Study On Water-Nitrogen Interaction Effects And The Optimalization Management Of Irrigation And Nitrogen In Greenhouse Tomato

Solar greenhouse planting,a common way for fruits and vegetables production,which has long been faced serious problems of low water-nitrogen use efficiency,soil quality degradation and low fruit quality.In order to achieve the goal for fruits and vegetables production with high level of quality,yield,efficiency and characteristics of green environmental protection.This paper took greenhouse tomato as the research object,and irrigation amount was determined based on the cumulative evaporation(E_pan)measured with a standard 20-cm pan.There were three levels of irrigation amount(irrigation quotas were 50%,70%and 90%of E_pan,denoted as I1,I2 and I3,respectively)and four levels of nitrogen rate(0,150,300 and450 kg N·ha^-1,denoted as N0,N1,N2 and N3,respectively).The water-nitrogen interaction effect on plant growth,soil environment,water consumption,yield,quality and water-nitrogen use efficiency of greenhouse tomato were investigated by the 3-year fixed position experiment.The regulation mechanism of water-nitrogen interaction on yield and fruit quality of greenhouse tomato were revealed.Tomato quality was comprehensively evaluated by the technique for order preference by similarity to an ideal solution(TOPSIS),grey relation analysis(GRA),principal component analysis(PCA)and combination evaluation method(CEM),and the simplified index of tomato comprehensive quality was developed.The optimal irrigation and nitrogen application mode was proposed to balance the yield,biomass,quality and water-nitrogen use efficiency of tomato.The main results were as follows:(1)The effects of water-nitrogen interaction on plant growth and development of greenhouse tomato were revealed.The morphological indexes of tomato growth and development increased with increasing irrigation amount.Under the condition of I1 level,appropriate increase in nitrogen rate was favorable for improving plant height,leaf area index(LAI)and biomass accumulation,but when the nitrogen rate exceeded the N2 level,the plant height,LAI and biomass accumulation no longer increased,and even showed a certain downward trend.For the I2 level,the plant height and biomass accumulation significantly increased with the increase in nitrogen rate,while LAI increased first and then decreased.At the I3 level,the plant height,LAI and biomass accumulation increased with the increase in nitrogen rate.Decrease in irrigation amount reduced the net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)of tomato leaves,but increased the instantaneous water use efficiency of leaves(WUE_Y).Increase in nitrogen rate improved Pn,WUE_Y and chlorophyll relative content(SPAD).Pn,Tr,WUE_Y,Gs,photosynthetic active radiation(PAR)and canopy temperature(Tc)increased with the increase in spike layer.The fruit size(transverse diameter,longitudinal diameter,fruit diameter and volume)had the extremely significant Logistic function curves with days after flowering,effective accumulated temperature after flowering and total photosynthetically active radiation after flowering.(2)The response of soil environmental factors to water and nitrogen supply in greenhouse was revealed,and the community composition of soil bacteria and fungi and their relationship with soil environmental factors were proved.Increase in irrigation amount significantly reduced the soil urease activity,but had insignificant effect on soil sucrase and alkaline phosphatase activities and the soil microorganism.The activities of soil urease and alkaline phosphatase significantly increased at first and then decreased with the increase of nitrogen rate,and reached the maximum at N1 level,the activities of soil sucrase significantly increased with the increase of nitrogen rate,however,compared with N2,the activities of soil urease and alkaline phosphatase in N1 decreased by 3.44%and 11.76%,respectively,while the activity of soil sucrase only increased by 10.83%The relative abundance index of bacterial OTU significantly increased with the increase of nitrogen rate,but there was no significant difference among N1,N2 and N3.The relative abundance index of fungi OTU significantly decreased with the increase of nitrogen rate,but there was no significant difference between N0 and N1.Increasing nitrogen rate significantly increased the relative abundance of soil bacterial dominant species Actinobacteriota,compared with N0 level,the relative abundances of Actinobacteria in N1,N2 and N3 increased by 7.28%,9.34%and 10.74%,respectively.Nitrogen