A Smart Monitoring Service for Irrigation The current irrigation method of using WSN is new (K. H. Dhara and A. B. Makwana, 2015; Loubna Hamami et al., 2020), however the farmers have not yet fully embraced it. It is mostly used by researchers to carry out experimental experiments. A novel idea in agricultural applications, the wireless sensor network (WSN), inspired several academics to do study in this area. The current irrigation method of using WSN is relatively new but holds immense potential to revolutionize agriculture through its real-time monitoring and precision water management capabilities. Wired sensor systems may now handle particular challenges thanks to recent advancements in wireless sensor network (WSN) technology (Md Mohinur Rahaman et al., 2022; Mehdi Gheisari et al., 2022). Wired sensor systems may now handle specific challenges thanks to recent advancements in wireless sensor network (WSN) technology (A. Z. Abbasi et al., 2014).
3.1 Soil Evaporation Model
Prediction of soil moisture is essential for effective irrigation management. The Penmen approach was thought to produce the most precise findings with the least amount of inaccuracy in relation to the live grass reference crop. It was found that, depending on the location of the land, the pan approach would provide us with appropriate precision. The following equations illustrate the FAO Penman-Monteith technique for calculating ET0:
where ET0 = reference evapotranspiration (mm day−1), G = heat flux density of soil [MJ m−2·day−1], μ2 = wind speed at height of 2 m [ms−1], T = daily mean air temperature at 3 m height [°C], Rn = crop surface net radiation [MJ M−2 day −1], ea = actual vapor pressure [kPa], es = saturated vapor pressure [kPa], es-ea = deficit saturation vapors pressure [kPa], P = atmospheric pressure [kPa], Δ = curve of slope vapor pressure [kPa °C−1], γ = psychrometric constant [kPa °C−1], z = elevation above sea level [m], e0 (T) = saturation vapor pressure at the air temperature T [kPa], CP = specific heat at constant pressure, 1.013 10–3 [MJ kg−10C−1], λ = latent heat of vaporization, 2.45[MJ kg−1], € = ration molecular weight of water vapor/day air = 0.622.
The soil moisture estimation is mainly depending upon the evapotranspiration. The other most frequently used method based on extra-terrestrial radioactivity and temperature to evaluate ET0 (G. H. Hargreaves and Z. A. Samani, 1985)
where ET0 = reference evapotranspiration (mm/day), Tmax and Tmin = max. temperature and min. temperature (°C), Ra = extra-terrestrial radiation (MJm−2 day−1).
Ritchie purposed another method for the estimation of ET0 (C. Jones, 1990) based on solar radiation and temperature. It is expressed as
where ET0 = reference evapotranspiration (mm/day); Tmax and Tmin = maximum and minimum temperature (°C); and Rs = solar radiation (MJm−2 day−1).
When
A method for measuring evapotranspiration based on neurofuzzy (NF) inference was developed because it shows greater accuracy than combinations of air temperature, wind speed, and solar radiation (M. Cobaner, 2011). The NF model is dependent on relative humidity, solar radioactivity, and air temperature. The weather forecast sensors installed at the farm have anticipated the wetness of the soil. According to L. Ruiz-Garcia (2009), soil temperature, radiation, air temperature, and relative humidity all affect how much moisture evaporates from the soil. In order to efficiently irrigate farmland, a sensor-based and IoT constructed architecture (Figure 4) has been developed for gathering, processing, and transmitting the various physical parameters (air temperature, air relative humidity, soil moisture, soil temperature, and radiation).
