1. Introduction
In Turkey, the first greenhouse activities began in the 1940s [
1], and greenhouse cultivation increased significantly after the 1980s in terms of cultivated areas. The seedling sector, which has the most important input share in greenhouse production, started its activities in Antalya province in the 1980s and increased its commercial activities with modern greenhouses in the 1990s [
2].
Tomato is the most produced seedling variety both in Turkey and the Antalya province. According to the official data of 2017, total vegetable seedling production is approximately 2.9 billion plants and tomato seedling has the highest share with 36.9%. The total amount of grafted seedling produced in 2017 was 54 million plants and 92.3% of this quantity was produced in the Antalya province [
3]. Seedlings, especially grafted seedlings, have strategic and economic importance because they affect the yield of other agricultural products and final product quality.
Being a diverse field, the agriculture sector supplies many vitally important products to society. The pressure on agricultural production as food, use of energy, and various high-value by-products will increase due to the competition for limited natural resources while the world population grows [
4]. As a result of the ongoing increase in the human population, agricultural production, and the frequent usage of intensive technology, the impact assessment of these processes has become an important issue to be examined.
Impact assessments are divided into subgroups, which are mainly environmental impact assessments, strategic environmental assessments, social impact assessments, health impact assessments, risk impact assessments, and life-cycle assessments (LCA) [
5]. According to the bibliometric study made by [
5], who analyzed articles published within the journal “Environmental Impact Assessment Review” between 1980 and 2018, the keyword co-occurrences score of LCA is high when compared to other environmental assessments.
The LCA concept was first developed in Europe and the USA in the late 1960s to conduct wide-ranging environmental impact assessments in the early 1970s [
6]. Today, LCA is a popular approach for identification, quantification, and environmental impact evaluation of production processes from cradle-to-grave and for finding solutions to minimize the environmental damages caused by these impacts [
7]. As a production process and having a high economic role in agriculture, vegetable seedling production poses a potential risk due to the high consumption of resources that cannot be easily replenished like peat, coal, and water [
8].
While normal agricultural inputs such as pesticides, fertilizers, water, peat, and coal are used in the production of grafted seedlings, support materials such as expanded polystyrene (EPS), plastics, and silicone are used extensively too. This is because the production of a grafted seedling requires a separate production technique with more input and processing than a normal seedling. The aim of the grafting technique is to briefly increase the strength and yield of a plant by grafting it on another seedling. Thus, after grafting, the grafted seedling will have superior properties to a normal seedling.
Although there are environmental studies on vegetable seedlings in the literature, those relevant to grafted tomato seedling production are rare. The number of studies having a title that contains both “LCA” and “Seedling” terms is 4 in Google Scholar [
9] while it is 3 in Science Direct [
10]. Furthermore, we could not find any LCA study about grafted tomato seedlings.
The main objective of this study is to make an environmental impact analysis of a single grafted tomato seedling produced in Turkey by using LCA methodology. It aims to determine the inputs related to the grafted tomato seedling production during the cycle, starting from pre-production to the post-harvest process, and to analyze the environmental impacts of the input materials, processes, and methods used. Thus, by making this analysis, the inputs having the highest environmental impact can be detected and alternate input or method suggestions can be given. Additionally, it is desired that we contribute to the literature by using the LCA approach. This study can also be considered as an agricultural reference on grafted seedling production since it also covers the contents not directly related to LCA.
2. Materials and Methods
2.1. The Importance of the Study Region Antalya for Seedling Production in Turkey
Antalya province ranks first in seedling production in Turkey [
3]. Besides, the center of the “Fidebirlik” (Sub-Union of Seedling Producers), which, legally, all seedling producers have to be a member of, is located in Antalya.
Table A1 shows the distribution of nurseries based on location [
3]; thus, we can also see the predominance of Antalya for the relevant study and objectives.
2.2. The Differences Between Grafted Seedlings and Normal Seedlings
Grafted seedlings have many advantages when compared to normal seedlings. These are resistance to soil-borne diseases, salinity, excessive moisture, drought, low soil and air temperature tolerance or endurance, effective use of water and plant nutrients in the soil due to its strong root structure, strong plant structure, and, accordingly, a long harvest period. On the other hand, the disadvantages are extra time, place, and production material needs for grafting, being well equipped with experienced staff requirements during and after grafting, occasional dispute problems, increased production costs with hybrid rootstock use, and product quality variability depending on rootstock selection [
11]. When we consider these advantages and disadvantages, it is obvious that the parameters of an LCA study on grafted seedlings will be different when compared to normal seedlings.
