# Smart Irrigation Systems from Cyber-Physical Perspective: State of Art and Future Directions
## 2 Overview of Irrigation Technology  
Irrigation water can be sourced from diverse sources, including groundwater obtained from springs or wells, surface water drawn from rivers and lakes, treated wastewater, drainage water, or even collected fog. Since 2017, with the rapid advancements in IoT and AI technologies, agriculture has developed into Agriculture 4.0, also called Smart Agriculture, which includes smart irrigation systems.  
There are four major types of irrigation systems: (i) _Surface irrigation_, the oldest form of irrigation, is also called \"gravity irrigation\", which uses the gravity of water to design the irrigation system. Surface irrigation is the first engineering innovation humans have. (ii) _Sprinkler irrigation_ refers to how water is pushed to the central locations and distributed to different places through high-pressure water devices. (iii) _Micro-irrigation_ refers to the one that distributes water under low pressure via prearranged networks to each plant. (iv) _Drip irrigation_ sends water to the root zone of plants directly with various dripping methods [22; 23].  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Survey ID** & \multicolumn{2}{c}{**IoT Layers**} & \multicolumn{2}{c}{**Environment Factors**} & \multicolumn{2}{c}{**Business Dimension**} & \multicolumn{1}{c}{**Others**} & \multicolumn{1}{c}{**Year**} \\ \hline  & **Perception** & **Network** & **App.** & **Field** & **Natural** & **Crops** & **Cost/Energy/Water** & & & \\  & & & **Cond.** & **Var.** & **Crops** & **Util.** & & & \\ \hline
[3] & LoRa & LoRaWAN & Monitoring & No & No & No & partial & No & 2023 \\ \hline
[4] & Yes & Yes & Yes & Partial & Partial & Yes & No & & 4 layers (physical & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\ \hline
[5] & Yes & Yes & Yes & Partial & Yes & Yes & No & & 4 layers (physical, & \\  & & & & & & & & & network,, decision, app) & 2021 \\ \hline
[6] & Partial & Partial & AI & No & No & No & Partial & AI tech & 2019 \\ \hline
[7] & Yes & Yes & Partial & No & No & No & Partial & 4 layers (IoT, Edge, Fog, Cloud) & 2021 \\ \hline
[8] & No & No & Yes & No & Yes & No & No & & 4 layers (perception, & \\  & & & & & & & & & transport, processing, & \\  & & & & & & & & & app) & 2019 \\ \hline
[9] & Yes & Yes & Yes & No & No & Partial & No & & 5 layers (physical, & \\  & & & & & & & & network, middleware, & \\  & & & & & & & & & service, app) & \\ \hline
[10] & Yes & Yes & Yes & No & No & No & Yes & Greenhouse & 2022 \\ \hline
[11] & Yes & partial & Yes & No & No & No & Yes & Smart agriculture & 2019 \\ \hline
[12] & No & No & Monitoring & No & No & No & Partial & Application layer  
Among the four primary types of irrigation systems, surface irrigation is the least efficient, with an efficiency rate of 60%, whereas drip irrigation is the most efficient, achieving a rate of 90% [24]. Despite its inefficiency, surface irrigation remains the predominant method, constituting 85% of all irrigation techniques. This method results in nearly 40% of water wastage, especially in countries such as India and China [1]. Conversely, although micro-irrigation and drip irrigation systems are more efficient, they have been less studied, which is primarily due to their higher setup and maintenance requirements. As a result, most of the literature focuses on surface and sprinkler irrigation systems rather than drip or micro-irrigation systems.