Study On Nutrient Solution Drip Irrigation Strategy Of Tomato In Bag Culture Based On Leaf And Temperature

Tomato is one of the main vegetable crops in facility cultivation.With the rapid development of facility agriculture in China,the substrate cultivation area of tomato is also increasing.Adjusting the drip irrigation and fertilization system is an important agricultural management method to improve vegetable quality and yield.In substrate cultivation,drip irrigation nutrient solution is the main method of fertilizer supply,but there is currently a lack of scientific nutrient solution management strategies for short stubble tomato in bag culture.Therefore,in 2020 and 2021,this study designed two experiments with ’Hesheng Feilong’ tomato as the experimental material,and each experiment was repeated twice.The drip irrigation strategy of tomato was determined from four aspects: drip irrigation frequency,drip irrifgation time,drip irrigation volume,and nutrient solution supply method.The experimental treatments are:(1)Taking the conventional nutrient solution management method that adjusts the nutrient solution supply according to the growth period as a control,and designed to dynamically adjust the nutrient solution supply according to the leaf growth,for each additional true leaf,the nutrient solution was increased by 80 m L/plant,90 m L/plant,100 m L/plant,after topping,the nutrient solution supply was constant.4 treatments in total.(2)Set three drip irrigation frequencies(1 time/d,3 times/d,5 times/d)and two start drip irrigation times(8:00 and 9:00),there was 6treatments.By analyzing the effects of different treatments on tomato dry matter and distribution,photosynthesis,element absorption and utilization,substrate enzyme activity,yield and quality,the comprehensive evaluation method was used to evaluate each treatment,and then determined the optimal nutrient solution supply mode and drip irrigation frequency and time.By analyzing the relationship between the change of substrate moisture content and the temperature of the optimal drip irrigation frequency and time treatment,the influence of temperature on the change of substrate moisture was explored.The water demand of tomatoes could be indirectly calculated,and then we determined the drip irrigation volume.The main research results are as follows:(1)Compared with the conventional nutrient solution management method,the management method based on the dynamic supply of nutrient solution depended on leaf growth can increase the dry matter weight of tomato and promote the distribution of dry matter into the fruit,improve tomato photosynthesis and substrate enzyme activity,increase yield and improve fruit quality,but had no positive effect on element absorption and utilization.Through the comprehensive evaluation of yield and quality,T2 treatment was the optimal treatment,which saved 7380 and 4841 m L of nutrient solution per tomato plant in 2020 and 2021,respectively,compared with conventional management.Therefore,it is recommended to use a dynamic nutrient solution management strategy of increasing the amount of nutrient solution by 90 m L for each additional tomato leaf.(2)Increasing the frequency of drip irrigation within a certain range can improve the dry matter quality of tomato;the activities of substrate urease and catalase were mainly affected by the drip irrigation frequency,and the drip irrigation time had no significant effect on them;the frequency and time of drip irrigation under different cultivation seasons and environments had different effects on the yield.Four single comprehensive evaluation methods of PCA,TOPSIS,MFA and GRA were used to comprehensively evaluate fruit quality,and fuzzy Borda combination evaluation was carried out on the evaluation results of the single comprehensive evaluation methods that passed the consistency test(Kendall-W),and MFA was determined as the most suitable single evaluation method for evaluating tomato quality cause its results had the highest correlation coefficient with the results of fuzzy Borda combined evaluation,which were 0.989 and0.994 in 2020 and 2021,respectively.In addition,the total soluble solid content was significantly positively correlated with the score value of MFA,therefore,the total soluble solid content can be used as a single quality indicator representing the comprehensive quality of tomato.Through TOPSIS analysis of the total soluble solid and yield,it was determined that the optimal drip irrigation frequency was 5 times/d,and the drip irrigation time was 9:00,11:00,13:00,15:00 and 17:00.The K-means clustering algorithm was used to analyze the optimal treatment and to determine the changes in the moisture content of the substrate corresponding to different temperature ranges.We calculated the drip irrigation volume by converting.According to the temperature range,the drip irrigation volume can be determined as: during the daytime(9:00-19:00)time period,it was divided into three ranges,the temperature ranges were 5.90℃-23.98℃,23.98℃-37.42℃,37.42℃-53.58℃,corresponding to 0.44%/2h(40 m L/2h),1.34%/2h(121 m L/2h),2.26%/2h(203 m L/2h)respectively;at night(19:00-9:00 the next day),the change in moisture content of the substrate was 0.19%/2h(17 m L/2h).To sum up,the final drip irrigation strategy for bag-cultured tomato was as follows:dynamically adjust the nutrient solution supply according to the leaf growth,the amount of nutrient solution increased by 90 m L for each additional leaf;in the tomato fruiting period,the drip irrigation frequency was 5 times/d,the drip irrigation should be carried out at 9:00,11:00,13:00,15:00 and 17:00,and the drip irrigation volume is determined by temperature range: During the day(9:00–19:00),the change in substrate moisture content is divided into three temperature ranges,namely,5.90°C–23.98 °C,23.98°C–37.42°C,and37.42°C–53.58°C,which correspond to 0.44%/2 h(40 m L/2h),1.34%/2h(121 m L/2h),and2.26%/2h(203 m L/2h),respectively.During the night(19:00–9:00 the next day),the change in substrate moisture content is 0.19%/2h(17 m L/2h).