Energy contributions and greenhouse gas emissions in pepper (Capsicum annuum L.) cultivation with plastic mulch

ABSTRACT The objective of this work was to determine the use and efficiency of energy and to quantify the greenhouse gas (GHG) emissions, per hectare, for the cultivation of pepper, Capsicum anuum L., hybrid MIRELLA F1, using plastic mulch in the open-field. The assays were performed in a farm of Puerto La Boca (1° 20’ 51” S and 80° 43’ 51” W), the precinct of the Puerto Cayo parish of Jipijapa Municipality, Manabí province, Ecuador. The data was collected through field research, between March and September 2021, under observation and timing techniques. There was evidence of energy consumption and production (in the form of pepper berries) of 18,442.29 and 27,702.74 MJ ha-1, respectively, and a total GHG emission of 3,058.90 kg CO2-eq ha-1. The energy efficiency was determined at 1.50, the energy productivity 1.88 kg MJ-1, the specific energy 0.53 MJ kg-1, and the net energy 8,858.46 MJ ha-1. The quotas of direct and indirect energies were calculated at 9,513.15 and 8,929.15 MJ ha-1, respectively, and the proportion of renewable and non-renewable energies at 12,994.03 and 5,448.27 MJ ha-1, respectively. The GHG index per kg of MIRELLA F1 pepper yield was 0.088.

Agricultural actions are responsible for approximately 20% of greenhouse gas (GHG) emissions globally (Ozbek et al., 2021).In Latin America, GHG emissions are continuously increasing, which reinforces urgent climate action by governments, at the national and regional levels, and by non-state actors (Comisión Europea, 2019).
In 2021, Ecuador's energy consumption was around 93.5 million BOE (barrels of oil equivalent).The agri-cultural, fishing, and mining component required 1,121 thousand BOE.GHG emissions, made up of 99.33% CO 2 , 0.22% N 2 O and 0.45% CH 4 , generated by this sector were 447 thousand t CO 2 eq (IIGE, 2022).However, within the framework of the Paris Agreement, Ecuador, had projected to reduce emissions by 9% in the energy, industry, waste, and agricultural sectors (Toulkeridis et al., 2020).
The pepper (Capsicum annuum, L. 1753) is native to Tropical America and is the second vegetable consumed worldwide (Hulse-Kemp et al., 2019).Ecuador allocates 2,232 ha for its cultivation, with approximate yields of The area of intensive farming systems (mulches, tunnels, and plastic greenhouses) has been expanding in recent years (Khoshnevisan et al., 2014).Polyethylene mulch is widely used in intensive agricultural production systems.
It provides advantages for crops both from the agronomic and phytosanitary points of view (Marín-Guirao et al., 2022).In this sense, in the farm under study, the technique of agricultural mulch, of the polyethylene type, was incorporated in 2020 in an open-field productive system, and the use of genetic materials adapted to the area, such as the MIRELA F1 hybrid pepper, relieving this way the direct sowing.
International studies, like those of Ozbek et al. (2021) and Baran et al. (2020), determined the energy efficiency and GHG emissions of onion and almond crops, respectively; Houshyar et al. (2015) studied the energy consumption in tomato production and Eren et al. (2019a) worked on GHG emissions in various crops in Turkey, in the open-field production system.In Ecuador, no related publications were found in these fields.In consequence, the objective of this work was to determine the use and efficiency of energy and quantify emissions of greenhouse gases (GHG), per hectare, in the cultivation of the MIRE-LLA F1 hybrid pepper, with the use of plastic mulch in an open-field production system, on a farm in the Puerto La Boca compound of the Puerto Cayo parish of the Jipijapa Municipality, Manabí province, Ecuador.

Edaphoclimatic characterization of Puerto Cayo -Puerto la Boca
The Puerto Cayo rural parish, a recreational area that in-  2015).

