椰糠条栽培番茄的蒸腾反馈智能灌溉系统研制

Development of transpiration feedback intelligent irrigation system for tomato under coconut coir slabs cultivation condition

为满足番茄椰糠条栽培条件下自动精量灌溉的需要,该研究研制了一套蒸腾反馈智能灌溉系统,包括蒸腾检测组件、通信组件、决策组件和灌溉组件。蒸腾检测组件基于压力传感器测定番茄蒸腾量;决策组件基于椰糠条的持水特性和番茄蒸腾量的变化建立了灌溉精量控制模型,精确控制水泵启动和关闭,使灌溉量根据作物蒸腾量的多少变化,并根据回液量及其电导率(Electrical Conductivity,EC)值变化判断调用正常灌溉模式或淋洗模式,使椰糠条始终处于适宜的含水量范围内,保持一定的水气比,以利于番茄根系生长和吸收营养液,解决灌溉不足造成的干旱胁迫和灌溉太多造成的营养液浪费和回液处理量大的问题;通信组件用于各模块间信号的传递。以荷兰RIDDER公司研发的基于光辐射积累量控制的灌溉系统为对照,检验该蒸腾反馈智能灌溉系统的应用效果。结果表明,在番茄盛果期,该系统的灌溉量比对照增加9.4%,回液量减少18%,且回液EC值比较稳定;与定时灌溉相比,减少灌溉量32%,减少回液量57%,有更多的营养液被植物吸收利用。栽培效果显示,使用该系统灌溉的番茄产量、株高、节数与使用荷兰RIDDER公司研制的灌溉系统的没有显著差异,取得了与之相同的灌溉效果;而且,在5 000 m^(2)温室内设备设计使用年限10 a条件下,该智能灌溉系统年运行成本与之相比还降低了20.8%,并能够满足自动精量灌溉的需求。若根据基质类型不同调整灌溉控制模型参数,该系统也可应用于岩棉条栽培、混合基质盆栽等其他无土栽培的智能精量灌溉。

To meet the requirements of automatic precision irrigation for tomato cultivation on the coco coir slabs,a transpiration feedback intelligent irrigation system was developed in this study.The system included the substrate water content detection component,the communication component,the decision component,and the irrigation component.The transpiration detection component detected tomato transpiration based on the load cell,the decision component established the precision irrigation control model based on the water holding capacity of coco coir and tomato transpiration,which accurately controlled the pump start-up and turn off,so that the irrigation amount changed with the transpiration rate.The precision irrigation control model had two modes which were normal irrigation mode and flushing mode.When transpiration amount and Electrical Conductivity(EC)value were high,the flushing mode was called,otherwise,the normal irrigation mode was called.The day was divided into four periods.The first period was from sunrise to midday,when the transpiration rate gradually increased,the water content of the substrate should be gradually irrigated to the water holding capacity;the second period was from midday to the end of flushing,when the instantaneous water content of the substrate should be maintained above the water holding capacity to flush the excess salt in the substrate;the third period was from the end of flushing to a moment before sunset,at which time the water content of the substrate should be maintained around the water holding capacity to meet the needs of high transpiration rate in the afternoon,to ensure that there was sufficient water and nutrients to meet the needs of tomato photosynthesis;the fourth period was from the moment before sunset to the second day before the start of irrigation,at which time the water content of the substrate should gradually fall back to the lower limit of the appropriate water content,so that air entered the substrate to ensure the root respiration and normal growth.The second period was the flushing stage,and there was no flushing stage under normal irrigation mode.The water contents in the coco coir slabs were kept at the appropriate range,and a certain irrigation-to-drainage ratio maintained,to benefit the root growth of tomato and absorption of nutrients,and solved the drought stress caused by insufficient irrigation and nutrient waste caused by too much irrigation.The effect of the transpiration feedback intelligent irrigation system was tested,and an irrigation system controlled by light radiation accumulation which was designed by the RIDDER company in the Netherlands was selected as control.The results showed that the irrigation amount of the transpiration feedback irrigation system increased by 9.4%compared with the control,the drainage decreased by 18%,and the drainage EC value was stable.Compared with timed irrigation,the amount of irrigation was reduced by 32%and the amount of drainage was reduced by 57%by using the transpiration feedback irrigation system,and more nutrients were absorbed and utilized by tomatoes.There were no significant differences between the fruit yield,plant height,and node number of the tomato by using the transpiration feedback irrigation system and those by using the irrigation system designed by the RIDDER company.Under the condition of 10 years of the design life of irrigation system in 5000 m^(2) greenhouse,compared with the application of the irrigation system designed by the RIDDER company,the annualized cost of the intelligent irrigation system designed by this study was 20.8%lower than that by using the irrigation system designed by the RIDDER company.The transpiration feedback intelligent irrigation system could meet the requirements of automatic precision irrigation,and if the irrigation control model might adjust according to the substrate characteristic,the system could also be used for automatic precision irrigation of the Rockwool cultivation,the mixed substrate potted cultivation,and other soilless culture.