Types of Cultivation in Greenhouses

Types of Cultivation in Greenhouses: History

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Subjects: Agriculture, Dairy & Animal Science

Contributor:

Julio C. Sosa-Savedra

Greenhouse cultivation includes two types: conventional and hydroponic (cultivation substrate in soil, and cultivation substrate in water-based nutrient solution, respectively). Greenhouse cultivation systems have garnered substantial attention due to their ability to create a controlled environment for crop growth, resulting in higher yields, improved quality, and reduced water usage.

life cycle assessment
energy consumption
greenhouse structure

1. Introduction

Today, the surging global population and the escalating demand for food have drawn significant attention from scientists and researchers towards the agricultural industry and energy consumption [1,2,3]. One of the key challenges in this field revolves around addressing the needs of a rapidly expanding global population and their growing demand for food [1,4,5]. Therefore, the goal to enhance food production through the development of new technologies should be a primary focus for researchers [1,6,7]. Improving energy consumption and associated costs in sustainable agriculture is crucial for preserving the environment, conserving natural resources, and maximizing economic benefits. This requires finding a balance between ensuring food security and minimizing environmental impact [2,8]. The greenhouse sector has become a growing interest within the agricultural industry, steadily progressing with each passing day [5,9]. One of the key benefits of this type of cultivation is its ability to produce crops outside the traditional growing season. This extended period of cultivation requires additional energy compared to traditional agricultural practices on farmlands. Traditional agriculture requires a large area under cultivation, natural minerals, and water, which reduces productivity. Also, weed removal requires a lot of effort and energy consumption that can reduce productivity (Table 1). Table 1 shows a brief comparison of two methods of farming in the open field and cultivation in the greenhouse.

Table 1. Comparison between traditional and hydroponic cultivation.

Open field cultivation	Greenhouse Cultivation
Large cultivation area is needed	Optimal use of water
The need for natural minerals	Off-season cultivation
Hard weed removal	Higher yield and nutrient content
Water wastage	Control of environmental conditions

Greenhouse cultivation includes two types: conventional and hydroponic (cultivation substrate in soil, and cultivation substrate in water-based nutrient solution, respectively). Conventional greenhouses can grow the plant in a soil bed with a controllable environment [10]; in fact, the vital environmental factors for plant growth can be kept at an optimal level to create a favorable climate inside the greenhouse [1,11,12]. Greenhouse cultivation is becoming more and more popular and today there are about 405,000 ha of greenhouses around the world [1,13]. Conventional greenhouse cultivation (cultivation substrate soil) has some disadvantages, including the need for a large area under cultivation that requires high concentrations of nutrients and pesticides [1,14,15]. In addition, chemical wastes and pollutants released during cultivation can have dangerous effects such as soil degradation, erosion, and pollution [1,16].

Hydroponic cultivation is a kind of cultivation where the plant is placed in a bed using air, water, or solids containing moisture instead of soil [17]. This cultivation provides better quality, has a higher yield, and nutrient content, and better consumption of fertilizer and water compared to conventional greenhouse [1]. Also, hydroponic cultivation is one of the most popular techniques. This method is clean and easy compared to the conventional manner [17,18]. Traditional agriculture requires a large area under cultivation, natural minerals, and water, which reduces productivity. Also, weed removal requires a lot of effort and energy consumption that can reduce productivity. Hydroponics can control the temperature, humidity, and irrigation level by a control system consisting of a microcontroller kit connected to a wireless sensor network (WSN) [17,19]. Hydroponics is a special and useful method for growing plants that can be used even in dry areas such as arid deserts [17,20]. Based on some comparisons between hydroponic and open-field cultivation, crop yield per unit area has been about 10 times higher than conventional cultivation on open land [21,22]. In arid or semi-arid areas, it is common to use low-quality water (high salt concentration) for agriculture because this is the only source available [23,24]. These waters contain a large amount of salt and sodium ions, which cause physical and chemical changes in soil structure and helps to destroy it [21,22]. As a result, it has a negative effect on the number of plant leaves, leaf surface, relative water content, and biomass, and it also reduces productivity [23,24]. Thus, hydroponic cultivation can become a significant strategy because the matric potential in this type of cultivation will not exist under the free energy of water and only includes the osmotic potential [23]. However, in conventional greenhouse cultivation, where the soil is the substrate for plant growth, both matric and osmotic potentials cause less water to be available for the plant [21,25].

