Consumo de energía en el manejo de huertas de aguacate en Michoacán, México

Carlos A. Anaya*; Ana Laura Burgos

Centro de Investigaciones en Geografía Ambiental, Universidad Nacional Autónoma de México. Antigua Carretera a Pátzcuaro 8701, colonia Ex-Hacienda de San José de la Huerta, Morelia, Michoacán, C.P. 58190, MÉXICO. Correo-e: carlosanaya.m@gmail.com, tel.: (443) 322 27 77 ext. 42557 (*Autor para correspondencia).

Received: January 20, 2014. ]]> Accepted: February 2, 2015.

Abstract

Efficient fossil energy consumption in agricultural systems is a prerequisite for sustainable agricultural production. Fossil energy consumption (EC) in avocado orchard production in Michoacán, Mexico was analyzed. Process analysis was used to estimate both direct and indirect energy required for the various agricultural operations. Data on fuel and inputs used in production were obtained from structured questionnaires completed by 455 growers. Average annual EC was 28,880 MJ∙ha^-1, but the data ranged between 5,330 and 76,531 MJ∙ha^-1, indicating the co-existence of a great diversity of farming systems. EC in agricultural operations decreased in the following order: fertilization (54.4 %), pest control (39.9 %), weed control (5.6 %) and irrigation (0.2 %). EC in fertilization was positively associated with the economic resources of the growers; and according to recognized fertilization standards, nitrogen fertilizer was applied excessively in 64 % of the orchards. EC in pest control was in the high range reported for fruit-tree crops and, on average, it was 41 % higher in exporting orchards than in those that produce only for the domestic market. EC in avocado production can be significantly reduced by improving fertilization and pest control practices, especially among large- and medium-sized growers.

Keywords: Persea americana Mill., crop management, energy use, environmental indicators, fertilization, pest control.

Resumen

El consumo eficiente de energía fósil, en los sistemas agrícolas, es prerrequisito de sostenibilidad de la producción. Se analizó el consumo de energía fósil (CE) en la producción de aguacate en huertas de Michoacán, México. La energía directa e indirecta consumida en varias operaciones agronómicas fue estimada mediante análisis de procesos. Se obtuvieron datos de combustibles e insumos usados en la producción a través de cuestionarios realizados a 455 productores. El promedio anual del CE fue 28,880 MJ∙ha^-1, pero los valores variaron entre 5,330 y 76,531MJ∙ha^-1, indicando la coexistencia de gran diversidad de modos de producción. El CE en las operaciones agronómicas decreció en el siguiente orden: fertilización (54.4 %), control de plagas (39.9 %), control de hierbas (5.6 %) y riego (0.2 %). El CE en la fertilización fue positivamente asociado con los recursos económicos de los productores; y de acuerdo con estándares de fertilización reconocidos, pudo haber un exceso en la fertilización con nitrógeno en 64 % de las huertas. El CE en el control de plagas estuvo entre los valores más altos reportados en cultivos de árboles frutales y, en promedio, fue 41 % mayor en huertas de exportación que en aquellas que producen sólo para mercado nacional. El CE en la producción de aguacate puede reducirse significativamente mejorando las prácticas de fertilización y control de plagas, especialmente entre los productores grandes y medianos.

Palabras clave: Persea americana Mill., indicadores ambientales, manejo agrícola, fertilización, control de plagas, uso de energía.