3.2 WSN Architecture
The mobile ad hoc network of WSNs, access points, routers, gateways, and multi-point relays shown in Figure 2 form a sophisticated architecture for seamless communication and connectivity among WSN nodes, coordinators, relays, gateways, and routers. As highlighted by Mir A et al. (2002), Rathore M et al. (2018), and P. Singh et al. (2013), access points serve as fixed-point transceivers, granting local nodes or those within wireless range easy accessibility. Meanwhile, multipoint relays play a vital role in establishing connections to various networks, including the Internet and mobile service provider networks. When it comes to packet transmission, routers skillfully navigate through available open paths in the network, efficiently choosing the optimal route. Lastly, the crucial task of linking the two networks falls to the coordinator, ensuring seamless communication between them. This intricate architecture forms the backbone of the smart monitoring service for irrigation, allowing real-time data collection and analysis for precise water management in agricultural fields (Jazaeri et al. (2021).
The WSN nodes have the ability to forward data to the access point (base station) as well as sense data. The nodes may move around and can communicate with distant access points while having coverage and mobility range. Access points have the ability to acquire and process data and are connected to a wider network, such as the Internet (Kenny Paul et al., 2022; S. M. Kamruzzaman et al., 2019). Layered construction is seen in Figure 3. Each node has a connection to a close neighbour. When the node travels farther, it connects with the access point (base station) through 2 or 3 hops. Low-power transceivers connect each node to the closest neighbouring layer WSNs.
Assume that there are three levels of WSNs around the base station. WSNs at Layer 1 link directly. Before connecting directly, layer 2 WSNs make connections to layer 1 WSNs acting as coordinators. Prior to connecting to layer 1 WSNs and the access point, layer 3 WSNs establish connections to layer 2 WSNs serving as coordinators. The layer 1 WSN1 and WSN6 connections to the access point are depicted in the image. It denotes a hop count of 1. WSN 2 and WSN 3 are likewise depicted in the picture at layer 2. The first hop is to WSN1, while the second hop is through WSN1. For layer 2, the hop count is 2. In other words, WSN 2 is connected to WSN 1, which is connected to the access point (base station).
WSN 4 and WSN 5 are likewise depicted in the picture at layer 3. Three hops are required for their connection—one to layer 2 WSN, one to layer 1 WSN, and one to the access point. For layer 3, the hop count is 3. As a result, WSN 5 connects to WSN2, WSN1, and finally the access point. The access point is connected via WSN4 before WSN3, WSN1, and WSN3. Wireless LAN (802.11b) access points are used to link the clusters. Connectivity to the Internet is made possible via the access points. Users with mobile devices and distant clients can access the archived and real-time queryable sensor data. The WSNs are shown in Figures 2 and 3. Every access point and gateway are connected. Each gateway uses LPWAN to interact with the cloud.
3.3 Proposed System Architecture
The fundamental design of a wireless sensor network-based irrigation monitoring system is depicted in Figure 4. The sensor nodes, gateway node, cloud, and Internet are the system's four key parts.
Sensors: The tools that gather environmental data are known as sensors. Temperature, humidity, soil moisture, and light intensity sensors are all present in this situation. The gateway devices receive the wirelessly sent sensor data and pass it along to the cloud computing platform for processing and analysis. This information may then be used by the cloud computing platform to decide when and how much to irrigate the crops. The platform may also transmit instructions back to the gateway components to regulate the irrigation system.
Gateway: A device known as a gateway is used to gather data from sensors and transmit it to a server. A Wireless Sensor Network (WSN) module, a WiFi module, a microcontroller unit (MCU), and RAM are all included with the gateway.
Server: The server is the key element of the system that stores and processes the sensor data. It receives the data from the gateway and, after analysing it, issues orders to the actuators.
Devices that carry out activities in response to orders sent from the server are known as actuators. The actuators in this instance consist of a water pump, a solenoid valve, and a fertiliser dispenser. The MCU in the gateway, which gets commands from the server through the WSN module, manages these devices.
A WSN has an ID and monitors moisture among other things. Every node is a WSN. Each WSN takes measurements at certain depths inside the soil at designated locations within a crop. Three similarly spaced depths of sensors are employed. A network is created when a collection of WSNs use ZigBee to communicate. Each network has an access point that uses LPWAN to receive messages from each node.
