Effects Of CO₂,Root-zone Temperature And Nutrient Solution Interaction On Tomato Growth And Nutrient Uptake

With the development of agricultural intelligence,the technology of controlling greenhouse environment is more and more mature.By controlling the temperature,humidity,CO2 concentration and other environmental factors of greenhouse,people create a more suitable environment for crop growth.Especially in soilless cultivation,the substrate has a strong dependence on the greenhouse environment,and the change of environment caused the change of crop growth and water and nutrient uptake by plants were more significant.So in this study,two experiments were set up through the cultivation of rock wool,which tomatoes were taken as research object.The first experiment was in an artificial climate chamber,where was set two levels of CO2 concentration,respectively C1(400~600 μmol·mol-1)and C2(800~1000μmol·mol-1),and three EC levels,respectively E1(2.3 m S·cm-1),E2(2.9 m S·cm-1),E3(3.5 m S·cm-1).The second experiment was in intelligent greenhouse,where was set two root zone temperature,respectively T1(no heating in the root zone at seedling period)and T2(the root zone was heated to 20 ℃ for 29 d at seedling period),and three EC levels in seedling period,flowering period and fruiting period,respectively TE1(1.5-1.9-2.3 m S·cm-1),TE2(1.9-2.4-2.9 m S·cm-1),TE3(2.3-2.9-3.5 m S·cm-1).By measuring the growth,photosynthesis,quality,yield,nutrient absorption,and water and nutrient use efficiency of tomatoes under different treatments,analyzing the effects CO2 concentration,root zone temperature and nutrient solution EC on them,which provided theoretical basis for environment and irrigation coupling regulation of rock wool cultivation of tomato in intelligent greenhouse.The main conclusions of this study are as follows:(1)The growth and yield indexes under the interaction of CO2 and EC show: The plant height,stem diameter and leaf number were increased with the increase of CO2 concentration,while the nutrient solution EC had no significant effect on plant height and leaf number,but the stem diameter was increased with the increase of EC.The Yeild of per plant significantly increased with CO2 concentration.Compared with C1,the C2 had increased by 23.8%-40.5%.And the yield of per plant of E2 had the highest yield at the two CO2 concentration levels.Compared with E1 and E3,the E2 had increased by 13.5%-14.6% and11.0%-26.0%,respectively.(2)The quality indexes under the interaction of CO2 and EC shows: At the same EC level,the soluble solid,titrable acid,soluble sugar of C2 had decreased by 5.3%-16.4%,16.7%-42.9%,0-22.7%,respectively,and the vitamin C of C2 had increased by 2.5%-14.49%,compared with the treatment C1;At the different CO2 concentration levels,the EC had different effects on quality indexes of tomato.At the C1 level,the soluble solid,titrable acid,soluble sugar were highest under E2,the vitamin C was highest under E3.Compared with E1,these quality indexes of E3 had increased by 27.0%,16.7%,22.2% and 31.6%,respectively.At the C2 level,all quality indexes were highest under E3,which had increased by 8.0%,25%,40% and 47.8%,respectively,compared with E1.(3)The water and nutrient use efficiency indexes under the interaction of CO2 and EC shows: At the same EC level,improved CO2 concentration was beneficial to water and nutrient use efficiency.Compared with low CO2 concentration,the water and nutrient use efficiency of high CO2 concentration were increased by 11.0%~33.2% and 10.9%~85.1%,respectively;At the same CO2 concentration level,the water and nutrient use efficiency were first increased and then decreased with the EC increase,which were highest under E2.The results indicated that the highest water and nutrient use efficiency were under the treatment C2E2,which were 43.74 g·L-1and 19.61 kg·kg-1,respectively.(4)The growth and photosynthetic indexes under the interaction of root zone temperature and EC shows: At the same EC level,the net photosynthetic rate,transpiration rate,and intercellular CO2 concentration were increased with the heating of root zone.And the root zone heating promoted the plant height of tomato in seedling period and stem diameter of tomato in entire growth period growth.At the same root zone temperature level,as the plants grows,increasing the nutrient solution EC was good at plant height growth.(5)The single fruit weight and yield indexes under the interaction of root zone temperature and EC shows: At the same EC level,root zone heating significantly increased tomato single fruit weight and yield.Compared with T1,the single fruit weight and yield of T2 had increased by 13.2%~23.3% and6.4%~11.6%,respectively.At the same root zone temperature level,increasing nutrient solution EC significantly reduced tomato single fruit weight and yield.Compared with E1,the single fruit weight and yield of TE3 had decreased by 12.2%~19.4% and 21.3%~24.1%,respectively.(6)The water and nutrient use efficiency indexes the interaction of root zone temperature and EC shows: At the same EC level,root zone heating significantly increased water and nutrient efficiency.Compared with root zone no heating,the water and nutrient use efficiency of root zone heating had increased by 9.3%~25.8% and 8.4%~17.3%,respectively.At the same root zone temperature level,increasing nutrient solution EC significantly reduced the water and nutrient use efficiency.The results indicated that the highest water and nutrient use efficiency were under the treatment T2TE1,which were48.76 g·L-1and 32.72 kg·kg-1,respectively.