Study Of Tomato Growth Weight And Water Demand Model Based On Real-Time Plant Weight In A Solar Greenhouse

Solar greenhouse is a unique type of high-efficiency and energy-saving facilities in China.Due to the simple structure and imperfect supporting equipment of solar greenhouse,tomato cultivation in solar greenhouse is often in sub suitable environmental conditions in cold winter.However,the crop growth models of large-scale multi span greenhouse abroad are mostly established with appropriate environmental factors as the main parameters,which is difficult to be applied in the solar greenhouse with frequent sub appropriate environment.Therefore,starting with the phenotypic weight that directly reflects the overall change of crops,this study adopts the crop real-time weight and greenhouse real-time environment detection system to establish the simulation model of tomato plant fresh regeneration length,plant transpiration and water demand in Solar Greenhouse Based on crop real-time weight,so as to overcome the influence of greenhouse sub suitable environment and lay the foundation for automatic irrigation of Tomato in solar greenhouse.The experiment was conducted in the solar greenhouse of the facility vegetable scientific research base of Shenyang Agricultural University from March 2018 to December2019.Hobo U30 automatic weather station is used to collect environmental information.Using tomato substrate bag culture,12 sets of tomato plant real-time measurement systems were set up to record the fresh regeneration length of tomato plants in real time.After 15days of fixed value,three weighed plants were selected for destructive sampling every 7days,and the dry and fresh weight of each organ of tomato plant was weighed respectively.Compared with the classical tomgro model,the distribution of each organ of tomato plant was simulated.The actual transpiration of tomato plants was calculated by needle runoff meter,and the transpiration and water demand of tomato plants were simulated according to the change of real-time weight before and after irrigation.The main research results are as follows:1.Based on the previous research on the calculation method of fresh regeneration length of greenhouse tomato based on real-time weighing system and combined with greenhouse environmental factors,a real-time fresh regeneration length model of greenhouse tomato based on TEP was established.Seedling stage:Wg（i）=3.137DTEP（i-1）+0.737DTEP（i-2）+9.668;Flowering and fruiting stage:Wg（i）=3.613DTEP（i-1）+2.196DTEP（i-2）+5.008;Harvesttime:Wg（i）=6.781DTEP（i-1）+3.771DTEP（i-2）+18.4.On both sides of the 1:1 straight line,the determination coefficient R²is 0.817 and 0.837 respectively,the average absolute error MAE is 7.43 and 4.89,and the root mean square error RMSE is 10.09 and 6.25.The two error analysis values are relatively small.And the real-time fresh weight prediction model of tomato plant on the second day based on the real-time weighing system:through the comparison with the actual destructive sampling,the prediction of the model is better.2.According to different growth stages of greenhouse tomato,combined with radiant heat product and real-time growth,the conversion model of fresh weight and dry weight of tomato plant is established:W_dry=0.132*（W_E）-0.104*（TEP）-0.187（fixed value days≤50）,W_dry=0.132*（W_E）-0.0.743*（TEP）+88.023（50<fixedvaluedays≤80）,W_dry=0.132*(W_E-0.544*（TEP）+69.739（80<fixed value days）.W_dryis the dry weight of simulated tomato plant,g/plant;W_Eis the cumulative daily growth,g/plant;TEP is radiant heat product,MJ/m²;Furthermore,the fresh weight distribution index model of tomato aboveground organs was established based on real-time weight and radiant heat product,in which B_ST=0.361-0.001TEP,B_L=0.65+0.001TEP,B_F=0 when 0<TEP<100;B_ST=0.325-0.001TEP,B_L=1.26-0.004TEP,B_F=0.005TEP-0.511,when TEP>100,.Where:B_ST,B_Land B_Fare the distribution indexes of stems,leaves and fruits,which are verified by stubble times in different years.The absolute error（MAE）is between 0.012-0.069 and the root mean square error（RMSE）is between 0.016-0.090.Therefore,the real-time weight model of each organ is W_ST=W_E*B_ST,W_L=W_E*B_L,W_F=W_E*B_F,where W_STare the real-time weight of stems,leaves and fruits of tomato plant respectively.3.The calculation method of tomato plant transpiration in bag culture in Solar Greenhouse Based on real-time weight was established:Wd（i）=W（t,i）-W（t+u,i）.Where,Wd（i）is the weight difference of tomato before and after the i-th irrigation.The real-time weight difference between the peak value reached by the weighing system after the i-th irrigation of tomato plant and the real-time weight difference when the weighing system is stable after the i-th irrigation of tomato plant.The cumulative change of weight after all irrigation on that day is the daily transpiration of tomato plant W_T.By analyzing the effects of environmental factors on plant transpiration and overall rate,it is clear that radiant heat accumulation has the most significant effect.Therefore,a model of tomato plant transpiration in bag culture in Solar Greenhouse Based on real-time weight and radiant heat accumulation is established:W_TN=W_T+80.42+2.61DTEP²（flowering stage）;W_TN=W_T+196.51-6.12DTEP²（result period）;W_TN=W_T+55.34DTEP（harvest time）,W_TNis the daily transpiration of your tomato plant.It was verified in the winter and spring stubble and autumn and winter stubble of 2019 respectively,and the correlation coefficient R²between the simulated value and the actual value was more than 0.8.Using the transpiration simulated by the weighing system combined with radiant heat product can accurately simulate the daily transpiration of tomato plants.4.Two kinds of water demand prediction models of bag cultured tomato plants in Solar Greenhouse Based on real-time weight were established.The prediction model of tomato plant water demand based on real-time dry matter accumulation and real-time transpiration in solar greenhouse:W_W（i）=0.761*W_TN（i-1）+2.096*W_dry（i-1）+230.89,W_W（i）is the simulated water demand of tomato plant based on transpiration and dry matter mass on day i,g/d;W_dry（i-1）is the amount of dry matter of tomato plant on day（i-1）,g/d.Through the verification of tomato planting in different stubbles,the change trend of water demand is basically consistent.Most points are distributed on or close to the straight line of y=x,and only a few values deviate from the straight line.R²is 0.88 and 0.75 respectively.The water demand of tomato planting can be predicted according to the transpiration and dry matter quality of tomato plants on that day;The water demand models of different stubbles based on the amount of plant dry matter and radiant heat accumulation were established through the regression equation.For winter and spring stubbles:Z₁=158.38x+94.18y+337.03;Autumn and winter stubble:Z₂=126.91y-47.27x+601.41,x is radiation thermal product（TEP）;y is the daily dry matter growth of tomato plant;R²was above 0.7,and the performance of autumn and winter stubble was higher than that of winter and spring stubble.Compared with the two models,based on the water demand model of tomato plant transpiration and dry matter mass,from the research on the change of tomato plant’s own weight,the simulation is carried out according to the change of tomato plant’s weight after irrigation and the accumulated dry matter mass of tomato plant,which is less affected by the environment.The model synthesized by the quality of two important parameters can predict the water demand of tomato plant in the next day,whether in winter,spring or autumn and winter,It can be used as an effective method to estimate the water demand of tomato plants,and provide theoretical and technical support for the precise irrigation control of tomato plants in solar greenhouse.