Odysseys of agriculture sensors: Current challenges and forthcoming prospects
Introduction
Innovation in science and technology has often brought dramatic changes in human civilizations. For instance, discovering the art of alloy making by Sumerians in the third millennia B.C. gave them a superseding capability than their neighbors who merely use stone weapons for their food hunting (Singh et al., 2015). The weapons made from the metal alloys have better shape, design, and were handy. These design considerations assisted them to adapt better and hunt their food quickly. These better-equipped tools allowed the barbarian and nomadic sects to settle down at a place for quite a long time. Historically, agriculture began as an outcome of the transition from hunter-gatherer to agricultural societies. The modern agricultural societies we see today is an outcome of a long term evolutionary process of socioeconomic significance (Svizzero and Tisdell, 2015, Zvelebil and Pluciennik, 2011). Nevertheless, there is no precise date in history to determine the exact origin of agriculture, but the impact of agricultural evolutions in establishing modern society cannot be underestimated. The significant changes brought by the inception of agriculture are the stabilization of hunt gatherers to a family that gradually transformed into a community, more prolonged survival of infants, better safety, and progress in better human health. Contrary to this, there are disadvantages associated with them as density-dependent diseases and other pathological conditions relating to poor diet (Zvelebil and Pluciennik, 2011). In summary, though agriculture allowed an increase in survival, it was the industrial revolution (Allen, 1994, O'Brien, 1977, Zambon et al., 2019) that offered people to lead a healthy life. The rise of the industrial revolution has given agriculture to shoot up, yet tremendous technological advances have yet to come to meet modern rising expectancies from agricultural products.
Modern agriculture is an outcome of various socio-economic changes that took place over several thousand years back. Through years, agriculture has been a significant backbone and a source of food production for millions of growing populations across the globe. In a recent report from the food and agriculture organization of the UN (FAO) human population is expected to touch 9.2 billion by 2050 and the food production must increase by 70% to meet the asking food consumption (Alexandratos and Bruinsma, 2012, Basnet and Bang, 2018). The growing limits of food production for paced populations has invited several debates and preoccupations for decades. A few critical debates which gathered mass attractions are a church leader Tertullian in 3rd century CE, followed by Malthus in late 8th century CE (Hardin, 1998), and recently by Paul Ehrlich’s who coined the famous terminology Population Bomb (Alexandratos, 1988). Statistics say that there was sufficient food for each person 2770 kcal/person/day in 2005/2007, but the condition will entirely be different in 2050. These statistics unfolds from the fact that global GDP will be just 2.5 folds, whereas the population is going explode in the coming years if no checks and strict rules are framed in the developing countries to curb populations. Though the jurisdiction of this review lies outside to put any opinion on the measures and regulations that must be taken by various countries to control population explosions, indeed, the growth and pace at which modern agriculture will look like in the coming few decades have a one-to-one relation with it.
Agriculture in developing countries must undergo a significant transformation to meet growing populations (De Bon et al., 2010). Ensuring food to paced growth populations will require faster growth in the agriculture outputs than the previous decades. Eventually, there are certain unavoidable restrictions such as impounded climatic changes, reduced rainfall, changes in temperature, and precipitations are bound to reduce agricultural productivity and make production more erratic (Cline, 2008, Fischlin et al., 2007, Lobell et al., 2008, Parry et al., 2007). Specific methodologies are suggested to improve the yields of agricultural outputs, namely: climate-smart agriculture (CSA) followed mainly in countries like Malawi and Zambia (Sanchez et al., 2009), conservation agriculture (CA) again practiced in Zambia, Smartphone-based sensors in agriculture (Pongnumkul et al., 2015), and microelectromechanical systems (MEMS)-based agriculture (Dell et al., 2009, Wang et al., 2018a).
This review has a circumference of the sensors used in agriculture. However, we will be slightly more inclined to MEMS-based sensors in this review, will try to introduce the mechanism of MEMS sensors, bring a picture of recent developments made till date, and at the same time will raise a few inevitable challenges in the upcoming agricultural methodologies. Moreover, we will also elaborate on the significant problems in data acquisition, their solutions, and will also focus on their performance enhancements. The interest in MEMS-based sensors is an obvious choice, as evident from the market potential and the enormous revenue MEMS-based sensors have generated during the past few years, as shown in Fig. 1. Furthermore, we will also try to address a few unmet issues prevailing in the agriculture sensors, will figure out the possible solutions, and we will present our viewpoints to address them. More significantly, we believe that this extensive review will offer and attract readers from different backgrounds and will give them a new window to look at and design agricultural sensors for better productivity.