The cultivation of avocado (Persea americana Mill.) has shown marked growth in Mexico over the past two decades, as a result of the North American Free Trade Agreement and its growing acceptance in Japan and Europe (Echánove Huacuja, 2008). This expansion has been evident in the state of Michoacán, ranked as the world leader in avocado production with a cultivated area of 153,000 ha and total production of 1.1 million Mg∙year^-1 (Morales-Manilla & Cuevas-García, 2011; Secretaría de Agricultura, Ganadería, Desarrollo Rural, Pesca y Alimentación [SAGARPA], 2013). Similarly, the number of avocado growers in the state has increased dramatically, from 16,150 registered producers in 2007 (Comisión Michoacana del Aguacate [COMA], 2007) to 22,000 estimated for 2012. The market entry of new producers with different degrees of knowledge about growing avocado, occupying new lands with climate and soil not optimal for this purpose, has created a patchwork of orchards with different biophysical conditions and modes of agricultural management. While the expansion of the avocado industry has undoubtedly boosted the regional economy and created jobs, its effects on the environment have created concern in government agencies, producer associations, academic circles, the media and the general public (Barsimantov & Navia Antezana, 2012; Chávez-León et al., 2012).

In the field of sustainable agriculture, an indicative component of a production system's environmental and economic performance is its fossil fuel energy consumption (EC) (Dalgaard, Halberg, & Porter, 2001; Pimentel, Berardi, & Fast, 1983). EC is directly associated with the use of agricultural inputs, production costs and greenhouse gas (GHG) emissions (Lal, 2004; Pimentel, Hepperly, Hanson, Douds, & Seidel, 2005; West & Marland, 2002). Determining EC involves standardizing and synthesizing information, which requires knowing the set of practices used in the production of an agricultural product, and the energy associated with them, including both direct energy sources (diesel fuel, gasoline and electricity), and indirect sources (i.e. use of agricultural inputs whose production and marketing required the consumption of fossil energy) (Dalgaard et al., 2001). EC analysis identifies practices with significant energy use, makes comparisons between different management modes to choose those strategies with greater efficiency, and establishes trends and variations in EC over time on different levels of agricultural organization (Jones, 1989). Because of the potential for assessing farming practices in terms of energy efficiency and reduced GHG emissions, EC quantifications have been made for different crops worldwide, including fruit-tree crops such as citrus production (Ozkan, Akcaoz, & Karadeniz, 2004), apples (Reganold, Glover, Andrews, & Hinman, 2001), and pear (Liu, Langer, Høgh-Jensen, & Egelyng, 2010). In these crops it has been observed, for example, that the activity requiring the most fossil energy is fertilization, followed by pest and disease control, and that EC may vary among management systems (e.g. conventional, organic and integrated).

As in other cases, knowledge of EC in avocado growing provides elements to assess its sustainability and provide notice of the need to incorporate energy conservation practices. The aim of this study was to analyze the patterns of fossil EC in the management of avocado orchards in Michoacán. Therefore, we sought to identify the most energy-demanding agricultural operations and the main factors explaining EC variability among orchards at the regional level. The analysis was guided by two working hypotheses: (1) given the great heterogeneity of avocado producers and biophysical production conditions in Michoacán, it is to be expected that EC will vary widely and that this is influenced by the socio-economic characteristics of the producers and the biophysical aspects of the orchards, and (2) the agricultural activity with the highest EC in avocado orchard management will be fertilization as has been observed in other fruit-tree crops; however, given the increasing incidence of pests, diseases, and export demands, phytosanitary control is also expected to have high EC.

MATERIALS AND METHODS

Study area

The study was conducted in the avocado-producing region of Michoacán, Mexico, encompassing a transverse strip between the counties of Cotija to the west and Tuxpan to the east, between 1,400 and 2,200 m above sea level, along the 19º N parallel and between the 100º to 103º W meridians (Figure 1). This area has a temperate sub-humid C(w2) climate, and tropical sub-humid ((A)C(w1) and (A)C(w2)) climates, with annual rainfall ranging between 800 to 1,700 mm concentrated between May and October, and monthly high and low temperatures of 27 and 12 ºC, respectively (Gutiérrez- Contreras, Lara-Chávez, Guillén-Andrade, & Chávez- Bárcenas, 2010).

