Perspective Chapter: Mechanization in Agricultural Production from Horizontal and Vertical Perspective

Abstract

The mechanization of agricultural system, both horizontal and vertical cultivation, is imperative for judicious application of resources, reduction in drudgery of workforce, amelioration of productivity and improvement in competitiveness of the produce. However, the reduction in per capita land availability has triggered a mass migration towards vertical cultivation system with heavy reliance towards automation, Internet of Things (IoT) and artificial intelligence. The vertical system of cultivation and protected cultivation system is essential to overcome the limitations of small land holdings, particularly in developing countries and combat global climate change. With the result, the concept of hydroponics, aquaponics, aeroponics is gaining momentum at a rapid pace. The horizontal and vertical system also demands the preparation of organic fertilizer through advanced machinery for bolstering the soil fertility and enhancement in productivity of agricultural crops.

1. Introduction

Agricultural system is believed to have touched ‘tipping point’. The tipping point theory was promulgated as the system is witnessing significant and catastrophic transformation [1] due to the limitations induced by emergence of resistant pests (insects), extreme climatic events, unsustainable land management practices, poor soil conservation measures, attenuation of soil nutrients and global climate change. Many intellectuals believe that the expansion of the agricultural system in the last decade can be attributed to an increase in the production of major crops and cropping intensity as opposed to the expansion in landmass. The contribution of the expansion in the land mass can be as low as 10% [2].

The production of the agricultural crop demands the involvement of mechanical interfaces in the completion of the unit agricultural activities. The mechanization is preferred owing to its involvement in the precision agriculture, automation, post-harvest operations, waste management and organic agriculture, Figure 1. The main objective of farm mechanization is to ensure judicious application of scarce resources, timeliness of the operations, reduction in the drudgery and lowering of input cost in the production system. The reduction in the production cost, directly or indirectly, favours the competitiveness of the produce at local, national and international markets. The production system involves several operations that must be completed within stipulated time to thwart losses and protect the crop from the vagaries of climate.

Figure 1.

Mechanization potential in agricultural production system.

2. Mechanization in horizontal and vertical cultivation system

The mechanization of the agricultural operations is different for horizontal and vertical pattern of cultivation system. In horizontal system, the mechanical interfaces are more or less conventional, operated by prime mover (tractor, power tiller, electric motor, battery) on the levelled ground. In vertical system, most of the systems are protected within the boundaries or the ambient conditions are controlled to simulate the natural conditions. In such a case, the mechanization system is entirely different and demands a systematic approach to balance the mechanization of the horizontal pattern of cultivation.

2.1 Horizontal cultivation system

It is the process of cultivating a crop on a piece of land with the help of different unit operations and utilizing the same piece of land for another crop, when the former is harvested, Figure 2. The horizontal cultivation system is followed across the globe; however, the shrinkage of the land due to rapid urbanization has questioned the sustainability of the horticultural cultivation system. The decrease in per capita land holdings and quantum jump in world population has forced to search for an alternative model. The prediction of 8.3–10.9 billion global population by 2050 [3, 4] with 90% restricted within Asia and Africa has alarmed the scientific fraternity with respect to food security and environmental sustainability. Moreover, there is a steady decline in the productivity of the crops due to poor soil quality, low nutrient use efficiency, inappropriate water management strategies [5] and lack of arable land and freshwater [6].

Figure 2.

Steps involved in the crop production system (first step).

2.1.1 Seedbed preparation

The seedbed preparation is cumbersome and consumes about 30% of the total energy in the production system. It involves subsoiling, primary and secondary tillage machinery. Subsoiling is the process of breaking the hard pan or plough sole formed after years of cultivation or movement of livestock or transportation machinery. The stress is usually transmitted by means of soil particles and converges at a single point. As the process continues, a layer of hard soil is formed that prevents the penetration of the roots and accumulates the water in the root zone, Figure 3. This process is known as soil compaction. It is recommended to use subsoiler after every 4–5 years to break the hard layer or plough sole. The subsoiler is a single-standard plough that penetrates deep within 45–100 cm or more and breaks the hard pan. It is operated by the >50 hp. tractor. However, when the hard pan or plough sole is formed within 20–25 cm depth, a chisel plough with many standards can be used. The subsoiling operation is followed primary tillage. The primary tillage is carried out with mould board plough and disc plough to reach to a depth of 20 cm. The movement of the tillage tool generates a triangular wedge that moves forward and causes breakdown of soil layers. The clods raised from the primary tillage undergo size reduction in secondary tillage operation in the range of 8–12 cm by cultivator, rotavator and disc harrow.

Figure 3.

Generation of stress concentrating points in the plough sole.

