In Mexico, the common bean (Phaseolus vulgaris L.) is of great economic importance to the country, as it ranks second in the agri-food sector. In addition, it is a staple food in the diet of its population, mainly in low-income social strata (Rodríguez-Licea, García-Salazar, Rebollar-Rebollar, & Cruz-Contreras, 2010). This legume is important for its high content of proteins, fiber, calories, B vitamins and minerals, mainly calcium, iron, zinc, magnesium and phosphorus (Fernández-Valenciano & Sánchez-Chávez, 2017).
The deficiency of micronutrients such as iron and zinc is a public health problem that affects more than a third of the world’s population (Restrepo-Caro et al., 2016). Fe deficiency is the most important nutritional disorder in the world, since this element participates in oxidation-reduction processes, transports oxygen in enzymatic reactions linked to intracellular respiration and electron transport, catalyzes the formation of β-carotene into vitamin A, induces antibody synthesis and enhances immunity (Yin, Yuan, Liu, & Lin, 2012). Zn is ranked as the fifth highest risk factor for disease in developing countries. This element is an essential component of several enzymes (dehydrogenases, protease and peptidases); it participates in cellular respiration, in the maintenance of the cell membrane, and in the elimination of free radicals, as well as in the action of insulin in the synthesis and degradation of carbohydrates, lipids, proteins and nucleic acids (Márquez-Quiroz et al., 2018).
Unfortunately, beans come to have low Zn content when soils are deficient in microelements. Hossein, Mohammad, Hemmatollah, and Mohammad (2008) note that beans are highly susceptible to Zn deficiency, and their mobility is affected when there is an increase in soil pH, which decreases their assimilation capacity. Zn acts directly on the cellular metabolism, as a stabilizer of the structure of proteins and nucleic acids; it also keeps photosystem II active, which is important since it is responsible for capturing light during the photosynthesis process, and is part of the enzymes that participate in the perception of biotic and abiotic stress. In this way, Zn stimulates both growth and productivity (Amezcua-Romero & Lara-Flores, 2017).
Recent studies have reported that Zn application has a positive effect on grain yield and its concentration in seeds, especially in soils deficient in this element (Hidoto, Taran, Worku, & Mohammed, 2017; Shivay, Prasad, & Pal, 2014). On the other hand, Khoshgoftarmanesh, Schulin, Chaney, Daneshbakhgn, and Afyuni (2010) report that there are Zn-deficiency tolerant bean cultivars that grow and perform well in deficient soil. However, not all soils have these characteristics. Moniruzzaman, Islam, and Hassan (2008) point out that beans can absorb sulfur in large amounts, and that it is necessary to maintain the nitrogen/sulfur ratio in the plant to produce protein; sulfur application between 10 and 20 kg·ha-1 can control its deficiency.
One strategy for reducing mineral deficiency problems in plants is fertilization management, which generates micronutrient-rich staple crops. In addition, it is a relatively economic, profitable, and sustainable agricultural technique that leads to nutritionally improved crops (Beintema, Gallego-Castillo, Londoño-Hernández, Restrepo-Manjarres, & Talsma 2018). These crops are a viable means for people in the low-income stratum to obtain sufficient nutrition. Such a strategy is practical, long-lasting, and cost-effective for increasing daily mineral intake in vulnerable populations (García-Bañuelos, Sida-Arreola, & Sánchez-Chávez, 2014), which makes this approach attractive in economic terms, compared to supplementation programs. Therefore, the objective of this study was to evaluate the response in ‘Pinto Centauro’ beans to fertilization management, as well as its impact on yield, nutritional quality and profitability index.
Materials and methods
We used the ‘Pinto Centauro’ bean, which is a variety from a cross made by the National Institute of Forestry, Agricultural and Livestock Research (INIFAP) − Durango between the ‘Pinto Mestizo’ and ‘Pinto Saltillo’ beans. ‘Pinto Centauro’ is an early-cycle bean, which makes it suitable for areas with low rainfall (350 to 480 mm). This variety has a larger bean (34 to 45 g·100 seeds-1), disease resistance and a testa that is tolerant to darkening, which prolongs its shelf life and increases its market price (Rosales-Serna, Ibarra-Pérez, & Cuéllar-Robles, 2012).
The ‘Pinto Centauro’ bean crop was established during the spring-summer 2017 growing season under rainfall conditions in the municipality of Cusihuiriachi, Chihuahua, Mexico, at the “San Pedro” Ranch (28° 14’ 22.075’’ NL and 106° 50’ 1.907’’ WL, at 1997 masl). Sowing took place on July 25, 2017, and harvesting on November 8, 2017. Sowing was carried out in furrows 0.30 m high and 0.8 m wide, with a distance of 0.15 m between plants and 0.20 m between furrows. At the time of sowing, a thorough fertilization was applied. During the evaluation period, an average maximum temperature of between 34.59 and 23.41 °C, a minimum of 16.56 and 2.45 °C, and rainfall of 108.44 mm were recorded (Table 1)..