Data is continually gathered by the sensors and sent to the gateway. Data from the sensors is gathered by the gateway and sent to the server via the WiFi module. To ascertain the plants' watering needs, the server receives the data and processes it. The server issues orders to the actuators based on the analysis to carry out the required tasks, such as turning on the water pump or opening the solenoid valve. Through the WSN module, the server sends commands to the MCU in the gateway, which then uses those commands to operate the actuators.
The smart irrigation monitoring system we suggest carries out the following duties:
- Smart irrigation uses moisture sensors and actuators to water channels.
- Installs each soil moisture sensor at a certain depth in the fields using a sensor circuitry board.
- Makes use of a variety of actuators (solenoid valves) that are positioned along water lines and that regulate moisture levels that are too high during a certain crop time.
- Monitors evapotranspiration (evaporation and transpiration) and moisture in fruit plants such as grapes and mangoes using sensors positioned at three depths.
- Calculates and tracks real water requirements for irrigation and absorption
- Each sensor board is enclosed in a waterproof shell and uses the ZigBee protocol to connect to an access point. A WSN is made up of a number of sensor circuits.
- The data is received by the access point, which then sends it to a related gateway. Data is transformed at the gateway before being sent through LPWAN to a cloud platform.
- The platform's analytics examine the moisture data and interact with the water irrigation channels' actuators in accordance with the amount of water needed and previous data.
- Sensors take measurements at predetermined intervals, and actuators respond to the intervals' needed values after analysis.
- The platform sets the preset measurement intervals of T1 (for example, 24 hours) and the preset actuation interval of t2 before uploading the programmes to the sensors and actuators circuits.
- An algorithm downloads and updates the programmes for the gateways and nodes. Sensed moisture readings that surpass certain thresholds then send off the alert.
- Operates at the data-adaptation layer and, at regular intervals, identifies the malfunctioning or inaccessible moisture sensors.
- The monitoring system's prototype was created using an open-source SDK and IDE.
3.4 Experimental Setup
Typically, the experimental setup for the Smart Irrigation Monitoring Service utilising Wireless Sensor Networks (WSN) consists of a network of sensors that monitor soil moisture content, temperature, and humidity levels. The sensor nodes are wirelessly linked to a central node or gateway, which is in charge of gathering data from the nodes and transmitting it to a platform for cloud-based data storage. Figure 5 displays photographs of the planned model prototype that was placed in several agricultural areas to gauge the soil's temperature and moisture content.
To operate the hardware, a software programme is created and run on the ESP8266 microcontroller. The node was positioned close to the plant to feel its surroundings, and it is wirelessly connected to the main station through an ESP8266 microcontroller that serves as both an access point and a server. The ESP8266 module also communicates with the main station via serial communication. Each zone in the planted area has sensors for soil moisture, air humidity, air temperature, and solar light brightness. To obtain correct data, this division is carried out depending on the sensing range of the sensors. The ESP8266 module is used to wirelessly link all the parameters that correspond to the defined zone before sending them to the sink node. After that, each sensor node's data is assembled and delivered via serial connection from the sink node to the main station. The main station collects the data and uses an application to process it in order to decide on irrigation while simultaneously saving the information in a database. The decision command was transmitted through serial connection to an ESP8266 module, then converted and sent wirelessly to the actuator node. The actuator node then uses a relay module to operate the water pumps. Figure 5 depicts the deployment of sensors in various agricultural fields, including farm fields, house gardens, and plant-in-pot fields.
The sensor nodes are positioned across the agricultural area, and the data they collect is evaluated to establish the best watering schedules for the crops. The central node or gateway is often connected to the irrigation system, enabling remote monitoring and management of irrigation procedures. According to studies, using WSN technology for irrigation monitoring has increased irrigation efficiency by an average of 30%. Accordingly, farmers may now use up to 30% less water, which saves them a lot of money and has a less negative impact on the environment.