2.1.2 Sowing/transplanting

The process of placing the seeds or seedlings in the well-prepared seedbed is termed as sowing or transplanting. The metering system of the seeder contains a horizontal or vertical disc with grooves on the outer periphery to drop single seed at one time [7]. In case of transplanting operation, like in paddy or vegetables, a special type of mat seedling is used and finger-type transplanter picks one seedling at a time and plants it in the soil. A number of manual, power-operated and self-propelled seeders and transplanters are available for sowing or transplanting of seeds or seedlings at different rates and planting distances.

2.1.3 Irrigation

The seeds in the seedbed require sufficient moisture to sustain the metabolic activities and provide feasible conditions for the emergence of the plants. Traditionally, the irrigation is provided by flooding method; however, it results in wastage of water and possesses less efficiency. The modern system involves sprinkler and drip irrigation with sophisticated systems to ensure high water use efficiency and less wastage. The governmental agencies are also thrusting to involve sprinkler and drip irrigation system to ensure ‘more crop per drop’. Recently, Internet of Things (IOT)-powered in situ real-time monitoring system has enabled to improve water use efficiency [8].

2.1.4 Weeding

The growth of the plants also results in the growth of unwanted weeds. These weeds interfere with the growing mechanism of the plants and create a competitive environment for the assimilation of nutrients, water and fertilizers. The weeds are removed by chemical methods and mechanical weeders. The mechanical weeders are manual, power-operated, self-propelled and battery operated, Figure 4.

Figure 4.

Farm machines for horizontal cultivation system.

2.1.5 Harvesting

Harvesting is the process of reaping (cereal crops), plucking (fruit crops), digging (root crops) by manual or power-operated mechanical harvesters [9]. A power-operated mechanical harvester or combine comprised of a collection unit, threshing cylinders, cleaning mechanism, collecting system and chaff blowing unit. The crop dividers and reel intend to divert the standing crop towards the reciprocating cutter bar. The harvested crop is fed to the threshing cylinders through a conveying mechanism. The threshed grain passes through the reciprocating screen to separate the grains from the chaff. The clean grain is collected in the trays placed at the lower side. The chaff is blown and collected separately. The losses in combine are limited ranging from 2.5% in pulses and cereals and 4% for soybean.

2.1.6 Threshing

The harvesting operation is followed by threshing, which results in the segregation of plants and grains/fruits. However, these days, combine is often used as it can harvest, thresh, clean and collect in single operation. There are five types of threshers depending on the type of crop and usage: wire loop, spike tooth, syndicator type, hammer mill type and rasp bar type.

2.1.7 Post-harvest operations

The post-harvest operations intend to reduce the losses and enhance the shelf life of the agricultural produce.

2.1.8 Storage

The storage of the agricultural produce is the last step in the chronological process of production system to preserve and protect the crop for future use.

2.2 Vertical cultivation system

Vertical pattern of cultivation is perceived as the panacea of the ills of horizontal pattern of cultivation. The problems of small size, high labour requirement and demand for urban land have compelled to shift towards vertical farming system [10]. In this method, the space is utilized judiciously by creating stepwise layer system of cultivation. The vertical cultivation system is a vertically stacked layered system, where the grain crops, vegetables and fruit crops are grown in artificial or mechanically controlled conditions in cities and urban areas [11]. These vertical farms use a combination of solar panels to control the lighting system, temperature monitoring system, sensors, air humidity and maintenance unit to reduce the impact of environmental parameters and lower down the cost of production, Figure 5. It also uses soilless techniques to grow the plants by supplying the nutrient solution through the root zone of the plants [12]. The vertical cropping system results in an increase in the productivity of the crop per unit base area. According to Touliatos et al. [13], the production of lettuce was significantly (13.8 times) higher in vertical farming in comparison with horizontal cultivation system.

Figure 5.

Automated farm production system.

The benefits of the vertical farming system outnumber the benefits of horizontal farming system, Table 1. However, the main challenge is to reduce the cost and energy consumption, which is directly or indirectly responsible for increasing the carbon footprint. The cost can be splitted into capital cost used for fabrication of farm and operational cost for running the farm on daily basis. When the farm is small, major costs are incurred on capital costs; when the farm is large, it is tilted towards operating costs viz. heating, ventilation and air conditioning (HVAC). Banerjee and Adenaeuer [16] modelled and concluded that the vegetable production in vertical farm requires 14 GWh of power per hectare per annum, which is much higher than 1.75 GWh per hectare per annum in horizontal farming [17]. Moreover, the initial fabrication installation cost of vertical farming system is higher than conventional agricultural setup.

Type of system	Benefits	Reference
Vertical farming	Higher productivity	[13]
	Different crops in different layers	[6]
	Protection from vagaries of climate and natural disasters	[6]
	Multiple harvest round the year	[14]
	Reduction in the usage of fossil fuels	[6]
	Protection of environment from methane emissions	[15]

Table 1.

