http://dx.doi.org/10.15446/agron.colomb.v32n1.38679

¹ Technical Assessor. Bogota (Colombia).
² Department of Agronomy, Faculty of Agricultural Sciences, Universidad Nacional de Colombia. Bogota (Colombia). gaplazat@unal.edu.co

ABSTRACT

Agricultural production changes constantly and producers have to be able to use resources more efficiently to obtain a greater yield and improve quality at the lowest possible cost. Consequently, the objective of this paper was to carry out a technical evaluation of the fertilization programs for flue-cured tobacco farming in the municipalities of Campoalegre and Garzon, located in the department of Huila, Colombia. Seven treatments, corresponding to six fertilization alternatives (three dosages and two application sources) and the conventional treatment carried out by producers (the control) were evaluated. When the leaves reached ripeness for harvest, they were harvested, cured and later classified and weighed to measure the yield and the quality obtained from the treatments. For the technical and economic analysis, the yield, fertilization cost, net and gross income, and the purchase quality were taken into account. The municipality of Campoalegre showed a greater average yield (3,080 kg ha^-1) over Garzon (2,640 kg ha^-1). For both municipalities, the highest costs were experienced with the 150% fertilization treatment and the use of ammonium sulphate (AMS). For Campoalegre, the greatest yield was obtained without the use of ammonium sulphate at all three dosages. In Garzon, the greatest yield was obtained with the 100% dosage with or without the use of AMS and the conventional treatment carried out by the producers. The best cost-benefit ratio in Campoalegre was obtained with the 50% dosage of fertilization recommended without use of AMS and, in Garzon, it was obtained with the conventional treatment.

Key words: fertilization, economic analysis, cost benefit analysis, Nicotiana tabacum L.

RESUMEN

La producción agrícola es dinámica y competitiva, y los productores deben ser más eficientes en la utilización de los recursos para obtener mayor rendimiento y mejor calidad al menor costo posible. Por lo anterior, el objetivo del presente trabajo fue realizar una evaluación técnica de programas de fertilización en el cultivo de tabaco Virginia, en los municipios de Campoalegre y Garzón del departamento del Huila. Se evaluaron siete tratamientos correspondientes a seis alternativas de fertilización (tres dosis y dos fuentes de aplicación) y un testigo comercial. Cuando las hojas alcanzaban la madurez de recolección, se cosecharon, se curaron y posteriormente se clasificaron y pesaron para obtener el rendimiento y la calidad por tratamiento. Para el análisis técnico y económico se tuvo en cuenta el rendimiento, costo de la fertilización, ingreso bruto y neto, y calidad de compra. El municipio de Campoalegre presentó mayor rendimiento promedio (3.080 kg ha^-1) con respecto a Garzón (2.640 kg ha^-1). Para los dos municipios los costos más altos se presentaron en los tratamientos con dosis del 150% de la fertilización y la utilización de sulfato de amonio (SAM). Para Campoalegre, los mayores rendimientos se obtuvieron con la no utilización de SAM a las tres dosis. En Garzón, los mayores rendimientos se obtuvieron con la dosis al 100% con y sin aplicación de SAM y el testigo comercial. La mejor relación beneficio-costo en Campoalegre se obtuvo con la dosis al 50% de la fertilización recomendada sin aplicación de SAM y en Garzón se obtuvo con el testigo.

Palabras clave: fertilización, análisis económico, análisis beneficio costo, Nicotiana tabucum L.

Introduction

Among the short-term crops grown in Colombia, the cultivation of tobacco occupies eleventh place for importance by sown area (ENA, 2009). In 2009, there were 9,829 ha of Tobacco with 9,520 productive units in the country, showing an 11% increase in contrast to the year before. For the same year, the departments with the larger sown areas were: Santander (51%), Huila (17%), Bolivar (15%), Sucre (7%), with an average productive area of 1.0, 6.0, 4.0, 0.5, and 0.4 ha, respectively, and other departments such as Boyaca, Guajira, Tolima, Valle del Cauca, Cauca, Quindio, Risaralda and Magdalena (10%) (ENA, 2009).

Both bright leaf and dark leaf tobacco are cultivated in Colombia; they differ from each other by their chemical composition and organoleptic properties. Among the bright leaf variety, three types are cultivated: flue-cured (Virginia), Burley, and air-cured Virginia (Espinal et al., 2005). Flue-cured tobacco has a soft flavor and aroma, medium nicotine level and high sugar content; its combustion fumes are sweet and acidic. It is harvested leaf by leaf and cured in barns with flues conveying heat into the barns; the cured leaves acquire a yellow tone (Rojo, 2008). Burley tobacco has a neutral flavor, good combustibility and stuffing capacity; the entire plant is harvested and dried or air-cured and the cured leaves acquire a reddish coloration (Rojo, 2008). The production of bright leaf tobacco takes place in two regions that make up 81.3% of the production: The first region is composed of Santanter, Norte de Santander and Boyaca with 47.7% and the second is composed of Huila and Tolima with 37.0%. Tobacco farming is also being implemented in Quindio, Risaralda, Magdalena, Guajira and Valle del Cauca with 18.7% of the production (Espinal et al., 2005; Zambrano and Tovar, 2007).