2.3. Production Stages of Grafted Seedlings
Because grafted seedling production differs from normal seedling production, the production stages also differ from normal seedlings, as seen in
Figure 1. We also need to say that fertilization, irrigation, and pesticide application are involved in all stages of seedling production.
2.4. Materials of the Study
The main material of the study is composed of primary and secondary data. As a secondary data source, the indicators related to nurseries in Antalya province were obtained from Fidebirlik and relevant scientific researches. The total production area of the nurseries, which are close to Antalya city center, is 318,000 m
2 [
3]. The study was conducted in 49% of this area and the selected nurseries used similar production inputs and methods. The primary data source is based on the data obtained from the survey done by face-to-face interviews with the authorities in the nurseries. Within the scope of the study, accounting, administration, production, and marketing departments of the establishments were contacted separately. The first part of the survey consists of questions about the general characteristics of the nurseries; the second part consists of questions about production inputs, processes, and methods.
2.5. System Boundary and the Definition Criteria
The system boundary (dotted background) of the study, which is cradle-to-farm-gate according to the definition by [
12], is represented in
Figure 2. Thus,
Table A2 shows the processes that are included and excluded in the system boundary. Excluded processes are shown with explanations of why they were not included.
2.6. The Functional Unit Chosen for the Study
The functional unit chosen in this study was determined as a single grafted tomato seedling produced during one production season in 2019. For some materials, data obtained from nurseries (e.g., energy, fertilizers, pesticides, disinfectants, plastic sheeting) were compared to the total number of seedlings, and the amount of input per unit seedling was calculated. For some materials (e.g., EPS tray, seedling insert, grafting sticks, grafting clips, peat, perlite, vermiculite, water, packaging) the amount of inputs are either calculated by measuring the weight of specific materials used per grafted tomato seedling or applying formulas according to the statements of nursery authorities.
2.7. Life Cycle Inventory Categories and Processes
In the study, input materials were divided into sub-headings such as energy, fertilizers, pesticides, disinfectants, horticultural substrates, supporting materials, irrigation and transport, and LCA analysis was performed under both general and sub-headings. However, we should also mention that horticultural substrates and supporting materials are also analyzed in the same table because of their relationship.
Table 1 shows the life cycle inventory categories with input material or process names and usage amounts.
2.7.1. Transportation of Materials
The amount of materials used in nurseries and the average distance from the suppliers to the production area was entered into the LCA program and the Ecoinvent process “Transportation, Lorry > 16t, Fleet Average” was selected. Processes within the scope include the transportation of coal, fertilizers, pesticides, disinfectants, horticultural substrates, and other materials from suppliers to the production area.
2.7.2. Irrigation Method
In the nurseries, the main irrigation source is the water drawn from well. The process of water extraction and distribution to seedlings is provided by electrically operated devices. The amount of water used per seedling was determined as 0.950 liters (including both for rootstock and scion when preparing the substrate).
2.7.3. Energy
The energy sources used in the nurseries can be examined in two categories, which are electricity and coal. Unlike [
13], coal is used for greenhouse heating on days with low temperatures. By combustion of the coal, water is heated and it circulates through the pipes placed in the bottom for regulating the heat in the greenhouse. Electricity received from the grid is supplied to electrically operated devices (e.g., production-related devices, computers, lighting, air conditioning). Production-related devices are electrically operated devices such as horticultural substances mixing and dispensing machines, fertilizer dosing devices, water pumps attracting well water, seed drills, and water spraying machines.
2.7.4. Fertilizers
It is thought that population growth in the world is related to the development of technologies used in agriculture. Especially with the synthesis of mineral fertilizers, an increase in fertilizer usage was observed. Considering that almost half of the world’s population is fed with food grown using artificial fertilizers [
7], the environmental impacts of fertilizers used in the production of seedlings, which is the main focus of this study, is of great importance.
