Internet of Things-based Hydroponic: Literature Review

Hydroponics is a method of growing crops without using soil, with the benefits of controlling the environment and nutrients, conserving water, and reducing labor. The applied technology is used to improve results that have consistency. This research was conducted with the aim of knowing the IoT devices and platforms used in the development of IoT-based hydroponics. Data obtained from the website garuda.ristekbrin.go.id and www.sciencedirect.com from 2016 to 2021. This study is a literature review using the PRISMA method. This method is used for literature review using a systematic and structured basic framework. The results of this study indicate that the variables measured are Temperature, Potential Hydrogen (pH), Total Dissolve Solid, Water Temperature, Humidity, UV, Carbon Dioxide, Soil Moisture and Electrical Conductivity. The device used is the ESP8266, Arduino, and Raspberry PI with the MySQL, Thingspeak, Firebase, Domoticz, and Wyliodrin IoT Platforms.


Introduction
Farming is a human habit that has existed since time of immemorial. This farming activity has also changed along with the development of technology. Changes in farming activities due to technological developments exist in various aspects. Starting from the purpose of the farming activity itself, changes in plant types to changes in planting methods. One of them is the method of farming using hydroponics.
Hydroponics is a method of growing crops without using soil as a growing medium, but using nutritious water or materials containing nutrients [1]. Hydroponics itself comes from the Greek "Hydroponos" where hydro means water and ponos means power [2]. With the hydroponic planting method, the use of environmental control, nutrition, and water conservation can be directly carried out and periodically observed by farmers.
This hydroponic method can be done vertically in a narrow space such as a yard or terrace so it does not require a large space. The requirements for hydroponic growing media are: (1) water absorbant, (2) air circulation, and (3) cheap [2].
The advantages of cultivating plants using this hydroponic method include: (1) producing products that are superior in quality and quantity to conventional cultivation, (2) lower plant pests and diseases, and (3) easily control the nutrients provided [3].
Although there are many advantages and conveniences created by the hydroponic method, in the conditions of the covid-19 pandemic, there are still many farmers that use conventional methods of farming. This is because the hydroponic method is considered the same as the conventional farming method which must be controlled directly and manually. Therefore, we need a technology-based hydroponic system that can advance agriculture by increasing quantity and optimizing yields and having better quality and making it easier for farmers to control and care for their plants.
Based on developing technology, all aspects of life adapt by applying the latest technology that can provide convenience, including agriculture. Internet of things technology can be applied to this hydroponic system to provide convenience to farmers in carrying out their duties in the midst of the COVID-19 pandemic. The conveniences obtained from the application of the IoT in hydroponic farming activities include monitoring and controlling activities as well as plant care that can be done anywhere and anytime.

Methods
This research is a systematic review research using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) method. PRISMA is a literature review method using a systematic and structured basic framework. The procedure of this research method consists of several stages, namely: 1) Preparing the background and research objectives, 2) Formulating research questions, 3) Searching for literature, 4) Selecting literature according to the criteria, 5) Practical screen, 6) Data extraction, and 7) Data synthesis [4].

Object of the Research
In this study, the object are research journals on IoT-based hydroponic methods based on the following reasons: 1. There are several additions to the IoT system in the hydroponic farming method that can assist farmers in monitoring and remotely controlling the plants being cultivated. 2. An IoT-based hydroponic system that is implemented using a specific microcontroller. 3. IoT-based hydroponics has a variety of protocols that can be customized as desired. 2.2.6. Data Analysis. Based on the results obtained at the data extraction stage, the next procedure is to perform data analysis which includes an explanation of the following points: 1. Variables measured in the development of an IoT-based Hydroponic system. 2. Devices used in the development of IoT-based Hydroponic systems. 3. The IoT platform used in the development of an IoT-based Hydroponic system.

Search and Selection Process
Based on the search process using the keywords hydroponics and internet of things on the garuda.ristekbrin.go.id website page, 16 (sixteen) and only 7 (seven) journals met the following inclusion and research induction criteria. From the website www.sciencedirect.com obtained 99 (ninety nine) titles of scientific writing using the keyword hydroponic internet of things. Then from the 99 (ninety nine) titles, 50 (fifty) titles are obtained which are research articles. After the review, 20 (twenty) journals of research articles were found that were accessible and the journals met the inclusion criteria and research induction as follows.

Quality Assesment Result
The journals that have been obtained were selected according to the quality assessment criteria referring to QA1, QA2, and QA3, so that the data in Table 3 and 4. is obtained below.
Based on the data table 3 from the quality assessment results, it is known that there are 3 journals that meet the quality assessment criteria, namely journals number 2, 4, and 6. Meanwhile, two journals did not meet the quality and there were two journals that could not be accessed completely so that it was not possible to know their eligibility to be used in this study.