The socioeconomic importance of tobacco farming in Colombia is based on the generation of employment due to the use of manual labor and the generation of extra income for the producing families. This crop adapts to poor soils with scarcity of water, providing reasonable economic income. It also has the advantage of a guaranteed sale and financing from purchasing companies; even though this may not often be enough to satisfy the families basic needs (CCI, 2001; Agrocadenas, 2004, 2005).

The department of Huila has been specializing in the production of flue-cured tobacco, which is cultivated mainly in the municipalities of Campoalegre, Garzon, Rivera, Altamira, Agrado, Algeciras, Palermo, Hobo, Gigante, Tesalia, Villavieja, Guadalupe, Neiva, Yaguara, Baraya, and Suaza, where Campoalegre and Garzon represent 49% of the cultivated area. This crop has played an important role in the regional economy because of the generation of direct employment and rural income, with approximately 260 daily wages/ha per crop, without taking into account indirect employment such as oil production, inputs, marketing, transport, among other. Similarly, the department receives income tax revenues and foreign exchange currency through raw tobacco exports and/or from processed products. Tobacco manufacturing generates technological advancements, employment and contributes to income generation in rural areas to the extent that it supports the production of raw material (Zambrano and Tovar, 2007).

The tobacco production system in the department of Huila is characterized by an average planting area of 7 ha in Campoalegre and 8 ha in Garzon, using mainly hired manual labor for cultivation work (temporary workers) and primarily leased plots for cultivation, having water available for irrigation, using surface irrigation, tillage practices, herbicides regularly, rotating crops such as corn, kidney beans, rice and/or sorghum and obtaining two crops a year; the first one in June-July and the second one between August-October (Plaza et al., 2011b). Within the cost structure of tobacco farming in the department of Huila, the preharvest stage is responsible for 73.5% of the costs, followed by postharvest at 20.5% and the seedbed only takes up 6.0%. Among the activities performed during the preharvest stage, fertilization is the most expensive with 26% of the costs, followed by crop set up which includes soil preparation and transplanting (Plaza et al., 2011a).

Agricultural production changes constantly and producers have to be able to use resources more efficiently to obtain a greater yield and improve quality at the lowest possible cost (Rojo, 2008). The profitability of the tobacco production system comes from the production (yield and quality) and from the costs paid by the producers related to the investment (Chouteau and Fauconier, 1993). An important task to accomplish the goal of better production and quality comes from a balanced and suitable management of the nutrients, as this will result in a healthier plant, capable of manifesting all of its genetic potential (Rojo, 2008). For the establishment of an optimal fertilization program, one that provides the amount of nutrients plants need in a timely manner to reach the production potential, one must take into account the nutritional status of the soil, the maximum nutritional absorption, the rate of absorption of nutrients during the plant's lifecycle and their distribution (leaves, stems, roots) (Moustakas and Ntzanis, 2005; Rojo, 2008).

Fertilization accounts for between 15 and 26% of tobacco production costs for the department of Huila (Garay, 2008; Plaza et al., 2011a); this percentage highlights the importance of reducing or at least maintaining said costs and improving the profitability of the crop, which is fundamental to the sustainability of the production system (Marín et al., 2008). As fertilization represents a high percentage of production costs, it is important to know the factors that influence the plant response to fertilizer applications in order to determine the proper amounts that should be applied to obtain the greatest technical and economic benefit (Flórez et al., 1978). Therefore, the objective of this paper was to provide a technical assessment of fertilization programs in the cultivation of flue-cured tobacco, in the municipalities of Campoalegre and Garzon in the department of Huila, Colombia.

Materials and methods

The study was conducted on two tobacco farms located in the department of Huila (Colombia), in the municipalities of Campoalegre (2°37.5'10'' N and 75°21.7'73'' W), located at 525 m a.s.l., with an average temperature of 28°C, relative humidity of 68% and average solar radiation of 32 MJ m^-2; and Garzon (2°13.7'76'' N and 75°36.1'66'' W), located at 790 m a.s.l., with an average temperature of 25°C, relative humidity of 74% and average solar radiation of 28 MJ m^-2. These municipalities exhibited sandy loam soils with slight and moderate acidic pHs respectively; P, K, Mg, S and Cl contents unsuitable for cultivation and an ideal texture, pH and N percentage (Tab. 1). The material used was tobacco (Nicotiana tabacum L.), Virginia variety, NC297, and the seedbed was prepared and, when the plants had 5 true leaves, they were transplanted with a planting density of 20,833 plants/ha, distributed in rows 1.2 m wide and 0.4 m between plants. Each experimental unit had an area of 57.6 m². Crop management was performed in accordance with the production practices of each study area.