In general, water salinity in the hydroponic method is less harmful than in conventional cultivation because of the constant amount of oxygenation (O₂) [26]. Therefore, agricultural production in greenhouse systems has both advantages and disadvantages. Its advantages include producing more than one type of product in a year, producing regardless of weather conditions, identifying the essential needs of plants and environmental effects, increasing production per unit area, implementing a marketing plan, and identifying target market demands; its disadvantages are the excessive use of local non-commercial energy sources [27] such as the energy of seed, livestock manure, and commercial energy sources such as machinery, irrigation water, diesel power, pesticides, fertilizers, and so on. Furthermore, inputs used in greenhouse structures, such as steel, polyethylene, and polycarbonate sheets, as well as the shape of the greenhouse buildings, can increase greenhouse gas (GHG) emissions and energy utilization compared to cultivation on agricultural land.

2. Conventional Cultivation

Greenhouse cultivation is a method that controls the indoor cultivation environment and optimizes it for crop growth and development [52,53]. The controlled environment of the greenhouse provides the possibility of producing crops in diverse climates and seasons [10,54] (Figure 1).

Figure 1. Conventional greenhouse system [54,55].

Controlling the cultivation environment increases the yield of the product and reduces the consumption of water and chemical pesticides [35]. In addition, this type of cultivation faces very difficult challenges, including a reduction in the soil fertility and crop productivity due to continuous cultivation [56,57,58,59]. The environmental situation required for the growth of plants includes regulating the temperature, moisture, and accessibility of light and water [10]. As a result, greenhouses are more energy-intensive than other sectors of agriculture [27,35]. Some agricultural products such as fruits, vegetables, and flowers are cultivated in greenhouses. Energy supply in the greenhouse is generally the second major expenditure of production after the labor cost, which accounts for 25% of the operational cost of large vertical fields in the United States [60]. Reducing energy demand to increase crop yield in greenhouse cultivation is recognized as a sustainable industry production goal [61]. Fuel and electricity are used to control the internal environment of the greenhouse, with the aim of performance and stabilizing quality improvement, but increasing the price of these resources has reduced the profits of farmers [52,62,63]. Excessive use of non-renewable energy sources such as diesel fuel causes negative environmental effects, including GHG emissions and energy consumption. The substitution of fossil fuels with renewable energy sources (RESs) plays an essential role in incrementing the quality of the living environment and reducing the emission of GHGs [64,65]. Therefore, increasing high-quality production to optimize energy and enhance the farmers’ profits is a challenge for researchers. Hesampour et al. [9] investigated the cucumber fruit cultivation stages in a greenhouse from energy, economic, and environmental aspects of greenhouse cucumber production. Table 2 presents the energy equivalent of all the inputs in that study.

The essential information in this table is obtained through the questionnaire, databases Simapro version 7.2 (a sustainability software for analyzing sustainability performance through life cycle assessment (LCA), used globally by industry and academia) and Ecoinvent (a top LCI database with 17,000+ unique datasets covering various products, services, and processes), and previous studies. The data relating to the machinery can include the practical lifetime of the machine, the number of activity hours over the efficient lifetime and the growing season, as well as the weight of the machinery. The use of nitrogen fertilizer has harmful consequences, including global warming and the potential for acidification in the environment [66,67].

Table 2. Energy equivalent of all the inputs for greenhouse cucumber production.