Data collection on orchard management

Data collection was done through direct surveys. These involved applying a structured questionnaire to a random sample of growers who perform agricultural operations in orchards older than eight years of age, excluding those related to harvesting and packing which are carried out by the packing industry or local merchants (Salazar-García, Zamora-Cuevas, & Vega-López, 2005). Sampling was performed in the jurisdictions of nine of the 15 Local Plant Health Boards (known by the Spanish acronym JLSV) in Michoacán. The JLSV are auxiliary bodies of the Secretariat of Agriculture, Livestock, Rural Development, Fisheries and Food (known by the Spanish acronym SAGARPA) in Mexico. Their function is to regulate the output of fruit production and oversee the application of health standards in all orchards. The JLSV participants in this study were: the Gral. Francisco J. Mújica JLSV, which serves the counties of Cotija, Tangamandapio, Tocumbo and Tingüindin; the Oriente JLSV, which operates in six counties adjacent to the State of Mexico and the JLSV of the counties of Tacámbaro, Ario de Rosales, Uruapan, San Juan Nuevo, Tancítaro, Peribán and Los Reyes. These JLSV were selected because of their location along the avocado-growing strip (Figure 1), which allowed capturing the production methods that exist in different climatic, geographic and social contexts. It should be noted that the JLSV were instrumental in this work since they facilitated the formal approach to the growers for the application of the surveys. The questionnaire included 78 questions designed to elicit detailed information about the agricultural practices of fertilization, pest control, weed control and irrigation, including the scheduling of these practices (i.e. frequency and dates on which they are performed) and the type and quantity of inputs used in them. Questions on the characteristics of the orchard and its production, such as locality-level location, dominant relief, infrastructure, equipment, cultivated varieties, density, plantation age, average yield and sales market, were also included. No questions were asked concerning the climatic characteristics of precipitation and temperature at the orchard location, because they were obtained through the generation of isohyets and isotherms in GIS (ESRI, Inc., 2008), using for this purpose the database of the national network of meteorological stations contained in the Software ERIC III (Instituto Mexicano de Tecnología del Agua [IMTA], 2013). In the case of growers with more than one orchard, the questionnaire asked them to provide management information only about their largest orchard. Before applying the questionnaire, it was piloted and validated with growers belonging to the Local Avocado Growers Association of Uruapan, Michoacán (known by the Spanish acronym AALPAUM). A total of 520 surveys were applied between June 2010 and November 2011. After review, 65 surveys were removed from the sample due to inconsistencies or incomplete answers, so only 455 were included in the analysis, representing 4 % of the approximately 11,000 registered producers (COMA, 2007). The sample covered a wide range of production conditions (Table 1).

Calculation of energy consumption

Energy costs were expressed in Joules per unit area, assuming an annual production cycle (J∙ha-1∙year-1). No units relating to the energy prices involved in orchard management were used, because the interest of the study was in energy consumption, not the costs thereof. This allowed the comparative analysis of EC with other horticultural crops reported by studies in different countries. The study was restricted to fossil EC of direct and indirect sources, excluding solar energy and human labor. The calculation was performed using the process analysis method based on the determination of the physical flows of materials, in accordance with the following equation (Hülsbergen et al., 2001):

Statistical analyzes

The total energy consumption (EC_t) of each production unit was calculated from the sum of the EC in the farming activities of fertilization (EC_fert), pest and disease control (EC_pd), weed control (EC_weed) and irrigation (EC_irrig). To analyze the variation in EC_t in the sample of producers (n = 455), its coefficient of variation was determined and its frequency distribution was described by a histogram and testing of fit to normal and gamma distributions. To assess whether EC_t has an influence on avocado yields (i.e. productivity; Mg∙ha^-1∙year^-1), a regression analysis between the two variables was performed. To find the explanatory factors of EC in the production units, we carried out Pearson's correlation analysis and stepwise regression analysis between EC_t and the EC of particular agricultural activities with a set of seven variables, including climatic characteristics at the orchard's location (i.e. mean annual precipitation and temperature), structural characteristics (i.e. orchard age and planting density), characteristics of the producer's economic capability (i.e. total cultivated area and own equipment), and destination sales point (i.e. domestic and export markets). In the regression analyzes only explanatory variables that previously correlated significantly with EC were included (Zar, 1999). According to Spearman's rank correlation coefficient, total cultivated area and equipment availability had a positively significant correlation (r = 0.66, t₍₄₅₃₎ = 18.8, P < 0.0001); therefore, only total cultivated area as an explanatory variable associated with the producer's economic capability was used. The effect of the binary marketing variable was only assessed on EC_t, for which the Student's t- test was used. Statistical analyzes were performed with STATISTICA 7 software (StatSoft Inc., 2004).