Experimental site
The

Labors for the production of the pepper crop
The tillage of the land was carried out with the Baldán CRSG 24-disc (24 in) eccentric pull harrow with a structural weight of 1,950 kg, working width of 2,700 mm (Federal, 2005), a useful life of 5,000 h (Frank, 1998), driven by the coupling system, and coupled to the hydraulic system of tractor Valtra Valmet HiTech 1850 of 92 kW with a construction mass of 5,090 kg (AgriDatos, 2021) and economic life of 12,000 h (Frank, 1998).The average working depth of the mechanized set was 0.228 m.
For the construction of ridges (0.30 x 1 m), the "lampa" (shovel) manual tool was used; later the drip irrigation tapes (a line) were laid and covered with plastic mulch.
For the transplantation of the MIRELLA F1 hybrid pepper, the hand tool was used as a skewer and 24,000 units of seedling ha -1 of between 20-22 days after germination with an average weight of 0.0292 kg seedling -1 , determined with the CAMRY ACS-30-JC21 digital scale.The MIRELLA Energy contributions and greenhouse gas emissions in pepper (Capsicum annuum L.) cultivation with plastic mulch F1 genetic material and plastic mulch were supplied by a commercial agricultural input company.
Pest and disease control was carried out with a 20 L backpack-type pump.The agricultural insecticides Randiant, Match, and Movento Smart were used, alternating their application.On the other hand, weeding was also executed manually.
For irrigation and fertilization, an electric pump (2 hp) was used, which extracted water from a deep well built 80 m from the farm.Water to the pepper crop was supplied by connecting a polyvinyl chloride (PVC) pipe to the pump and drip irrigation tapes, depending on weather conditions.
Harvesting was done manually and sequentially due to the productive cycle of this hybrid.The weight of the pepper berries reached 0.165 kg on average.Finally, the total yield of the product amounted to 34,628.43 kg ha -1 .
For the commercialization of the product, the buyers went to the farm to stock up and take it to other locations for sale and final distribution.

Methods
Through field research, under direct observation and timing techniques, supported by formats designed for recording agricultural work daily, the number of inputs needed was known (machines, human labor, diesel, biocides, fertilizers, electricity, water for irrigation, and seeds -seedlings), product yield (output), and intensity in the execution of agricultural activities of the MIRELLA F1 hybrid pepper crop.
The documentary research allowed obtaining energy conversion factors and GHG emissions for inputs and outputs in the production of this solanaceous; in addition, the methodologies necessary to achieve the proposed objectives.

Efficiency and use of energy
To obtain the total energy input of the inputs and output, by yield in the form of pepper berries, the quantities of inputs used (machines, human labor, diesel, biocides, fertilizers, electricity, water for irrigation, seeds -seedlings) and output (pepper production, kg), were multiplied by conversion factors to correspondence (Canakci & Akinci, 2006;Pishgar-Komleh et al., 2012).The energy equivalents are shown in Table 1.The energy of the machines was determined with equation (1), according to Canakci & Akinci (2006).
where M pe , is the energy of machines (MJ ha -1 ); G, the weight of tractor and machine (kg); M p , the energetic equivalent of production of tractor and machine (MJ kg -1 ); T, the economic life of tractor and machine (h); and W, the effective field capacity (ha h -1 ).
The effective field capacity (0.75 ha h -1 ) of the Valtra Valmet HiTech agricultural tractor and Baldán CRSG harrow, was obtained from the relationship between the worked area of 1 ha and the total time to carry it out, 1.33 h.
The equivalent energy of production of the tractor and agricultural implement "Mp" (equation 1), is made up of the amount of energy, in the materials, in the manufacturing process, the transport to the consumer, and the energy sequestered by repairs (Kitani, 1999).
The specific fuel expenditure of the agricultural complex, per unit of work (L ha -1 ), was established through measurements at the beginning and end of the day occupied for this purpose (Quimis-Guerrido & Shkiliova, 2019).
Through the quantification of input and output energies, the energy indices were determined.These indices are a tool that allows systems to be compared and their components to be studied (Naderi et al., 2019).They include energy use efficiency, energy productivity, specific energy, and net energy, which were calculated by equations 2, 3, 4, and 5, respectively (Mohammadi-Barsari et al., 2016;Naderi et al., 2019).
Efficiency of energy use = Output energy (MJ ha -1 ) / Input energy (MJ ha -1 ) (2) Energy needs, in agricultural systems, can be divided into direct and indirect or renewable and non-renewable forms (Mohammadi & Omid, 2010).
Direct energies included human labor, diesel, electricity, and water for irrigation, while indirect energies included energy incorporated into the machinery, fertilizers, biocides, and seeds-seedlings.On the other hand, non-renewable energies, were electricity, machinery, fertilizers, biocides, and diesel fuel; while renewables were human labor, water for irrigation, and seeds -seedlings (Heidari & Omid, 2011).In this study, solar energy was not considered.
where R (i) is the application rate of input i (unit ha -1 ) and EF (i) is the GHG emission coefficient of input i (kg CO 2eq.unit -1 ).
The index to evaluate the amount of kg CO 2 -eq emitted per kg of yield was also calculated with equation ( 8) (Khoshnevisan et al., 2014;Houshyar et al., 2015).
where I GEI is the GHG emission coefficient and Y is the yield in kg ha -1 of pepper crop.
Table 2 illustrates the GHG emission coefficients of inputs and production.
Data collection and recording, as well as basic arithmetic operations, were worked on Excel spreadsheets.