application only had a significant effect on the relative abundances of soil fungal dominant species unclassified?f?Microascaceae,which was the highest at N2.The effects of irrigation and nitrogen rate on the dominant bacterial community in soil were mainly realized by changing the contents of soil ammonium nitrogen,electrical conductivity,alkaline hydrolysis nitrogen,organic matter,p H and nitrate nitrogen,and the effects of irrigation and nitrogen rate on the dominant fungal community in soil were mainly realized by changing the contents of soil available potassium,available phosphorus,organic matter,total nitrogen,p H and electrical conductivity(3)The effects of water and nitrogen supply on each spike fruit yield composition and water-nitrogen use efficiency of greenhouse tomato were investigated.Increasing irrigation amount significantly increased each spike fruit-setting number of tomato fruit,whereas when irrigation amount increased to a certain extent(I3),fruit-setting number did not increase significantly.Appropriate nitrogen rate(no more than N1)was beneficial to tomato fruit-setting,while excessive nitrogen application did not significantly increase the fruit-setting,even had a downward trend(except the 4^th-spike).Increasing irrigation amount could significantly increase the average fruit weight each spike fruit,and increasing nitrogen had insignificant effect on the average fruit weight averaging across all spike fruits.Nitrogen rate mainly impacted the tomato yield by affecting the fruit-setting number,and irrigation mainly affected the yield by influencing the average single fruit weight.Increasing irrigation amount could significantly increase yield,nitrogen partial factor productivity(PFP_n)and nitrogen absorption use efficiency(NAE),but reduce water use efficiency(WUE),and had insignificant effect on nitrogen physiological use efficiency(NUE).Yield and WUE increased first and then decreased with the increase of nitrogen rate,and both reached the maximum at N2 level,but only increased by 1.36%and 2.01%compared with N1 level,respectively.While PFP_n,NUE and NAE decreased significantly with the increase of nitrogen rate.(4)The effect mechanism of water-nitrogen interaction on tomato quality formation was explored,and the evaluation method suitable for the comprehensive fruit quality of greenhouse tomato was proposed,the simplified index-total soluble solids(TSS)could be used to characterize fruit comprehensive quality was determined.The change of vitamin C(Vc)in fruit between spike layers was caused by light,the change of soluble sugar content(SSC)was induced by total solar radiation,fruit water content and nutrients,the change of organic acid(OA)was regulated by the total nitrogen content of fruit and temperature,the change of sugar acid ratio(SAR)was controlled by SSC and OA,and the impact factors for TSS were same with that for SSC.With the increase of irrigation amount,the contents of TSS,Vc,SSC and OA in each spike fruit significantly decreased due to the decrease of fruit nutrient absorption and the dilution of fruit water content,and the dilution of fruit water content was the main influencing factor.Appropriately increasing nitrogen rate could improve fruit quality each spike,which was caused by the increase of fruit nutrient absorption,the increase of photoassimilate and the concentrated fruit water content,and the increased of the photoassimilate and fruit nutrient absorption was the main influencing factor.The results showed that the PCA and GRA were suitable for the evaluation of comprehensive fruit quality,and the evaluation results were agreed on the N3I1 treatment(nitrogen rate of 450 kg N·ha^-1+irrigation amount of 50%E_pan)with the best comprehensive fruit quality.Moreover,the comprehensive fruit quality score was significantly positively correlated with TSS,so TSS can be used as a simplified index to evaluate tomato quality.(5)The optimal management of irrigation and nitrogen for greenhouse tomato was developed.Taking tomato yield,biomass,WUE,PFP_n and TSS as the original evaluation index system,the TOPSIS and GRA methods were used to analyze and evaluate the comprehensive benefits of irrigation and nitrogen application mode of greenhouse tomato.The results showed that N1I2(150 kg N·ha^-1+70%E_pan)had the best comprehensive benefit,and N3I1(450 kg N·ha^-1+50%E_pan)was the minimum.Combined with the optimal soil environments,the comprehensive analysis confirmed that N1I2 was a water-saving,high-quality,efficient and environmentally friendly irrigation and nitrogen management for greenhouse tomato.