The trials were established under a completely randomized design with a 3 x 2 factorial arrangement. Seven treatments and three replications per treatment were used; they corresponded to six fertilization alternatives and the conventional treatment. The conventional treatment (control) corresponded to the current treatment recommended by the Protabaco Company (Plaza et al., 2011a) and used by the producers. The alternatives (Tab. 2) corresponded to combining three fertilization doses (recommended dose, 50% of the recommended dose and 150% of the recommended dose) and two application source groups. A correct balance of nutrients when using the different fertilizer sources available for the tobacco producers was obtained by using or not using ammonium sulphate as a nitrogen source and by seeking to maintain the nitrogen ratio (NO₃ and NH₄) at 50:50. The recommendations of fertility according to soil analysis following the methodology of ICA (1992) and Gómez (2005) were considered for selecting the dosage, which correspond to 100% or recommended dose (Tab. 3). To make a recommendation on the amount of fertilizer, the levels of extraction for each mineral element were applied as reported by Ballari (2005) and an expected production of 3,200 kg ha^-1 was used.

The fertilizers used were:

17-9-18-3, containing the following elements in the proportion of N:P₂O₅:K₂O:MgO:S as 17:9:18:3:6. Ratio of ammonium and nitrate, N-NH₄:N-N0₃ = 60:40.

13:3:43, containing the following elements in the proportion of N:P₂O₅:K₂O. Ratio of N-NH₄:N-N0₃ = 5:95.

21:11:7.5, containing the following elements in the proportion of N:CaO:MgO. Ratio of N-NH₄:N-N0₃ = 50:50.

Sulfato K, containing the following elements in the proportion of K₂O:S as 50:17.

DAP, containing the following elements in the proportion of N:P₂O₅ as a 18:46. Ratio of N-NH₄:N-N0₃ = 100:0.

Fertilizer applications were conducted according to the different mineral absorption curves for the plant (Rojo, 2008), split into two applications. The first application occurred 8 days after transplantation (DAT) and the second 35 DAT for both municipalities.

Yield and quality

When the leaves had ripened, they were harvested and cured in barns heated by flues from coal furnaces. The cured leaves were then classified, taking into account parameters of physical quality such as leaf level (bottom-B, middle-M, superior-S, and Top-C), the degree of ripeness of the leaf, its color (lemon-L, orange -N, red-brown-RC, green-SG), health, body or thickness of the leaf lamina, size (length), elasticity, shine and aroma, which were then grouped into four grades (1-first, 2-second, 3-third and others) (Tab. 4); these parameters were evaluated from the Protabaco Company. Subsequently, the leaves were weighed having been grouped by quality: first (B1L + M1L + S1L), second (B2L + M2L + S2L), third (B3L + M3L) and others (all other remaining qualities); and, afterwards, the total yield for all of the grades were tallied. Since the production of the first grade quality was very low, the first and second grades were combined and analyzed as one.

Gross and net income

Gross income is the amount earned by calculating the yield (obtained per hectare) and the selling price for each grade according to leaf quality. Net income is the difference between gross income and the total of production costs per treatment. The sale price was determined according to the grades obtained for each treatment at the time of sale of the cured leaves and is given by company buyers. Protabaco Company handles up to five grades and, within each grade, there are different prices depending on class. The average percentage difference in prices between classes of the same quality varies as follows: 15% in the 1^st grade, 38% in the 2^nd and 3^rd and 46% to 51% in the 4^th grade. The 1^st grade has eight classes, the 2^nd has 11, the 3^rd has 11, and the 4^th and 5^th have 7 classes (Plaza et al., 2011a).

The criteria taken into account when choosing the optimal dose and combination of fertilizers for flue-cured tobacco were: yield, fertilization cost, gross income, net income and sale quality characteristics. Similarly, an economic analysis was conducted with the cost-benefit ratio for all treatments, which resulted from dividing gross income by total production costs.

Fertilization costs were calculated from the commercial value of the fertilizer sources (Tab. 5), the doses used and the manual labor for the treatments evaluated in each of the studied municipalities. All other factors involved in the production cost structure remained constant in each of the study areas as they shared the same crop management.

Statistical analysis

An analysis of variance (ANOVA) was conducted with the SAS statistical software v. 8.1e (SAS Institute, Cary, NC) and, when significance was found, an LSD (least significant difference) mean comparison test was conducted with a reliability of 95%.