RESULTS
Agricultural activities were developed such as: tilling the land which occupied 1-day laborer and 1.33 h (March/10).

Determination of and use of energy in pepper cultivation
The inputs with the greatest contribution to energy consumption were seeds-seedlings, followed by water for irrigation and human work (Table 3).On the contrary, the inputs, use of machinery, fertilizers, biocides, diesel, and electricity presented a lower amount, in the structural composition of the total energy consumption, which was lower than the amount of total output energy generated by the yield of the pepper (in the form of berries) MIRELA F1 hybrid.

Determination of GHG emissions -carbon footprint in pepper production
GHG emissions in pepper cultivation amounted to 3,058.90 kg CO 2 -eq ha -1 .A higher proportion of CO 2 was emitted by the use of the input seeds-seedlings 1,394.59kg ha -1 (45.59%).They were followed by emissions derived from human work and irrigation water of 902.53 and 593.13 kg ha -1 , with a proportion of 29.51 and 19.39%, respectively.Table 4 illustrates records of partial and total emissions derived from the crop.
Other energy inputs, use of machinery, fertilizers, biocides, and electricity emitted CO 2 in a proportion of less than 1%.Finally, the relationship between GHG emissions and the yield of the MIRELLA F1 hybrid pepper was 0.088.

DISCUSSION
Analysis of the energy system is essential to take advantage of limited resources and improve production processes in agriculture (Naderi et al., 2019).The total input energy equivalent amounted to 18,442.29 MJ ha -1 in the pepper crop evaluated in this work.Among the main contributing energy inputs in the cultivation of the MIRELA F1 hybrid pepper were seedlings 38%, followed by irrigation water 19.30%, and human labor 13.16%.In this sense, the number of seeds-seedlings is a function of the sowing population, which also influences the water requirement together with edaphoclimatic factors of the production site and the type of crop developed.Although human labor is among the contributing inputs, the incorporation of the agricultural mulch technique (plastic mulch) decreased the use of biocides, the workforce for their application, and for weeding.
Within the same topic, crop rotation is an important factor for soil conservation.Evidently, the MIRELLA F1 hybrid genetic material showed satisfactory edaphoclimatic adaptability.The adequate agronomic practices allowed it to extend the production cycle, characteristic of this hybrid, making it possible to collect sequential crops, every 14 days, between July and September.On the other hand, fertilization (fertigation) was controlled and effective.Likewise, the use of diesel fuel was limited by the scarce mechanization of agricultural operations on the farm and specifically in this crop.
The energy efficiency of 1.50 meant that, by consuming one MJ of input energy, 1.50 were produced.In this sense, Ozbek et al. (2021), in onion cultivation with a predominance of fertilizers, 60.43% reported an energy ratio of 2.21.Baran et al. (2020) in the organic production of almonds, whose contributing inputs to energy consumption were diesel and use of machinery 37.21 and 27.56%, respectively, obtained an energy ratio of 2.02.For their part, Houshyar et al. (2015), in tomato cultivation reported an energy ratio of 1.16, the most contributing inputs were fertilizers (30%), farm manure (28%), and irrigation water (20%).For the cultivation of the MIRELLA F1 hybrid pepper, the quotas of direct energy composed of human labor, diesel fuel, electricity, and irrigation water exceeded that of indirect energy (machinery, biocides, fertilizers, and seed-seedlings) by 3.16%.In addition, the proportions of renewable energies, derived from energy inputs, exceeded non-renewable energies by 40.92%.This is consistent with the importance of increasing the amount of renewable energy in energy consumption exposed by (Tan, 2018).
In contrast, Ozbek et al. (2021) reported that, in onion cultivation, there was a predominance of non-renewable energies in 61.26% compared to renewables, recommending reducing chemical fertilizers and using animal manure.
The total GHG emission generated by the MIRELLA F1 hybrid pepper crop was 3,058.90kg CO 2 -eq ha -1.The most important input was seedlings with 45.59%.The GHG index registered 0.088 kg CO 2 -eq per kg of product yield.Ozbek et al. (2021), in onion cultivation, calculated total emissions of 2,920.73kg CO 2 -eq ha -1 , the contributing inputs were human labor 42.13% and fertilizers 37.71%, and a GHG index of 0.094 kg CO 2 -eq per kg of product yield.Baran et al. (2020) reported total GHG emissions in the organic almond production for 2,518.46kg CO 2 -eq ha -1 , human labor with 54.20% was presented as the pre-dominant input, and GHG index of 1.80 kg CO 2 -eq per kg of product yield.Eren et al. (2019a) reported emissions of 4,742.69 and 1,933.61kg CO 2 -eq ha -1 , in sugar beet and pea crops, seeds, and human labor were presented as inputs of greater proportion with 73.07 and 33.36 %, and GHG indices of 0.070 and 0.090 kg CO 2 -eq per kg of product yield, respectively.Also, Eren, et al. (2019b), in tobacco cultivation, reported total GHG emissions of 6,604.68 kg CO 2 -eq ha-1, the predominant input was human labor in a proportion of 67.62% and GHG index of 6.29 kg CO 2 -eq per kg yield of tobacco leaves.

