Effects Of Water-fertilizer-gas Coupling On Water Consumption And Quality Of Drip Irrigation Processing Tomato

Object:Xinjiang is the largest processing tomato production base in China.The unique advantages of planting and processing tomatoes combined with the drip irrigation planting mode under mulch make Xinjiang’s processing tomatoes extremely competitive in the international market,but meanwhile,mulching hinders soil CO₂ emissions,destroys the dynamic equilibrium system of O₂ production and diffusion has changed the water and heat conditions of the soil,and exacerbates the hypoxia of crop root zone.Tomato is one of the most sensitive crops to insufficient oxygen supply in the soil.Hypoxia in the root zone will affect root growth,reducing the absorption of water and nutrients and the transmission of nutrients to the plant body,thereby limiting plant growth and yield.Water-fertilizer-gas coupling drip irrigation,based on the water-fertilizer drip irrigation system,uses aerated equipment to transport water-fertilizer-gas mixture to the soil of the crop root zone,which not only meets the crop’s demand for water and fertilizer,but also satisfies the aerobic respiration of crop roots and soil microorganisms demand for oxygen,thus promoting the growth of crops,increasing yields and improves crop quality.This experiment passed a two-year field experiment to study the effects of different water and fertilizer treatments on soil moisture,soil respiration,nitrogen absorption and distribution,fruit yield and quality index of processing tomato,these results could provide theoretical support for improving water-fertilizer use efficiency of processing tomato in Xinjiang.Methods:The experiment set W1（4 950 m³/hm²）and W2（4 050 m³/hm²）two irrigation levels,N1（280kg/hm²）,N2（250 kg/hm²）,N3（220 kg/hm²）and N4（190 kg/hm²）4 nitrogen levels,A（aerated irrigation,aerated ratio of 15%）and C（non-aerated irrigation,aerated ratio of 0%）2 aerated levels.There were a total of 16 treatments,with 3 repetitions for each treatment.The test treatment of aerated irrigation used a Mazzei air injector（Mazzei 1078）for aeration.Results:（1）There was a positive correlation between soil moisture content and irrigation amount.Under too high and too low nitrogen application rate,the soil moisture content was higher,and the average soil moisture content of 0-20 cm and 0-40 cm soil layer were reduced by 2.71%and 0.41%,and 40-70 cm increased by 0.44%.The water consumption of processing tomato increased with the increase of irrigation amount and nitrogen application rate.Compared with the non-aerated treatment,the water consumption of processing tomato was increased by 3.07%during the growth period of tomato.The water consumption,water consumption modulus and water consumption intensity of each treatment all reached the maximum value at the fruit expansion stage.（2）Irrigation,nitrogen,and aeration significant effected on soil respiration in each growth period of processing tomato,and the soil respiration of each treatment reached its maximum during the fruit swelling stage of processing tomato.The soil respiration of processing tomato was greater as the irrigation level decreased,and it first increased and then decreased as the increase of nitrogen level.Aeration treatment increased the soil respiration rate of processing tomato,and the aerated soil respiration increased more obviously under high irrigation amount.（3）Under high irrigation rate,the content of inorganic nitrogen in 0-60 cm soil decreased,and increased the content of inorganic nitrogen with the increase of nitrogen levels in 0-60 cm soil.Under aerated irrigation,the content of ammonium nitrogen and nitrate nitrogen in 0-60 cm soil increased by 1.99%and 7.12%,respectively.Aerated irrigation increased the content of inorganic nitrogen in 20-40 cm soil layer the most.The nitrogen accumulation in all organs of processing tomato under different treatments was the largest in fruit.The increase of irrigation amount increased the total nitrogen content in all organs,and the total nitrogen accumulation of processing tomato under aerated treatment increased by 14.80%.（4）Increasing irrigation volume increased plant height,Pn（net photosynthetic rate）,Tr（transpiration rate）,Gs（stomatal conductance）and dry matter quality of processed tomatoes,but reduced the crop stem thickness and Ci（intercellular CO₂ concentration）;The stem thickness,Pn,Tr,Gs,Ci and dry matter quality of processing tomatoes increased firstly and then decreased relative to nitrogen levels.Compared with no aerated irrigation,the plant height,stem thickness,Pn,Tr,Gs and dry matter mass were significantly increased by 4.98%、3.70%、6.84%、11.41%、12.33%and 10.74%under aerated irrigation（P<0.05）,but Ci reduced 4.63%.（5）Increasing irrigation water increased the yield of processing tomato and partial productivity of nitrogen fertilizer,but reduced the efficiency of irrigation water use.The yield and the coefficient of irrigation water utilization firstly increased and then decreased relative to nitrogen levels,and nitrogen partial factor productivity gradually decreased;Compared with the aerated treatment,the yield under the aerated irrigation increased significantly by 2.32%-10.02%（P<0.05）,and irrigation water-use efficiency and nitrogen partial productivity were significantly increased by 6.12%and 6.19%（P<0.05）,respectively.The soluble sugar,lycopene,vitamin C and soluble solids of processed tomatoes increased firstly and then decreased with the increase of nitrogen levels,and decreased with the increase of irrigation level;aerated irrigation increases soluble sugar and organic acid compared with no aerated irrigation,Vitamin C,lycopene,soluble solid content,but reduced the sugar-acid ratio of the fruit.Conclusion:In this experiment,considering the law of water consumption,dry matter accumulation,physiological growth characteristics,yield,quality,water and fertilizer utilization efficiency of processing tomato,combined with principal component analysis and comprehensive membership function evaluation results,the comprehensive rankings revealed the suitable irrigation amount was 4 050 m³·hm^-2 and the suitable nitrogen amount was 250 kg·hm^-2 under aerated irrigation conditions.