Items	Energy Equivalent (MJ unit⁻¹)	References
Human labor (h)	1.96	[68,69,70]
Diesel fuel (L)	56.31	[71]
Electricity (kwh)	11.93	[67,72]
Transportation (tone.km)	3.05	[73]
Chemical pesticides (kg)	101.2	[74]
Chemical fertilizer (kg)	-
Nitrogen	78.1	[75]
Phosphate	17.4	[75]
Potassium	13.7	[76]
Micronutrients (kg)	120	[77]
Manure (kg)	0.3	[78]
Water (m³)	1.02	[75]
Natural gas (m³)	49.5	[79]
Machinery (kg)	62.7
Nylon (kg)	17.91	[80]
Steel (kg)	27.73	[81]
Plastic general (kg)	90
Cucumber (kg)	0.8	[82]

The usage of structural materials and phosphorus fertilizer in the potential of eutrophication is effective in reducing energy consumption in the greenhouse [9,83,84]. Extensive studies have been conducted in the field of energy consumption and the factors affecting it in conventional greenhouse cultivation. Table 3 shows some of these studies.

Table 3. Various studies conducted on energy consumption in conventional greenhouses.

Refs.	Titles	Purpose and Review	Results
[35]	Energy-efficient operation and modeling for greenhouses: A literature review	Existing strategies in energy efficiency control operations; Advanced simulations of greenhouse energy	The result showed that the cost and precision of sensors restrict the adoption of optimal controls by growers.
[85]	Manufacturing energy and greenhouse gas emissions associated with plastics consumption	Comparison of energy supply chain requirements; Greenhouse gas emissions caused by plastic production technologies; Development of bioplastic production technologies	The results indicated that commodity polymers, with a global consumption of 1 MMT per year, cause 3.2 quadrillion Btutus of energy and 104 MMT CO_2e of GHG emissions annually in the US alone.
[86]	Demand side management of energy consumption in a photovoltaic integrated greenhouse	Analysis of activities in greenhouse production and electrical equipment performance; Particle swarm optimization scheme; Analysis of the energy consumption program in the greenhouse	The results showed that the optimization plan is useful for directing production activities in greenhouses and building photovoltaic integrated greenhouse systems.
[87]	Modeling and experimental validation of heat transfer and energy consumption in an innovative greenhouse structure	Modeling and experimental evaluation of heat and mass transfer functions in a solar greenhouse with a thermal screen	The results revealed that implementing a thermal screen could decrease both the final cost and air pollution.
[88]	The potential contribution of food wastage reductions driven by information technology on reductions of energy consumption and greenhouse gas emissions in Japan	Analysis of the effects of food waste; Reducing energy consumption; Reducing greenhouse gas emissions	The results showed that the reduction of GHG emissions would be between 5.6 to 7.8 million tons of CO_2-eq per year.
[89]	Methodologies of control strategies for improving energy efficiency in agricultural greenhouses	Systematic review of control strategies to improve energy efficiency in greenhouses (especially low-energy greenhouses)	The results showed that 60% of the selected articles on greenhouse climate management consider temperature and humidity as controlled parameters.
[9]	Energy-economic-environmental cycle evaluation comparing two polyethylene and polycarbonate plastic greenhouses in cucumber production (from production to packaging and distribution)	Investigation of energy flow, economic benefit, and environmental effects in cucumber greenhouse cultivation; Measurement with two methods of LCA and Cumulative Exergy Demand (CExD) considering different greenhouse structures	The LCA results showed that the main environmental impacts come from direct emissions due to input consumption (air: carbon dioxide (CO₂), and nitrogen oxides (NOx); soil: mercury (Hg), copper (Cu), and lead (Pb)) and indirect emissions induced by the production of chemical fertilizers, greenhouse structures, and chemical pesticides.
[90]	Impact of environmental factors on the energy balance of greenhouse for strawberry cultivation	Effects of solar greenhouses on strawberry cultivation in temperate regions; Energy required to heat the greenhouse; Experimental investigation of ambient temperature, solar radiation, and relative humidity	The result showed that passive solar heating may not suffice in cold regions with extended cloudy weather, requiring additional gas or electricity-based heating systems.
[91]	Thermo-environomic assessment of an integrated greenhouse with an adjustable solar photovoltaic blind system	Energy plus modeling as a greenhouse reference in rose cultivation; Validation of the developed greenhouse model with experimental site measurements; Investigating ambient temperature in the greenhouse with a photovoltaic system	The results showed that covering 19.2% of the roof can reduce natural gas consumption, electricity demand, and CO₂ emission by 3.57%, 45.5%, and 30.56 kgm⁻² annually, without affecting plant canopy illumination levels.
[92]	Nanomaterials application in greenhouse structures, crop processing machinery, packaging materials, and agro-biomass conversion	Application of nanomaterials in agricultural products; Investigating nanotechnology in climate control and photosynthesis of plants in the greenhouse	The reviewed work indicated that nanotechnology has the potential to enhance agricultural production.
[52]	Energy-sustainable greenhouse crop cultivation using photovoltaic technologies	Examining the important aspects of greenhouse cultivation and the electricity required; Studying state-of-the-art photovoltaic systems in the greenhouse and their shading effects on plants; A vision for sustainable greenhouses with photovoltaic technologies	The results showed that solar cells can be used in greenhouses to generate electricity, but the shading from photovoltaic panels can impact plants below.