CONCLUSIONS
The cultivation of pepper, hybrid MIRELLA F1, using plastic mulch under an open-field production system and under the conditions of a farm located in Puerto La Boca area, registered energy consumption and production (in the form of pepper berries) of 18,442.29 and 27,702.74MJ ha -1 , respectively.Energy efficiency, energy productivity, specific energy, and net energy were calculated as 1.50; 1.88 kg MJ -1 ; 0.53 MJ kg -1 , and 9,260.45MJ ha -1 , respectively, and were considered satisfactory.The share of direct energy exceeds that of indirect energy by 3.16% and the proportion of renewable to non-renewable energy by 40.92%, which refers to an environmentally responsible agricultural operation.Total GHG emissions registered 3,058.90kg CO 2 -eq ha -1 and the GHG index was 0.088 kg CO 2 -eq per kg of product yield.Agriculture provides food sovereignty and economic income to the people; therefore, its sustainability is a right.
8,101 t (FAO, 2019).Pepper cultivars are made in the openfield and greenhouse production systems, mainly located in Byron Leonardo Quimis-Guerrido et al. the provinces Guayas, Santa Elena, Manabí in the Coastal region, and Chimborazo, Loja, and Imbabura in the Sierra -high altitude region (Chuquitarco et al., 2021).In the province of Manabí, the Jipijapa Municipality has 90,129 ha for agricultural activities (INEC 2021).In the Puerto Cayo parish, 47 Agricultural Production Units (UPA) cultivate peppers in the open-field and in an artisanal way, like 40 families in the Puerto La Boca area that sustain incomes with short-cycle agriculture (GADPRPC, 2022).

Figure 1 :
Figure 1: Percentage structure of energy inputs.

Table 1 :
Energy conversion factors associated with inputs and outputs in pepper cultivation Byron Leonardo Quimis-Guerrido et al.

Table 2 :
GHG emission coefficients associated with inputs and outputs in pepper cultivation

Table 3 :
Inputs and outputs of energy in pepper cultivation DE-Direct Energies; IE-Indirect energies; RE-Renewable energies; NRE-Non-renewable energies.

Table 4 :
Carbon footprint in open-field pepper production

Inputs Unit Coefficient GHG (kg CO 2 -eq unit -1 ) Inputs (unit ha -1 ) Emissions GHG (kg CO 2 -eq ha -1 ) %
Houshyar et al. (2015)y of 1.88 kg MJ -1 indicates that, per input MJ, 1.88 kg of product are produced.This value exceeds that presented byOzbek et al. (2021)andAllali et al. (2016)in onion cultivation of 1.38 and 0.54 kg MJ -1 , respectively, byHoushyar et al. (2015)of 1.45 kg MJ -1 in Khoshnevisan et al. (2014)values for net energy.Khoshnevisan et al. (2014)argue that the net energy can be modified, either by reducing the input energies or by increasing the yield using the same or lower input energies.