Study On The Effects Of Different Upper And Lower Limits Of Irrigation On Grape Growth,Yield And Water Use Efficiency In Greenhouse

In order to determine the upper and lower limits of suitable irrigation for greenhouse grapes under automatic drip irrigation and provide theoretical basis for soil water management,experiments were carried out in solar energy-saving greenhouse with 5-year-old rose fragrance as the test material from 2020 to 2021.Based on the change of water demand in the process of grape growth,the corresponding upper and lower limits of irrigation were set in the four growth periods of germination and leaf expansion,flowering and fruit setting,fruit expansion and mature defoliation by using TDT automatic irrigation system.The indexes of grape growth,physiology,quality,yield and water consumption under different water treatments were analyzed.The results show that:（1）Effects of different upper and lower limits of irrigation on grape growth and developmentWith the decrease of the lower limit of irrigation and the amount of irrigation,the plant height,stem diameter and leaf area index of grape plant decreased.During the two-year experiment,the optimal plant height water treatment was CK,up to 185.48cm and 197.04cm respectively,the optimal stem diameter water treatment was I₁D₁and CK,up to 10.37cm and10.07cm respectively,and the optimal leaf area index water treatment was CK,up to 3.28 and3.06,which was significantly higher than that of low water treatment（P<0.05）.There was no significant difference in grape plant growth indexes between different upper limit treatments（P>0.05）.CK and I₁D₁were the most suitable treatments for grape growth and development.（2）Effects of different irrigation upper and lower limits on physiological characteristics of grapeWith the decrease of the lower limit of irrigation and the amount of irrigation,the net photosynthetic rate PN,stomatal conductance cond and transpiration rate tr all showed a downward trend.The diurnal variation showed a"bimodal type"as a whole,and the highest value appeared at 10:00.The maximum values of PN and tr are CK water treatment,and the maximum value of cond was I₁D₁.The change trend of intercellular carbon dioxide concentration CI was opposite.With the decrease of irrigation lower limit and irrigation amount,CI value increases,and CI value was the largest under I₂D₅treatment.The optimal water treatment for instantaneous water use efficiency was I₂D₂.（3）Effects of different upper and lower limits of irrigation on grape qualityAppropriate water saving is beneficial to the quality of grapes,increase the accumulation of sugar,reduce acidity and improve the color conversion.With the decrease of the lower limit of irrigation and the amount of irrigation,the content of grape soluble sugar increased and the content of titratable acid decreased.The optimal water treatment was I₁D₄,which was significantly different from other water treatments（P<0.05）.Compared with CK,the sugar content increased by 3.05%and 1.95%respectively in two years;The titratable acid content decreased by 0.53 and 0.18;The VC content increased first and then decreased.The optimal water treatment was I₂D₂and the suboptimal water treatment was I₁D₄.The color transformation of grape plants under low-level water treatment was significantly better than that under high-level water treatment.The grape plants treated with I₁D₅began to turn color 8days earlier than CK,and I₁D₄was 4 days earlier than CK.Overall,I₁D₄water treatment was the most suitable for grape quality.（4）Effects of different upper and lower limits of irrigation on water consumption characteristics of grapesReducing the lower limit of irrigation can effectively save water and significantly reduce the water consumption of grape plants.Compared with CK,other water treatments have significant water-saving effects（P<0.05）,saving 3.3～27%respectively.The water consumption intensity in each growth period shows a changing trend of gradually increasing from germination and leaf expansion stage to fruit expansion stage,and gradually weakening in mature and defoliation stage.The water consumption in fruit expansion stage accounts for54.27～62.18%of the total water consumption in the whole growth period.This growth period was the key period of water demand.The decrease of irrigation directly affects the water consumption intensity of grape plants.The change trend of daily transpiration water consumption of grape plants in each growth stage under typical water treatment is consistent with it.The transpiration water consumption in fruit expansion stage was the largest,and the liquid flow rate of high-level water treatment was higher than that of low-level water treatment.（5）Effects of different irrigation upper and lower limits on grape yield and water use efficiencyThe grain weight,ear weight and yield of grapes increased first and then decreased with the increase of irrigation.Moderate reduction of water had no significant effect on the grain weight and ear weight of grapes,and had the effect of increasing production.The yield of I₁D₁in high water treatment was the highest,increasing by 18.90%and 3.75%respectively compared with CK in two years.Severe water deficit will lead to a large reduction in yield.The yield of I₂D₅in low water treatment will be significantly reduced（P<0.05）,which was55.13%and 44.59%lower than that in CK and CK respectively.The growth and expansion process of grape seeds showed a double S-shaped change,with two expansion periods.I₂D₄was the best water use efficiency treatment,which was 46.91%higher than CK.