RESULTS

The EC_t in the management of avocado orchards had a high coefficient of variation, 41 %. Its values ranged from 5,330 to 76,531 MJ∙ha^-1∙year^-1, averaging (± 1 e.e.) 28,880 ± 560 MJ∙ha^-1∙year^-1 (Table 3). The frequency distribution of the EC_t values constructed with 13 classes did not fit normal distribution (X² = 22.7, P = 0.0009), but it did with gamma distributi on (X² = 5.04; P = 0.54). This distribution showed a positive bias (0.6 ± 0.11), with a relatively higher number of below-average values (Figure 2). Of the total data, 56 % showed EC_t of between 20,000 and 40,000 MJ∙ha∙year^-1, and 28 and 16 % had values higher and lower than this range, respectively.

Avocado yield per orchard ranged from 4 to 30 Mg∙ha^-1∙year^-1, averaging 12 ± 0.26 Mg∙ha^-1∙year^-1. Regression analysis showed that EC_t explained 7 % of this variation (r² = 0.07, P < 0.001).

Regarding the explanatory variables of EC_t variability, it was found that it correlated positively with four of the five analyzed variables (Table 4), with the following order of importance: total cultivated area, annual precipitation, orchard age and planting density. However, multiple regression analysis showed that together these four variables explained only 15.5 % of the variation in EC_t (r²_multiple = 0.15; f _(3,442) = 26; P <0.001). On the other hand, EC_t was significantly higher in orchards producing avocado for export sales rather than for the domestic market (t = 5.3; fd = 453; P < 0.0001). This difference was primarily attributable to EC_pd, which was 41.8 % higher in orchards with export production (Figure 3).

The analysis of EC_t by agricultural operation showed that EC_fert was the most energy-demanding activity, representing on average 54.4 % of EC_t with absolute consumption of 15,665 ± 378 MJ∙ha∙year^-1 (Table 3). For its part, EC_pd was the second highest with 11,535 ± 343 MJ∙ha^-1∙year^-1, corresponding to 39.9 % of EC_t, whereas EC_weed and EC_irrig accounted for 5.6 and 0.2 % of EC_t, respectively. When ECEC_irrig was calculated, only for the group of orchards with irrigation, it had an average value of 399 ± 36 MJ∙ha^-1∙year^-1, with high variation (CV = 74 %).

According to the correlation and regression analyses, the EC of the individual agricultural operations was influenced differentially by the independent variables studied. EC_fert positively correlated with total cultivated area, planting density and to a lesser degree with orchard age and temperature (Table 4). These four variables together explained 20.5 % of the variation in EC_fert (r²_multiple = 0.205; f_(3,442) = 38; P < 0.001). EC_pd positively correlated with precipitation, orchard age and to a lesser degree with total cultivated area (Table 4). However, these variables only explained 12.7 % of data variation (r²_multiple = 0.127; f_(3,442)= 32; P < 0.001). EC_weed positively correlated with total cultivated area, planting density and precipitation, which explained 13.5 % of its variation (r²_multiple = 0.135; f_(3,435) = 23; P < 0.001).