The MEMS acronym stands for the microelectromechanical system, introduced in 1986 for the first time; since then, millions of such devices have been introduced in the market and are commercialized daily (Valente, 2017). MEMS can be seen exhaustively in the fields of printer heads in ink-jet printers, projection systems, drones, game controllers, microphones, digital cameras, smartphones, biosensors, optical sensors, lab-on-Chip, accelerometers, and gyroscope are to name a few. Their ubiquitous nature owes to their compactness, robustness, precision, and lower production cost. Though the application of MEMS in automobiles, health care, and consumer goods have seen unprecedented developments, their applications in the field of agriculture lie only as a secondary option in the form of MEMS in drones and a few cases in agriculture accelerometers. Thus, the use of MEMS sensors in the field of agriculture is not only novel but also exciting as it can open new dimensions to agriculture in the form of precisions agriculture (PA) (Barnes et al., 2019), seed sowing, and crop harvesting. With the introduction of PA, the whole field is used as a sector to increase productivity (Balafoutis et al., 2017) and thus increase profitability in parallel with the internet-of-Things (IoT). The marriage of IoT and MEMS-based agricultural sensors is sure to bring enormous benefits to agricultural productivity in the coming years.
Though MEMS works on the principle of different domains such as piezoelectric, electromagnetic, electrostatic, and thermal, etc. (Valente, 2017), but here we try to present the most acceptable working principles of MEMS sensors. Whenever a tilt is applied to the MEMS sensors, the previously balanced mass now makes a difference within the potential, and this is measured by a position measuring interface circuit. This measurement is converted then into digital signals with the help of analog-to-digital converter (ADC) for digital signal processing. At this stage, it is also advantageous to define few other related devices that will be used in parallel to MEMS, such as gyroscope-is a device that is capable of measuring both the displacement of the resonating mass and its frame due to Coriolis acceleration (Shakur and Kraft, 2016). Furthermore, MEMS are considered to be inertial sensors. Inertial sensors mean, they have a mass that resonates whenever a tilt is given to the MEMS sensors.
A body constituting a mass is bound to be governed by Newtonian equations and its laws of motion and MEMS are not an exception to it.
Newton's second law of motion can be stated as acceleration (a: m s−2) of a body is directly proportional to the force (F: Newton/N) applied and in the same direction as force and inversely proportional to the mass of the body (m: kg).
It is essential to understand at this point that acceleration always creates a force that is eventually captured by the force-detection mechanism of the accelerometer. Thus, an accelerometer measures a force and not acceleration; however, one receives an acceleration when it is actually applied to any of the accelerometer axes.
Section snippets
Fundamental mechanism of accelerometer
Fig. 2a illustrates the basic mechanism of an accelerometer and its capacitance relation to the moving mass and the piezoelectric technique based in Fig. 2b. An accelerometer mostly relies on measuring accurately the capacitance generated by the acceleration in relation to the moving mass. The other type of accelerometer is based on the piezoelectric phenomenon (Gesing et al., 2018). Accelerometer working on this mechanism constitutes a set of two plates one fixed and another mobile. One or
Sensors in agriculture
In this section, we will focus on the recent developments made in the direction of agriculture sensors based on their design considerations, applicability, and accuracy. For the sake of simplicity, we bifurcate the agriculture sensors based on the agriculture conditions and agriculture products. In the sections of agriculture conditions, we will address soil, environment, weed control, seed, seedling, and many other components, whereas, in the production section, we will be involved in the
Other MEMS sensors
There are several other MEMS-based sensors used in agriculture and discussing them here in a single review would be an injustice them. Thus, to have a flavor of their application area and to give the reader a platform to explore more about them, we will try to introduce a few prominent ones in this section. A recent study deployed a MEMS-based sensor to evaluate the force generated by a growing root (Hida et al., 2014). This device consists of a V-shaped groove to incorporate the growing root
Outlook and future prospects
The development of a MEMS-based sensor brought a resurgence of interest in the agriculture sector. MEMS-based sensors allow the manufacturing of economical and effective sensors. From the personal viewpoints and the status of literature published in this direction up to now suggests a few hurdles and strategies that must be considered seriously in the direction of further developments to engage MEMS sensors in agriculture. The following steps are vital to the realization of MEMS-based
Conclusion
In this review, we have tried to accumulate the long journey sensors have traveled to shape themselves in the form of MEMS-based agricultural sensors. In this review, we put forth an unbiased view on the conventional and recent sensors being used in the field of agriculture. At some point of discussion, we have also discussed in parallel about traditional and modern sensors. This review consolidates a variety of sensors spanning from soil moisture sensor, air humidity sensor, leaf moisture, sap
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
We would like to express our sincere thanks to valued reviewers, whose feedback and suggestions helped this review to improve its quality significantly. The author sincerely thanks the various publishing house for allowing a hassle-free permission process for the figures to be used in this review.
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