments increased by 82.54%and 103.17%,respectively.The highest yield of tomato under A1N2 treatment was 44.84 t·hm^-2,but there was no significant improvement compared to A1N1.However,A1N1 treatment was more conducive to the improvement of tomato nitrogen absorption efficiency and nitrogen fertilizer productivity.Taking into account the effects of oxygen and nitrogen application on tomato yield,quality,photosynthetic physiological activities,and nitrogen absorption and utilization efficiency,it is concluded that a combination of 15mg·L^-1 oxygen application and 160 kg·hm^-2 nitrogen application throughout the entire growth period of tomato seedlings,fruit enlargement,and maturity stages is the appropriate nitrogen and oxygen addition scheme for greenhouse tomato growth in clay loam soil.