Results and discussion

Yield

The yield did not exhibit significant statistical differences for the factors evaluated (P≤0.05). The better results in the municipality of Campoalegre were achieved without the use of ammonium sulphate (AMS) at the three application doses of b50, b100 and b150, which presented yields of 39, 32 and 33%, respectively, higher than the conventional treatment (Tab. 6). In Garzon, the treatments that reported the higher yields were achieved through the use of AMS at 100% of the dose (a100) (a dose 5% higher than the conventional treatment), at 100% of the dose without the use of AMS (b100) (a dose 6% higher than the conventional treatment) and the conventional treatment (the fertilization performed by the producers) (Tab. 6).

On the other hand, it can be appreciated that the municipality of Campoalegre showed a higher average yield of cured tobacco leaves (3,080 kg ha^-1) with regard to Garzon (2,640 kg ha^-1). These results coincide with those reported by Plaza et al. (2011a), who made a collection of yield and quality reports from raw material producers and suppliers for Protabaco in the municipalities of Campoalegre and Garzon from 2005 to 2008; finding that Campoalegre had an average yield of 2,545 kg ha^-1, 2.3% higher than the departmental average (2,486 kg ha^-1) and 6.2% higher than the Garzon average which showed a yield of 2,396 kg ha^-1, lower than the departmental average.

The reasons for the higher yield of Campoalegre include that this municipality has increased net photosynthesis, stomatal conductance and transpiration of the tobacco crop, because it has more solar radiation, a higher average temperature and lower relative humidity, as compared to Garzon (Hoyos, 2013). The growth and development of plants depends on various environmental variables, such as temperature, relative humidity, light intensity and availability of water and essential minerals (Azcón-Bietoet al., 2004; Hermans et al., 2006). These environmental factors also modify the photosynthetic capacity of the plants.

Purchase quality

Tables 7 and 8 show the production of cured leaves according to purchase quality for both municipalities studied. As for the grades that represented the highest production for each of the treatments, in Campoalegre, it was observed that the S2L grade (see characteristics in Tab. 4) showed the greatest production outcomes for the treatments with a dosage of 150% of the recommended dose (a150 and b150) with values of 26 and 33%, respectively. The S3L grade (Tab. 4) showed the highest percentages for the treatments with fertilization doses at 50% (a50 and b50), with the dose at 100% without using ammonium sulphate (b100) and with the conventional treatment with values of 45, 38, 44 and 29%, respectively (Tab. 7).

Technical and economic analysis

Considering yield, fertilization cost, gross income, net income and the production quality for sale, it was observed that, for the municipality of Campoalegre, the best results were achieved with the treatments: b50, b100 and b150, which corresponded to the recommended fertilization treatment with 17-9-18-3, 13:3:43 and 21:11:7.5 for the three application doses (50, 100 and 150%). Among the previous alternatives, b50 showed the highest yield, lowest fertilization cost, a high percentage of third quality leaves and the highest gross and net income; the alternative b100 showed a high yield, the highest percentage of third quality leaves, intermediate costs and income. The alternative b150 showed a high yield, the highest cost, the highest percentage of second quality leaves and an intermediate income. The other alternatives showed lower yield and income and greater variations in the sale quality (Tab. 9).

In Garzon, the treatments a100 and b100 and the control achieved the better results with individual differences in cost, yield and sale quality percentage. The a100 treatment, which corresponded to the application of 17-9-18-3, 13:3:43, AMS and 21:11:7.5 at 100% of the dose, showed a high yield, the highest cost, the highest percentage of second grade leaves, the highest gross income and an intermediate net income. The b100 treatment corresponded to the application of 17-9-18-3, 13:3:43 and 21:11:7.5 (100% of the dose); this alternative presented the highest yield, a high percentage of second grade leaves, and an intermediate cost and income. The control treatment, where fertilization was implemented by the tobacco producer, applying 17-9-18-3, 13:3:43, AMS and potassium sulphate, had a high yield, lower costs, a high percentage of second grade leaves, an intermediate gross income and the highest net income. The other alternatives had lower yields and showed income variations at the time of sale (Tab. 10).

The analysis of the cost-benefit ratio is useful as an economic criterion for producers as it allows them to estimate the income received for each monetary unit spent on fertilizer (Flórezet al., 1978; López, 1997). The cost-benefit ratio did not exhibit significant statistical differences for the evaluated factors (P≤0.05). The best treatment in financial terms is the one with the highest ratio of benefits to costs, which can be seen in Tab. 11. For the municipality of Campoalegre, the best treatment was without the application of ammonium sulphate, at 50% of the dose (b50), because for every monetary unit invested, a profit of 1.44 monetary units was obtained. For Garzon, the best treatment was the control, because 1.15 monetary units were obtained per each unit invested.

Conclusions

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