Benefits of vertical farming system.

3. Urban agriculture

Urban agriculture is often discussed owing to rising poverty, food shortages and nutritional deficiency in the urban cities. It can be inferred as mixed system of vegetables, fruits, trees and condiments with main thrust on reducing the expenditure and augmenting the income. The urban agricultural system has the proclivity to supply 8% proteins and 40% calcium intake to poor city dwellers [18]. It is a viable approach towards reducing the vulnerability, survivability and food security of the urban poor. Urban agriculture offers multiple benefits (Figure 6), particularly in terms of sustainability, accessibility to green spaces, recreation activities, health benefits, inclination towards nature, reduction in transportation cost, mitigation of adverse climatic events, promotion of resource use efficiency and income augmentation [19]. However, the city lands are often used for activities that produce the highest net income [20]. Accordingly, the preference for the allocation of the land is mostly non-agricultural activities. The diversion has the inclination to jeopardize food security and augment poverty levels [21]. The discrimination has pushed the agriculture towards the outer periphery of the urban areas, a term called peri-urban agriculture [22].

Figure 6.

Services offered by the urban agriculture.

Peri-urban agriculture, implying agricultural setup in the midst of cities and rural areas, is characterized by poor infrastructure, less human population density and availability of large areas for agricultural activities [23]. However, the main thrust of peri-urban agriculture is income generation as the associated farmers are mainly professionals [24]. The urban agriculture is categorized into three categories depending on the type of technology used for the cultivation of crops, Figure 7.

Figure 7.

Technologies used in urban agriculture.

The proper composition of physiological and environmental parameters is indispensable for the growth and development of plants. These parameters include temperature, light, relative humidity and nutrient availability; presence of moisture dictates the quality of the plant and productivity of the crop. These parameters are controlled in hi-tech greenhouses and plant factories [25].

3.1 Hydroponics

The traditional horizontal agricultural system requires soil to grow the crops. In hydroponics, the crops are grown in natural or artificial substrates (soil free environment) and the nutrients (micro and macro) are supplied to the root zone of the plants [26]. The substrates can be organic, inorganic or synthetic [27] with different properties, Table 2. The commonly used fertilizers in hydroponic system include ammonium nitrate (NH₄NO₃), phosphoric acid (H₃PO₄), calcium nitrate {(CaNO₃)₂} and nitric acid (HNO₃). The chemical formulations are sold in three-digit sequence of nitrogen (N), phosphorus (P) and potassium (K) viz. 8–15–32 implying 8% N, 15% P and 32% K. It is also important to replenish the water in the nutrient solution continuously to keep the nutrients appropriate to the growth of the plants. In fact, the nutrient solution in the tank should be changed, and tank should be cleaned and disinfected after every 2 to 3 weeks [30]. The system also uses sensors, software, microcontrollers, mobile applications, web platforms and computing devices to control the climatic parameters, lighting and irrigation scheduling. The expansion of the hydroponic system is farfetched and the market is expected to grow at 20.7% CAGR from 2021 to 2028 [31]. Hydroponics is termed as the best alternative for urban and peri-urban agriculture and a futuristic approach to achieve ‘sustainable cities and communities’ goal of United Nations’ Agenda for Sustainable Development 2030.

Substrate		Properties	Reference
Organic	Peat Coconut fibre Sand Pumice Vermiculite	pH	—
		Electrical conductivity	—
		Bulk density	[28]
		Porosity	[28]
Inorganic	Stonewool Zeolites Expanded clay Perlite	Water holding capacity	[29]
		Cation exchange capacity	[28]
Synthetic	Polystyrene Polyurethane foam
		Cost	-

Table 2.

Substrates used in hydroponics.

The basic structure of the hydroponic system comprises of a perforated tray, reservoir, pump, delivery tubes, aerator/air pump and lighting system. The selection of the hydroponic systems depends on environmental conditions, cost, type of the crop, level of technology and acceptability, Figure 8. Hydroponic system results in higher yield and lower water consumption in lettuce [32] and higher plant survival in strawberries [26]. However, the energy consumption is much higher [32] and waste water treatment is minimal.

Figure 8.

Types of hydroponic system.

3.1.1 Deep water culture

The storage tank with nutrient solution contains spaces to place the plants and an aerator to circulate the oxygen continuously. The roots of the plants are immersed in the nutrient solution, while the upper half remains outside the tank with the help of wood, polystyrene or cork bark.

3.1.2 Drip system

It is similar to deep water culture; however, the nutrient solution is pumped through a common channel that contains the roots of the plants. The solution is supplied at specific time intervals in controlled flow and the residual solution is bypassed to the storage tank/reservoir. This method is suitable for specific crops viz. tomato and pepper.

