# A Review of Practice and Implementation of the Internet of Things (IoT) for Smallholder Agriculture
## 3 Results and Discussion
### Current State of IoT for Agriculture
\begin{table}
\begin{tabular}{c c} \hline \hline
**Sensor Type** & **Agricultural Parameter** \\ \hline Electrical capacitance & Soil moisture [30; 31; 32; 33; 34; 35], ambient humidity [36; 37] \\ \hline Electrical conductivity & Soil moisture [38; 39; 40], soil and water pH [41], ambient humidity [34; 42] \\ \hline Load cell & Weight of harvested crops [43; 44], crop waste [45] \\ \hline Electrochemical & Ethylene concentration in crop storage [46], greenhouse CO\({}_{2}\) concentration [47; 48], beehive monitoring [49] \\ \hline Optical & Crop height measurement [50; 51], livestock and predator monitoring [52], volume of harvested grain [53], plant mapping [54], NDVI [55], soil composition [56; 57; 58], N content [9; 10; 59], solar irradiance [60], plant disease detection [61], crop waste [45] \\ \hline Thermocouple, thermistor & Seed and crop storage [62], greenhouse monitoring [34; 48; 63], soil temperature [34; 64], water temperature [65] \\ \hline Pressure and flow rate & Irrigation water flow [66], handpump usage [67] \\ \hline Acoustic & Animal detection [68; 69], water level [70], grain silo level [3] \\ \hline Accelerometer & Livestock monitoring [71; 72], crop transport [73], handpump usage [67] \\ \hline Magnetic flux & Electrical current and power consumption [74] \\ \hline RFID & Livestock and poultry tracking [75; 76], supply chain tracking, asset tracking \\ \hline GPS & e-Extension [77], equipment navigation, livestock tracking [76; 78], wireless fencing, asset tracking [79] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sensor types and corresponding agricultural parameters. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Protocol** & **Description** & **Advantages** & **Disadvantages** \\ \hline Zigbee & IEEE 802.15.4-based specification using mesh network topology and suitable for short- to medium-range & Long battery life (node sleep mode) & Short range (10-100 m) \\  & & \(>\) 65,000 nodes in a mesh network & Incompatibility with other protocols \\  & & \(>\) 65,000 nodes in a mesh network & Signal interference in \\  & & \(\text{License-free frequency band}\) & 2.4 GHz band \\ \hline Z-Wave & Mesh network protocol that uses low-energy radio waves and proprietary radio system & Devices are interoperable & Max 232 nodes in a mesh network \\  & & \(\text{Suitable for low-power}\) devices & Not suitable for high-power devices \\ \hline LoRa (Long Range) & Long-range, low-power, and low-bitrate protocol that uses storage topology and unlicensed & Long range (10 km) & Actual line-of-sight range of \(\sim\)2 km \\  & & \(\text{Low power consumption}\) & Large bandwidth for data transmission \\ \hline WiFi & IEEE 802.11 standards used for the wireless communications of short-distance local area networks & Broad device support Easy setup Inexpensive & Short range (\(\sim\)20 m) \\ \hline Bluetooth Low Energy (BLE) & Wireless personal area network with low power consumption and cost & \(\text{License-free 2.4 GHz band}\) & Low bandwidth Short range (\(<\)100 m) \\  & & \(\text{Frequency-hopping reduces}\) signal interference & \\ \hline SigFox low-power wide area network (LPWAN) & Proprietary service tailored to IoT networks in a star topology operating on unlicensed ISM frequency band & Low power consumption Low-cost because the network and computing complexity is managed in the cloud & Not supported in all countries Susceptible to signal interference in some countries \\ \hline Cellular & Network distributed in “cells” served by a fixed location transceiver. Most use star topology & Broad device support Available globally with large and growing infrastructure & Bandwidth can be limited due to network traffic High power \\ \hline \hline \end{tabular}
\end{table} 
Table 2: IoT data transmission protocols. Figure 5: Range vs. data rate for common communication protocols [81]. Even though many organizations in LMICs have developed IoT systems for agriculture, few studies have reported on the implementation in a smallholder context and associated outcomes.