In the nurseries, water-soluble solid fertilizers are mixed with water with the help of a fertilizer dosing device and sprayed into the cells where seedlings grow. According to the survey, nitrogen, phosphorus, and potassium (NPK) ratios of fertilizers applied to the tomato seedlings are 20-10-20 and 13-0-46 (potassium nitrate).
2.7.5. Pesticides
At the first stage of analysis, information about the pesticides used by nurseries was retrieved. The active ingredients were calculated as weight and distributed to the categories. Some trademarks contain more than one active ingredient, and these are included in separate pesticide categories.
The compounds used in the “Unspecified Compounds" category are tetramic acid compounds, tetronic acid compounds, and macrocyclic lactone compounds, but in the Ecoinvent life cycle inventory (LCI) database, the “Pesticides Unspecified” category was selected because no specific data on these compounds were found in the inventory.
Table 1 also shows the pesticide compound category names, types, and usage amounts. The compound category names of active ingredients were retrieved from [
14].
2.7.6. Disinfectants
In addition to the pesticides, disinfectants are also indispensable and prevent the spread of possible pests in the cultivation environment since it may adversely affect the production. Hydrogen peroxide, alcohol-based chemicals, and peracetic acid are used as disinfectants. Continuous sterilization of the place of production and materials are made. For instance, EPS trays are disinfected and used two times on average. The workers also use disinfectants in cleaning their clothes to avoid the spreading of possible diseases that may affect seedling health.
2.8. LCA Software and Database
In the study, SimaPro 7.1.8 was used as LCA software, and Ecoinvent 2.0 was used as the LCI database. There are many databases in the literature and they can be used within the same project but using the same database ensures a more consistent analysis. Some of the missing or non-existing materials in the Ecoinvent database were redefined using the existing processes.
2.9. Impact Assessment Method
The methods used in LCA studies can be divided into two groups as midpoint or endpoint. There is no uniform approach within the current literature about which methods to use. Although endpoint methods known to have a higher uncertainty level than midpoint methods [
15], they are more advantageous in terms of concatenation and interpretation of results.
In this study, the “ReCiPe 2008 v.11 Hierarchist Version / Average Weighting Set” endpoint method based on the European normalization values was used. This method expresses the effects of LCA flow on human health, ecosystem, and resource scarcity as disability-adjusted life year (DALY), loss of species during a year (hereinafter “Species.yr”) and US Dollars (USD) [
16].
Table 2 shows the impact categories used in the ReCiPe 1.11 method, showing which type of environmental damage they caused and which units were used.
2.10. Cultivation Environment and Terminology
The main cultivation environment of seedlings changes according to certain factors (e.g., the type of vegetable, grafted or normal, grafting method).
Figure 3 represents the common cultivation environment of grafted tomato seedlings in the nurseries, where the splice grafting method is used.
Grafting: Grafting is the fusion of two plant parts (rootstock and scion) to retrieve a genetically composite organism as a single plant (grafted seedling) by establishing vascular continuity between them [
18,
19]. As a result of the fusion, the scion gains the superior properties of the rootstock.
Splice grafting method: The most common grafting method for tomato [
20] is done by joining the scion onto the rootstock’s stem [
21]. It is the grafting method used in the studied nurseries and both rootstock and scion should be sliced carefully with 45 degrees before the fusion.
Seedling insert: The material produced from polyethylene (PE) and is the main part where the grafted seedlings grow in its cells.
EPS tray: The material produced from EPS foam which is placed under the seedling insert. It isolates the seedling insert and allows the insert to remain stationary.
Rootstock: The root system of the grafted plant supporting and fusing with the scion [
18].
Scion: The splice cut from the donor plant, forming the upper portion of the grafted plant [
18].
Grafting clips: The supporting material produced from silicone which helps to fix and hold the place where the grafting is made.
Grafting stick: The supporting material produced from PE, which fixes grafting clips vertically.
2.11. Supporting Materials and Horticultural Substrates
Seedlings are grown in inserts placed on EPS trays as a backdrop. In grafted seedling production, different EPS trays and seedling inserts are used, which have different cell volumes and cell counts. In the nurseries studied, the cells where the grafted tomato seedlings (rootstock) grow are 50 cc in volume, and the cells where the scions grow is 32 cc, according to authorities interviewed. Also, the scion should not be thicker than the rootstock.