3. Hydroponic Cultivation

Hydroponic or liquid culture is one of the specialized methods for growing plants, which provides conditions for plant growth without soil (Figure 2) [56,93].

Figure 2. Hydroponic greenhouse system [93].

Hydroponics is a type of culturing method in which a nutrient solution is used instead of soil and can save the consumption of essential resources for crop growth [94]. This method will create the highest efficiency in a large space by delivering water to the thirsty roots of plants based on their needs, with the least amount of human energy and water resources [95]. The diet in hydroponic production is very optimal and based on the needs of the plant, which allows these products to have a better and healthier quality than their counterparts in soil cultivation. Because of the precise regulation of watering and feeding the plant, this method is superior to the traditional method [96,97,98]. Hydroponic cultivation is expanding dramatically to increase crop productivity, especially in developed countries such as China and the United States. Some agricultural products such as cucumber, lettuce, and tomato have been studied in this cultivation [99,100,101]. Researchers have concluded that hydroponic cultivation has various results on different crops and many types of research have been performed on energy consumption in this type of cultivation (Table 4) [56,102].

Table 4. Research conducted on energy consumption in hydroponic greenhouse cultivation.

Refs.	Titles	Purpose and Review	Results
[2]	Recycling drainage effluents using reverse osmosis powered by photovoltaic solar energy in hydroponic tomato production: Environmental footprint analysis	Measuring the environmental benefits and trade-offs of reverse osmosis integration; Recycling of greenhouse drainage effluents using photovoltaic solar system; Comparison of the environmental footprint of tomato production in two types of conventional and hydroponic cultivation; Comparison of three independent sources of irrigation	The results showed that using brackish groundwater as a substitute for desalinated seawater can reduce the global warming footprint by 27%.
[17]	Hydroponic and Aquaponic Farming: Comparative Study Based on Internet of things IoT technologies	Comparison of hydroponic and aquaponic cultivation systems; Using the automatic technology of the Internet of Things (IoT)	The results showed that implementing a depth-camera module in the system offered an advantage, and a mobile application to maintain the ecological balance of the environment.
[103]	Validation of a building energy model of a hydroponic container farm and its application in urban design	Validation of Energy Plus model in container hydroponic culture; Continuation of experiments for nine months and data collection; Studying energy consumption and its optimization	The results showed that stakeholders can reliably predict annual container farm energy use by representing plant–air interactions within EnergyPlus.
[1]	Autonomous greenhouse microclimate through hydroponic design and refurbished thermal energy by phase change material	Evaluation of the microclimate of hydroponic greenhouse cultivation without heating; Hydroponic design evaluation; Comparison of environmental conditions inside the greenhouse during the day and night	The results showed that hydroponic greenhouses offer better conditions than conventional ones, with temperatures above 18 °C and a humidity range of 20–35% during the day.
[104]	Hydroponic system and desalinated seawater as an alternative farm-productive	Comparison of energy consumption of lettuce production in two types of conventional and hydroponic greenhouse cultivation; Investigating the amount and emission of greenhouse gases; Comparison of different percentages of desalinated seawater for irrigation	The results showed that desalinated seawater with hydroponic systems can sustain agriculture but relies heavily on energy.
