# Monitoring Citrus Soil Moisture and Nutrients Using an IoT Based System
## 3 Design Scheme
### System Software Design  
Citrus soil, temperature and nutrient monitoring system is the core of the system. Its architecture is shown in Figure 5 below. In this section, the permission management module can assign different permissions to different roles. In the sensor network management module, users can manage sensor network nodes and view the sensor status. The data query and analysis module based on WEB GIS can check the spatial distribution of soil moisture, temperature and nutrient. The decision-making system in the decision support module of citrus precision fertilization can make decisions according to the soil moisture and temperature. If the system decision-making model is not ideal, it will be modified or replaced to adjust the expert decision-making advice in a short time. It is the management module function of the decision model. Data management mainly includes data receiving, data storage and data processing. In order to make users more intuitive to observe the effects of temperature, humidity and nutrient and other parameters on citrus growth, providing the basis for scientific cultivation, citrus soil temperature and nutrient monitoring center drawn curves for different functions on the sensor upload data. Users can query the environmental parameters monitored by the sensor nodes at different locations and at different times. Figure 4: Spot main control node structure. The decision support module is one of the most important parts of the system, and other modules provide supports for it. The model management module includes the expert knowledge base of citrus fertilization and irrigation, and allows the authorized users to revise and supplement the knowledge base according to the actual situation. The data management module processes and analyzes the collected data. It ensures that these data meet the data input format of the model. We use the single-point multi-layer detection method when using sensors to obtain soil moisture, temperature and other environmental conditions. The application of this method makes the grower have a more comprehensive and accurate grasp of citrus growth environment status, while improving the accuracy of fertilizer and irrigation decisions. Take the citrus orchard soil moisture monitoring as an example, for the same fruit tree the water content at 20 cm, 40 cm and 60 cm below the surface will be monitored. The three humidity values of different surface depths are averaged as one of the input conditions of the irrigation decision system. Table 1 shows some examples of expert knowledge bases for citrus irrigation in sandy soil types. An irrigation decision-making system based on soil properties, the average water content and time stamp gives reasonable irrigation decisions. The citrus intelligent irrigation decision-making system process is shown in Figure 6.  
Figure 5: Software architecture of citrus soil temperature and humidity monitoring system. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Soil Properties** & **Humidity (\%)** & **Season** & **Diagnostic Conclusion** & **Expert Advice** \\ \hline \multirow{8}{*}{\(<\)17} & \multirow{8}{*}{spring} & \multirow{8}{*}{Incremediately carried out winter irrigation. first build the hillock in the crown to form a water plate, Irrigate 20 kg per square meter of canopy projected area. One migration water hole 2-4 in the drip line around the crown, Irrigate 10 kg per square meter of canopy projected area.} \\ \cline{1-1} \cline{3-5}  & & & & Immediately carried out winter irrigation. first build the hillock in the crown to form a water plate, Irrigate 10 kg per square meter of canopy projected area. enough project area. Drug irrigation water hole 2-4 in the drip line around the crown, Irrigate 7 kg per square meter of canopy projected area. enough water is given to the tree tray before the frost. \\ \cline{1-1} \cline{3-5}  & \multirow{2}{*}{\(<\)18} & \multirow{2}{*}{summer} &