Study On Irrigation Water Lower Limits Of Drip Irrigation For Overwintering Tomato In Heliogreenhouse In Hetian Area

In order to determine the appropriate irrigation control indicators for tomatoes in solar greenhouses in Hetian area,and to provide a theoretical basis for scientific irrigation of facility agriculture in this area,from October 2020 to April of the following year,the tomato "Fen Baoli" was used as the material in Xinjiang.The Kunyu City Modern Agricultural Technology Demonstration Garden conducted an irrigation experiment and analyzed the four lower water limits of 45%,60%,70% and 80% field water retention(using T1,T2,T3 and T4)on tomato plant growth,photosynthetic changes,fluorescence parameters,yield and quality,and the gray correlation method and principal component analysis method are used for comprehensive evaluation.The main conclusions are as follows:(1)With the increase of irrigation water limit,tomato plant height,stem thickness,internode distance and leaf area index all showed an upward trend.The growth indexes of tomato under T4(80% of field capacity)treatment were significantly higher than T1(45% of field capacity)and T2(60% of field capacity)treatments(P<0.05),but there was no difference with T3(70% of field capacity)treatment.(2)A suitable irrigation water limit can help increase the chlorophyll SPAD value of tomato leaves.When the irrigation water limit is lower than 40%,the chlorophyll SPAD value of the tomato will drop sharply when the tomato is exposed to water stress.When the irrigation limit is higher than 80%,the chlorophyll content per unit area of tomato leaves will decrease.(3)When the irrigation limit is T3(70% of field capacity)treatment,tomato net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs)and intercellular CO2 concentration(Ci)are the highest,and the maximum photochemical efficiency is(Fv/Fm),the potential activity of PSII(Fv/F0),and the actual photochemical efficiency(ΦPSII)are the largest.When tomato soil irrigation is limited to 70% to 80% field holding time,tomato leaves have the largest light energy utilization rate and the strongest ability to accumulate photosynthetic products.(4)When the lower limit of soil irrigation was T3(70% field holding),the maximum yield of tomato was 113.3 t/hm2,which was41.6%、9.7% and 4.4% higher than that of T1,T2 and T4 respectively.The irrigation water use efficiency was 33.3% higher than that of T4.The water use efficiency of T1 and T3 was significantly higher than that of other treatments.Reducing the lower water limit could significantly increase the contents of TSS,SS,VC and titratable acid in tomato(P < 0.05).(5)Comprehensive evaluation and analysis of the four indicators of tomato comprehensive quality,yield,water use efficiency,and irrigation water use efficiency,the weighted grey correlation method is used for quality analysis and the principal component analysis method is used for comprehensive quality analysis,and the final result is the optimal treatment for tomato comprehensive evaluation is T3(70% field holding)irrigation water limit treatment.