In the horticultural substrates category, peat is used in modern establishments as the main growth medium for seedlings. The variety of peat in seedling production, which is called sphagnum moss peat, is widely used in nurseries across Turkey. However, as a non-renewable resource, sphagnum moss peat is imported from Northern European countries and has no alternatives due to its structural features.
The main horticultural substrate for seedlings consists of peat, perlite, and vermiculite with certain proportions. Peat and perlite are first mixed with water and kept for a while. Peat mixed with water absorbs up to 10 times the weight of peat [
22]. The ratios of the mixture used by the nurseries and the amount of substrate usage per seedling were obtained according to the following equations.
where
pt: peat,
vt: vermiculite,
pr: perlite,
w: water,
V: volume,
d: density,
M: mass.
Perlite and peat mixture is placed in the cells through machines and covered with a vermiculite layer to keep moisture. Besides, the top of the seedlings after the grafting operation is partially covered with plastic sheeting for the success of the operation. Grafting sticks and clips are used additionally in grafted seedlings when compared to normal seedlings. Scions are grown in a different environment, apart from rootstocks, and use separate sizes of trays and inserts. In the nurseries studied, tomato rootstocks grow in inserts with 150 cells having 50 cc cell volume each. EPS trays suitable for the insert size are placed to the bottom of the inserts. Scions are grown in inserts having 32 cc cell volume and containing 216 cells. When rootstocks and scions reach the expected maturity stage, the grafting process is performed in cells where rootstocks are grown. In this case, the inserts are not used again, but the trays are disinfected and used once more on average. After a certain time following grafting operation, grafted seedlings are separated by a special separation method to be put on different inserts (number of cells used per unit seedling doubles). However, before packaging, the empty cells are filled with separated seedlings. When all the separation methods and disinfections were considered, it was calculated that only the scion consumes a half-tray cell as weight while the others (rootstock tray, rootstock insert, scion insert) consume one.
4. Conclusions
Covering the cradle-to-farm-gate period, this study was conducted in nurseries near Antalya province city center, and an LCA analysis of one grafted tomato seedling from the production stage to the packaging phase was made. In this context, according to the results of the analysis, it was found that the highest environmental impact belongs to coal used for greenhouse heating. Secondly, our findings showed that the EPS trays used for cultivation have significant environmental effects.
In the study area, no PV usage as an energy source was found. It was considered that this is due to the fact that the government incentives are not directly given to the producers who adopt PV technologies or other renewable energy sources; instead, incentives are given to public institutions to make nurseries feasible. However, direct incentives (decreasing the installation costs) may result in the adoption of solar energy as a sustainable energy source by the producers.
According to fertilizer analysis results, it was found that ammonium nitrate has the highest effect in three impact categories (CCHH, CCE, PMF) when compared to other fertilizer raw materials used to make an NPK fertilizer. In the fertilizer application phase, it has been found that the presence and proper use of a good fertilizer dosing device contribute to the healthy development of the seedlings by preventing the excess or deficit use of fertilizer so that it prevents nutrient loss which lead to plant loss, and increases the average fertilizer used per plant.
According to pesticide analysis results, it was found that the pesticides in the pyrethroid compounds category have the highest impact on the environment in all categories except freshwater eutrophication. However, direct exposure of personnel to pesticides is also important in terms of human toxicity although sufficient workers’ safety had been ensured in the nurseries where the study was carried out. However, it would not be right to say that the same safety measures are taken in informal nurseries. This informal nursery problem is also underlined by Fidebirlik about the seedling production sector in Turkey.
Regarding the materials used in production, EPS trays have the highest environmental impact in 12 out of 16 categories, and after comparison with other rigid plastic alternatives in terms of production and recycling efficiency, it was determined that HDPE usage is relatively advantageous in several categories including CO2 emissions and recycling. Furthermore, a scenario was created to compare EPS usage with HDPE usage as a tray material. It was found that HDPE tray usage by sterilization (minimum 30 times) has a smaller environmental impact ratio than EPS tray usage (2 times) in terms of human health, ecosystems, and resources impact categories.