Effect Of Water Nitrogen Coupling On Tomato Growth In Greenhouse Under Drip Irrigation

Tomato is one of the economic crops widely planted in China,which has a large market demand.Over the years,farmers have been blindly irrigating and applying nitrogen for increasing production and improving efficiency,resulting in waste of water resources,excessive application of nitrogen,low utilization of water and nitrogen,poor quality of tomato fruit and other adverse effects.Water and nitrogen are the important factors that determine the high-efficient and high-quality production of tomato.Through the reasonable coupling of water and nitrogen,the yield of tomato can be increased,the quality of tomato fruit can be improved,and the utilization efficiency of water and nitrogen can be improved to a certain extent.To maximize the coupling effect of water and nitrogen is an urgent problem for the sustainable development of tomato planting industry.The experiment was conducted from May to September 2019 in the greenhouse and the plastic greenhouse of the Dry Land Agricultural Research Center of Shanxi Academy of Agricultural Sciences,which is located in Yangqu,Shanxi Province.In the experiment,nitrogen and irrigation in different growth periods were used as variables,the irrigation and nitrogen application of tomato were designed by four factors and three levels orthogonal test to study the coupling effect of water and nitrogen and irrigation in different growth period on the growth,yield and quality of tomato,the growth change of tomato plant height and stem was diameter by establishing the logistic growth model of tomato plant growth,tomato yield was simulated by establishing water and nitrogen production function,The"water-quality"model of tomato was used to simulate the quality index of tomato,the Principal Component Analysis was used to comprehensively merit quality indexes of tomato.The results are as follows:（1）The soil moisture content decreased first,then kept flat,and finally gradually increased with the development of growth period before irrigation in different periods;the change of soil average moisture content in each growth period is basically consistent with the change of irrigation.With the same amount of irrigation,the average water content of soil increases first and then decreases with the amount of nitrogen application.The accumulation content of soil nitrate increased with the increase of nitrogen application,and mainly concentrated on the surface of soil;with the increase of irrigation amount,nitrate nitrogen in soil moved to the depth of soil layer;the content of nitrate nitrogen decreased first and then increased with the development of growth period.（2）The plant height and stem diameter of tomato increased gradually with time and then became stable,and the growth of plant height and stem diameter was improved with the increase of nitrogen application and irrigation.Tomato plant height in the late seedling stage,the fastest growth rate;and the main growth stage of tomato stem diameter was within 10～40 days after planting.The effect of irrigation at flowering and fruit setting stage on tomato plant height reached a significant level,and the effect of nitrogen application and irrigation at Seedling Stage on tomato stem diameter reached significant level.The logistic growth model has high accuracy in the simulation of plant height and stem diameter."A1B1C2D1"was the ideal treatment for the growth of tomato plant height and stem diameter.The irrigation amount in seedling stage,flowering and fruit stage and mature stage was I,I,0.75I and nitrogen application amount was 350 kg·hm^-2.（3）The tomato yield of each treatment was"T1>T4>T7>T2>T5>T6>T9>T8>T3".Tomato yield was increased with the increase of nitrogen application,and with the irrigation amount in flowering and fruit setting stage and maturity stage,the yield was increased.With the increase of irrigation amount at seedling stage,the yield of tomato was first increased and then decreased.The effect of irrigation amount on yield was significant（P<0.05）.The ideal water nitrogen coupling mode with the highest yield is"A2B1C1D1".The irrigation amount in seedling stage,flowering and fruit stage and mature stage was 0.75I,I,I and nitrogen application amount was 350 kg·hm^-2.The water consumption of tomato crops in each treatment was 180.82～286.773 mm,and was increase with the increase of irrigation water.The correlation between WUE and irrigation was negative,the correlation between PFPN and nitrogenous fertilizer amount was negative.Considering yield,WUE and PFPN,T2 treatment(I,0.75I,0.75I,250kg·hm^-2)had the best comprehensive benefit.（4）Based on Jensen model of"water-yield",the function model of water and nitrogen production of tomato was constructed by introducing nitrogen factor.Determination coefficient R² was reached at 0.875,and it has a good simulation effect,calculate the performance of water sensitive indexλwas"Flowering and fruiting stage>mature stage>seedling stage".The model was verified by the measured data of the water nitrogen coupling test in the greenhouse,The RMSE of calculated value and measured value was 2.34 t·hm^-2,the MRE was 2.71%,and the MAD was 1.38 t·hm^-2,the results show that the model has high simulation accuracy and can be used to predict the yield of water nitrogen coupling tomato.（5）The effect of irrigation amount on organic acid,VC,nitrate,soluble solids and sugar acid ratio of tomato in mature stage was significant（P<0.05）.The content of soluble sugar,VC,nitrate and soluble solid decreased with the increase of irrigation amount at maturity;Organic acids was first increased and then decreased with the increase of irrigation amount at maturity;The ratio of sugar to acid was decreased first and then increased with the increase of irrigation amount at maturity;Soluble sugar and organic acid was decreased first and then increased with the increase of nitrogen application;VC content,nitrate content and sugar acid ratio was decreased first and then increased with the increase of nitrogen application.（6）Three"water-quality"models were used to simulate the tomato quality.The three models all have good simulation results in the fitting of tomato soluble sugar,organic acid and VC.The correlation coefficient R is0.7063～0.9084.In the process of model validation,the correlation coefficient of nitrate and sugar acid ratiois generally low.It is recommended to use additive model to simulate the relationship between soluble sugar,organic acid,soluble solid and water,and use exponential model to simulate the relationship between water and VC.The quality indexes of tomato,yield,WUE and PFPN were analyzed by principal component analysis,T7 was the best coupling treatment of water and nitrogen for tomato,which irrigation in seedling stage,flowering and fruiting stage and maturation stage were 0.5I,I and 0.5I,and the nitrogen was 250kg·hm^-2.