3.1.3 Nutrient film technique

This technique relies on supplying the nutrient solution to the roots of the plant continuously. A number of trays can be placed one above the other to reduce the space constraints and increase the productivity of crops.

3.1.4 Ebb and low

It is a system in which the plants are kept in a tray filled with nutrient solution. The nutrient solution is pumped from the tank placed below the tray. The recycling of water is ensured by the force of gravity.

3.2 Aquaponics

The aquaponics establishes symbiotic relationship between fish and plant growth. The sludge of the fish, rich in nutrients, is used as the nutrient medium to support the growth of the plants. This forms a sustainable ecosystem in which the plants grow on one side and microbial process of nitrification/denitrification on the other side.

3.3 Aeroponics

‘Aero’ means air i.e. the nutrient solution is absorbed by the plant roots in air. In this method, the nutrient solution is sprayed by means of sprinklers in a common zone and the roots absorb the nutrients from the air. It is advantageous as the roots get aerated from the oxygen present in the sprayed solution.

However, there are certain challenges that must be rectified to ensure the sustainability and viability of hydroponic system. The initial cost of fabrication, installation and equipment is high. The operator must be skilled with sufficient knowledge of agriculture, electronics, plant physiology and plant pathology. Moreover, the residual nutrient solution must be properly disposed as it may pollute the ecosystem.

3.4 Automation in vertical cultivation

Modern technological techniques such as artificial intelligence and machine learning-based neural network, deep learning, fuzzy logic, big data and Bayesian network are employed to improve the working performance of the hydroponic system [33]. Internet of Things (IOT) is believed to have a number of applications in vertical cultivation system. It integrates different sensors with microcontrollers and Wi-Fi modules to manage the resources in real time [8]. It helps in reducing the manual errors and improves the productivity of the crops. The biosensors can provide real-time data that help in detection of diseases and pests [34] and make logical decisions [35].

4. Protected cultivation system

The greenhouses are used for raising of crops, mainly to protect them from harsh climatic conditions and extension of the cultivation season, Figure 9. It integrates different renewable sources to promote and sustain crop growth [36]. Solar energy for electricity [36] and drip irrigation for water conservation [37, 38] improves the economic viability of the greenhouse cultivation system [39]. In fact, greenhouse irrigation sensor-based automation system is perceived as the effective method to prevent the wastage of water [40].

Figure 9.

Automated greenhouse structure.

It also provides a window of opportunity to cultivate off-season crops. The greenhouses are usually made from plastic, glass or polyethylene to allow the radiations to pass through and contribute towards plant growth. The greenhouse can be open, semi-closed and closed type. In open type, there is no provision to collect and reuse the drained water. The semi-closed type has small windows with low cooling capacity and mechanical ventilation system. The semi-closed type reuses the drained nutrient solution by collecting it in a reservoir that is topped-up with fresh water on regular basis. In closed type, the water follows a closed loop for collection, distribution, recycling and re-distribution. The mechanical system is used for cooling and dehumidification by air treatment accessories.

The polyhouse’s are categorized (Figure 10) on the basis of shape, utility, construction and covering material [41]. The cost of the construction is an essential parameter of the poly house. Accordingly, it is categorized into low-cost green house, medium-cost green house and high-cost green house.

Figure 10.

Types of greenhouses.

5. Waste management

Urban agriculture relies on utilizing plant residues and kitchen waste for production of bio-fertilizer [42]. The wastes can be converted into compost or vermicompost for round-the-year agricultural production activities. However, the space is the limiting factor in the urban areas [43]. The involvement of low-cost smart vermicomposting bin with automatic watering and mixing system can help to transform the wastes into fortified vermicompost [44]. A single large space can also be devoted towards the preparation of compost through windrow composting [45]. In windrow composting, the degradable materials are laid in the form of long windrows, microbial culture is added to increase degradation rate and mixed at regular intervals (Figure 11) with the help of windrow turner [45].

Figure 11.

A tractor-operated windrow turner in working mode [45].

6. Conclusion

The shrinkage of the land and increased wages has compelled to shift towards mechanization in both horizontal and vertical cultivation systems. The mechanical systems are undergoing a transformation towards automation to reduce the manual errors and improve their efficiencies. On the other hand, the vertical mechanical systems and automations might witness a reduction in the installation, operational and maintenance cost for higher adoptability among the stakeholders. The success of the mechanical farming systems might be directly linked with the security, sustainability and environmental viability of the world in near future.

Acknowledgments

The support and help rendered by the officials at SKUAST-K and IARI is highly appreciated and duly acknowledged.

Conflict of interest

The manuscript was prepared unanimously. Hence, no conflict of interest exists.