DISCUSSION

As expected, EC_t in avocado production showed high variation among orchards. This variation indicates that there is a wide variety of avocado farming systems in Michoacán. The EC_t fit to gamma distribution and the positive bias of this distribution show that EC_t is distributed asymmetrically with a concentration of cases at lower values. This distribution may be related to the dominance of small producers in the sample (Table 1), since they showed a tendency to lower EC_t, according to regression analysis. As in our sample, in the universe of Michoacán avocado growers, small producers numerically dominate (72 %) over medium-sized (18 %) and large ones (10 %) (COMA, 2007), so the observed pattern may be representative of the crop's production statewide.

This study generated the first EC data for avocado production available in the literature. Comparison of EC_t in avocado with those reported in 11 fruit-tree crops in various parts of the world (Table 5) shows that the average EC_t for avocado production is among the lowest values reported, slightly above EC_t reported in the production of apricots and cherries in Turkey (Demircan, Ekinci, Keener, Akbolat, & Ekinci, 2006; Gezer, Acaroğlu, & Haciseferoğullari, 2003) and similar to that determined for the production of kiwi in Iran (Mohammadi, Rafiee, Mohtasebi, & Rafiee, 2010). This suggests that avocado production in Michoacán involves moderate energy consumption. However, this comparison at EC_t level should be taken with caution due mainly to the disparity of energy consumption sources considered in each study. For example, human labor and energy consumption for producing machinery are not taken into account in this study, unlike other studies.

As expected, the analysis of EC by farming operation showed that fertilization and pest management are the most energy-demanding activities in avocado production. These activities have also been considered as the most important in the context of fossil EC in other fruit-tree crops worldwide (Table 5).

Regarding EC_fert, its average in avocado falls in the middle range for fruit-tree crops, with a value similar to thatf of pear fertilization in China (Liu et al., 2010) (Table 5). However, in relative terms, EC_fert in avocado accounted for the highest value (54.4 % of EC_t), along with that used in tangerine production in Iran (61 %; Mohammadshirazi, Akram, Rafiee, Mousavi Avval, & Bagheri Kalhor, 2012). To explore whether this high relative value of EC_fert reflects disproportionate energy consumption due to improper fertilization, nitrogen (N) application was reviewed using the data collected. This element is a good indicator of the fertilization practice because it is applied annually, owing to its great influence on crop growth (Lahav & Kadman, 1980). While the N fertilization dose in avocado depends on several factors, including the availability of this nutrient in the soil and the age of the trees, experimental studies have determined that N rates between 55 and 180 kg∙ha^-1∙year^-1 are suitable for productions of 10 to 12 Mg∙ha^-1∙year^-1 in a wide variety of soils and conditions (Embleton & Jones, 1965; Lahav, 1995; Lahav & Kadman, 1980; Loupassaki, 1995; Lovatt, 2001). In this study, the average application of N in chemical form was 158 kg∙ha^-1∙year^-1; however, manure is also applied annually. By including the N contained in this source, which has an N content of 5.6 kg per wet ton of manure (Pimentel et al., 1983), the average N application was 211 kg∙ha^-1∙year^-1, putting 64 % of the orchards at doses above the recommended maximum of 180 kg∙ha^-1 (Figure 4). Excess N addition in avocado orchards is a problem also reported in the USA (Embleton & Jones, 1965; Kiggundu, Migliaccio, Schaffer, Li, & Crane, 2012; Yates, Meyer, & Arpaia, 1992) and Michoacán (Tapia-Vargas, Larios-Guzmám, Contreras, Vidales-Fernández, & Barradas, 2012). In the present study, the positive correlation between EC_fert and total cultivated area indicates that fertilizer application tends to be higher among large producers. This pattern may be associated with their greater economic capability, which can incline them towards over-fertilization, either due to lack of knowledge or carelessness in their pursuit of higher yields. In this context, large producers can significantly reduce energy consumption without affecting production by improving fertilization efficiency. Greater efficiency in adding fertilizer is not only desirable in the context of efficient use of energy, but also in the sense that excessive fertilizer use is associated with environmental problems arising from leachates entering water bodies.