[21]	Comparison of soil and hydroponic cultivation systems for spinach irrigated with brackish water	Measurement of differences in the water status of spinach plants; Using brackish water to grow plants in covered soil, non-covered soil, and hydroponic cultivation system; Investigating the leaf water and osmosis potential of the product and also its regulation	The results showed that the spinach plant adjusts to salinity with adaptive strategies by increasing osmotic adjustment and leaf succulence, reducing leaf water potential. Sodium concentration in leaves and fresh weight are highest in hydroponic cultivation, especially with brackish water.
[56]	Evaluation of hydroponic systems for the cultivation of Lettuce (Lactuca sativa L., var. Longifolia) and comparison with protected soil-based cultivation	Investigating the suitability of hydroponic cultivation of lettuce in replacing greenhouse soil-based cultivation; Study of two hydroponic techniques including deep-water culture and nutrient film technique and compare them with conventional greenhouse cultivation; Using Tukey’s test to investigate crop performance, water consumption and economy	The results indicated that hydroponic techniques outperformed soil-based systems with a higher yield, simplicity, ease of operation, economic feasibility, and nutritionally superior produce.
[33]	A new method for green forage production: Energy use efficiency and Environmental sustainability	Evaluating energy and water consumption in hydroponic fodder production; Study of environmental indicators	The results showed that despite the many benefits of hydroponic fodder on livestock nutrition, its greenhouse cultivation imposes many adverse environmental effects.

In this method, the plant’s growing season is an effective parameter for the level of economic productivity of this type of cultivation. So, food production techniques are advancing, and hydroponic cultivation has proven that it does not have many of the problems associated with conventional greenhouse cultivation [1]. In a study about green fodder production by hydroponic method, energy consumption performance and environmental sustainability were investigated [33]. Physical input data used in greenhouses and the energy of each were obtained using a questionnaire from 18 greenhouses with green fodder production using the hydroponic method, as shown in Table 5.

Table 5. Input and output data of energy consumption in hydroponic cultivation method.

Items (unit)	Energy Equivalent (MJ unit⁻¹)	References
Human labor (hr)	1.96	[70]
Stationary equipment (kg yr)	9	[80]
Natural gas (m³)	49.5	[80]
Nitrogen fertilizer (kg)	66.14	[105]
Pesticides (kg)	199	[106]
Electricity (kWh)	11.93	[107]
Seed (kg)	14.7	[108]
Hydroponic Fodder Yield (kg)	1.66	[109]

The whole electricity consumption for greenhouse facilities, lighting, etc., was registered by phase meter. Natural gas is used to heat the indoor environment of the greenhouse and its amount can be calculated with a gas meter. To calculate fodder energy by the hydroponic culture method, in the first step, the amount of dry matter during the growth period was determined. Then, with the energy metabolism of fodder dry matter, the energy equal to hydroponic fodder was calculated [33]. The energy indices of Energy Ratio (ER), Energy Productivity (EP), and Net Energy (NE) were calculated by calculating the amount of input and output energy as follows [70,110]:

E R = \frac{O E}{I E}

E P = \frac{H F Y}{I E}

N E = O E - I E

where ER is the energy ratio; OE and IE are output and input energies; EP is energy productivity; HFY is Hydroponic Fodder Yield and NE is Net Energy.

Various environmental factors are effective in greenhouse cultivation, both conventional and hydroponic, which are explained below. In this regard, Figure 3 shows some environmental factors that can be investigated in greenhouse cultivation.

Figure 3. Some effective environmental factors in greenhouse cultivation [81].

This entry is adapted from the peer-reviewed paper 10.3390/su16031273

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