## 3 Major Agriculture Applications and Services
### Soil Monitoring  
Soil plays a critical role in plant growth. It is necessary to monitor the soil at the field scale. By obtaining the soil's health information, a grower can make fruitful decisions at different plant developmental stages. The main objective of soil analysis is to measure the content of nutrients present in the soil, which ultimately leads to many treatments to fulfill the level of nutrients. Remarkably, the soil test is suggested annually in the spring season; however, it can be changed according to the local environmental conditions and  
Figure 2: Major applications, services, and sensors for advanced agriculture, modified from [PERSON] et al. [26]. conducted in the winter or autumn season [27]. Several soil factors, such as soil types and soil moisture, are recommended to analyze and quantify fertilizers and irrigation requirements. These primary factors also help provide information regarding the other vital factors, including physical, chemical, biological ones. The soil map helps to identify areas with good soil health and texture for the suitability of seeds, sowing time, and even sowing depth because some plants have deep roots and others have shallow root depths. Many researchers have recently developed tools, technologies, and devices to monitor soil health. These new tools are the major resources for farmers and growers, which can be used to monitor soil features such as water holding capacity, moisture, chemical, and physical properties. These tools also help monitor soil health, such as salinity, pH, soil organic carbon (SOC), electrical conductivity (EC), nitrogen, potassium, and phosphorus, which help estimate required fertilizers. One of the latest tools introduced by Agro Cares is the Scanner and Lab-in-box, which is known as a laboratory, having complete information by services through which it gives soil status information [28]. This is the modified tool used by many farmers without any laboratory for sample analysis. This tool can analyze about 100 soil samples daily. One of the major issues for estimating crop water requirements is continuously monitoring soil moisture. To monitor soil moisture, in situ soil moisture sensors, remote sensors, and tools can be efficient strategies for many farms to obtain information about the soil's moisture. There are many satellites in operation to measure soil moisture data at a global scale. These remote sensing products are: (i) the Advanced Microwave Scanning Radiometer Earth Observing System (AMSR-E) (2002-September 2011); (ii) the Soil Moisture Ocean Salinity system (SMOS, 2010-present); (iii) AMSR2 (2012-present); and (iv) the Soil Moisture Active Passive system (SMAP, 2015-present) [29]. For example, Soil Moisture and Ocean Salinity (SMOS) was launched in 2009 and started to monitor soil moisture from May 2010 globally. In addition, in situ wireless soil moisture sensors can also monitor soil moisture at the farm scale. New tools, including the vision-based and wireless sensors, are used to determine crop factors, such as soil depth, for efficient seeding processes. Several robotic tools are developed for smart farming and improve crop production, such as FarmBot and Agribots, just to name a couple. In agriculture practices, such as sowing seeds, weeding, fertilizing, and irrigating, such tools would help improve crop production if it is implemented at a large scale. Agribots is a type of robot; the agriculture field's location is determined by pairing digital computers with the vehicle vision system. This type of robot works on any agricultural land in which the global positioning system (GPS) helps develop location maps. Sensors that are mounted with light-emitting diodes (LEDs) help provide information regarding the flow rate of seed. Many remote sensors are used for this purpose [30]. These LEDs are the source of receiving radiations that have visible and infrared light waves. Seed movement is monitored through many elements, including light band, voltage output, and receiving element.