Study On Thermal Stability Of Leaf Vegetable Production System

Day and night temperature difference is big in solar greenhouse,the unstable environment has a bad effect on leaf vegetables production,Therefore,a hydroponic production system for leaf vegetables was developed.the system is 6 m long,5.4 m wide and total height 1 m,The arch part is high 60cm and the liquid culture pond is high 40cm,the performance and related factors were studied,and the results were as follows1.Nutrient solution is more suitable for crops to grow in the winter observation day.The average temperature of the nutrient solution is 2.6 centigrade higher than that in the soil,and the daily range is 6.3 degrees lower than that of the soil.The temperature of nutrient solution varies 1 degrees,and the heat is 20412KJ,while the soil needs 3606KJ.The heat capacity of nutrient solution is 5.7 times that of the soil.It indicates that nutrient solution a better thermal stability.Nutrient solution can be adjusted to the air temperature in the production system,and the average amount of heat absorbed by the air in the production system of the nutrient medium is more 162KJ than soil per day.2.The coverage rate of the planting plate will affect the environmental conditions in the production system.The greater the coverage rate of the planting plate,the more stable the temperature of the nutrient solution.When the coverage rate of planting plate is 100%,75%and 50%,the daily diurnal range of nutrient solution temperature is 4.8,5.5,7.7.Reduce engraftment plate coverage can make nutrient solution absorbs more heat,but also lose more heat in the night.When engraftment plate coverage rate of 50%,nutrient solution heat change most,engraftment plate coverage rate was 75%,26%fewer calories than 50%coverage of nutrient;the nutrient liquid heat ratio 50%coverage rate is reduced by 39%.3.The position of the system is 12cm under the position of the nutrient liquid pool in the production system,and the environment is more stable.The control(ground position),high(above ground 10cm)and low(lower concave 12cm)nutrient solution in the production system can store heat were 13444KJ,17391KJ,11893KJ,compared with the control group,29%of the heat storage high nutrient solution in the production system,low production system less heat storage 12%.When the bottom of the nutrient pool of the production system is below the ground,the surrounding soil surrounding the nutrient pool will play a moderating role in the system's environment.When the bottom of the nutrient pool is higher than the ground,the soil at the bottom of the nutrient solution will increase the heat in the system.4.The greater the volume of the nutrient solution in the production system,the more stable the environment in the system.The daily temperature of nutrient solution in the production system with nutrient solution depth of 25cm,20cm and 15cm is 2.3,2.8,4.3,and the temperature of nutrient solution varies by 1 degrees.The required heat is 33600KJ,27300KJ and 21000KJ respectively.The air in the production system is regulated by the nutrient solution,and it also shows that the temperature change is more stable with the increase of the amount of nutrient solution.5.The increase of polystyrene board around the production system can reduce the loss of the heat of the nutrient solution in the system,and paving polyphenyl plates at the bottom are better than the surrounding pavingTo sum up,the use of the leaf vegetables production system,can adjust seasonal combined with the position of production system,dosage of nutrient solution,Engraftment plate cover,means and so on,to regulate indoor environment,to facilitate the production of leaf vegetables.