With regard to EC in the use of pesticides, avocado growing stands out for its high absolute and relative values ( 39 % of EC_t) compared to other fruit-tree crops presented in Table 5, except apple growing with traditional management in the USA and tangerine growing in Iran, which emphasizes the importance of phytosanitary control in avocado production. This observation may be associated with the difficulty in carrying out phytosanitary control in avocado since it is affected by more than 15 diseases and pests, including some of great economic importance such as thrips (Thysanoptera), avocado scab (Sphaceloma perseae Jenk), seed borers (Conotrachelus aguacatae Barber, Stenoma catenifer Walsingham and Heilipus lauri Boheman) and stem borers (Copturus aguacatae Kissinger) which are catalogued as quarantine pests (Hoddle, 2004; Hoddle, Jetter, & Morse, 2003; Pegg et al., 2002). Among the factors that explain the variation in EC_pd in Michoacán avocado orchards, the sales market stands out, as EC_pd is 41 % higher in production for the export market. This may be because the general pest management protocol in export orchards is stricter than in those aimed at the domestic market, since they have to regularly undergo health certification processes in order to export their production (Peterson & Orden, 2008). These effects of the international market on farming costs and management systems are the focus of current debate given the large-scale opening up of global markets and the different business management capacities of countries (Pretty et al., 2010). Regardless of the type oforchard, phytosanitary control in Michoacán does not include widespread pest monitoring and biological control; by contrast, it is commonly done through the spraying of chemical pesticides and mineral fungicides, scheduling four to 12 preventative applications per year (data not shown). This practice results in higher energy consumption and economic costs, along with negative environmental impacts through the release of large amounts of toxic substances into the environment (Mangiafico et al., 2009; Chávez-León et al., 2012). The dissemination of better pest management practices, with a consequent reduction in energy consumption, should include various courses of action, such as improved knowledge of pest dynamics under different climatic conditions, increased farmer training in alternative integrated pest management practices and implementation of these practices in a coordinated manner at different levels, from the plot to the region, as well as international issues of trade and regulatory agreements.

CONCLUSIONS

Fossil EC in avocado production in Michoacán exhibits wide variation among orchards, which reflects the great diversity in forms of production. Compared with other fruit-tree crops in the world, EC in avocado is moderate. However, at the level of farming activity, concerns are raised in relation to EC in fertilization and phytosanitary control. EC in fertilization is high among medium- and large-scale farmers, who in a significant proportion may be using fertilizers excessively. EC in phytosanitary control of avocado is high compared to other fruit-tree crops, and it was higher in orchards with export production than in those that sell to the domestic market, which shows the direct influence of the market on management and EC in avocado production in Michoacán. EC in Michoacán avocado production can be significantly reduced by adopting better fertilization and pest control practices, especially among medium-and large-scale producers.

ACKNOWLEDGMENTS

This manuscript is a product of the "Ecological impact of avocado cultivation in the State of Michoacán" project, funded by COFUPRO - Michoacán Unit between 2010 and 2012. The authors thank the AALPAUM and the JLSV of Uruapan, Michoacán and the Local Avocado Plant Health Boards of Ario de Rosales, F. J. Múgica, Los Reyes, Nuevo San Juan, Oriente, Peribán, Tacámbaro and Tancítaro for their collaboration in this work. Iván Solorio and Dorian Anguiano conducted field interviews, and Gabriela Cuevas prepared the spatial analysis of climatic variables and Figure 1. Marta Astier and Yair Merlín provided support in the selection and estimation of energy equivalents. The manuscript benefited substantially from suggestions made by Ann Grant, Adrián Ghilardi, editor Juan Enrique Rodríguez Pérez and an anonymous reviewer.

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