|Month||Maximum temperature (°C)||Minimum temperature (°C)||Rainfall (mm)|
Before planting, soil samples were collected at random for analysis at the Soil, Water and Foliar Analysis Laboratory of the Agro-Technological Sciences Faculty of the Autonomous University of Chihuahua (Table 2). The samples were air-dried in the shade, sieved with No. 5, 10 and 20 mesh, and stored in 1-L plastic cans. The laboratory determinations were grouped into four categories (properties) with their respective parameters. We determined soil pH (in 0.01 M CaCl2 with a potentiometer [model 410, Thermo Orion™, USA]), salinity properties (saturation percentage and pH in saturated paste), electrical conductivity (RD-B15, Beckman solubridge, USA), nitrate content (brucine and colorimetry), assimilable phosphorus (Olsen and Bray P1 [Bray & Kurtz, 1945; Olsen, Cole, Watanabe, & Dean, 1954]), potassium, magnesium (both by atomic absorption spectrophotometry) and micronutrients (Fe, Mn, Ca, Cu and Zn, in DTPA and atomic absorption spectrophotometry).
|pH (CaCl2 0.01M)||5.9|
|Electrical conductivity (ds·m-1)||0.06|
|Cation exchange capacity (mol·kg-1)||14.63|
|Organic matter (%)||0.92|
Experimental design and treatments
A randomized complete block experimental design with three fertilization treatments and four replicates was used. The treatments were: control FM1 (N, P and K, with 41, 46 and 22 kg·ha-1, respectively), fertilization FM2 (N, P, K, S and Zn, with 41, 46, 22, 12 and 1 kg·ha-1, respectively) and fertilization FM3 (N, P, K, S and Zn, with 45, 60, 22, 22 and 1.5 kg·ha-1, respectively). A single fertilization was carried out manually.
The harvest was carried out on November 8, 2017, and bean seed samples were taken from each of the treatments under physiological maturity conditions. The samples were taken to the Food and Development Research Center laboratory of the Agro-Technological Sciences Faculty for analysis.
Nutritional quality analysis
The physicochemical composition of the beans was determined in accordance with the methodology of the Association of Official Agricultural Chemists (AOAC, 2000), and in conformity with current Official Mexican Standards.
Seed weight. One hundred seeds were randomly taken from each treatment, weighed on an electronic scale (Velab™, USA) and the value recorded as g·100 seeds-1. The determination was made in triplicate.
Seed dimensions. These dimensions (length, width, and thickness) were determined with a Vernier caliper (122206, Surtek, USA). One hundred seeds were evaluated per treatment, and results were expressed in cm.
Seed color. Color parameters were measured with a Konica Minolta chroma meter (CR-400/410, Japan) (Mathias-Rettig & Ah-Hen, 2014). Measurements were made in triplicate.
Proteín. Crude protein content was determined using the Microkjeldahl total nitrogen quantification procedure. The result was expressed as a percentage.
Moisture. It was determined using the open capsule drying method. The result was expressed as a percentage.
Ash. It was determined using the methodology reported in Mexican standard NMX-F-066-S-1978. One g of sample was placed in a crucible and brought to constant weight in a muffle furnace (SNOL 1100 LHM01, SNOL, Lithuania). Two replicates were performed per treatment. Results obtained were expressed as a percentage.
Fats. The Goldfish method (NMX-F-427-1982) was used for this determination. The results were expressed as a percentage.
Fiber. Crude fiber content was determined according to Mexican standard NMX-F-90-S-1978, for which the defatted sample was used and by weight difference the percentage of fiber contained in each sample was determined.
Carbohydrates. Quantification of carbohydrates was carried out by parameter difference (calculated based on total parameters). The result was reported as a percentage.
Energy. The energy contained in each sample was measured from the sum of the calories contained in carbohydrates, fats and proteins. Values were expressed in Kcal.
Nutritional quality analysis
Sulfur. The sulfur content was determined with a FLASH 2000 analyzer (Thermo Scientific™, USA), by placing 3 µg of sample and 9 µg of vanadium pentaoxide in a nickel capsule. Analyses were performed in triplicate and the result was expressed in ppm, which was compared with the value of a known standard (Reussi-Calvo, Echeverría, & Sainz-Rozas, 2008).
Fe, Zn, Na, Mg, Mn, K, Ca, Cu and Ni. To start the analysis of these minerals, a digestion was performed using the triacid mixture method (1 L of HNO3, 100 mL of HC1O4 and 25 mL of H2SO4). The concentration of the minerals was determined by atomic absorption spectrophotometry (iCE™ 3500, Thermo Scientific™, USA). Results for micronutrients were expressed in ppm, and for macronutrients as a percent.
Phosphorus. P concentration was determined by the ammonium metavanadate (NH4VO3) method and by visible light spectrophotometry (Jenway®). Results were expressed as a percentage.
An agronomic estimate of the inputs used was made, and the cost of production and income from the sale of the product were calculated to determine the profitability of the work. The profitability ratio (benefit/cost) was calculated according to the following formula:
Data obtained were subjected to an analysis of variance and Tukey’s range test (P ≤ 0.05) using SAS Institute (2002) version 9.0 statistical software.
Results and discussion
Crop yield is the result of environment-genotype interaction and the influence of agronomic management, particularly fertilization management (Barrios-Ayala, Turrent-Fernández, Ariza-Flores, Otero-Sánchez, & Michel-Aceves, 2008). In the present study, significant differences were observed in the yield of ‘Pinto Centauro’ beans due to the effect of fertilization. The FM3 treatment had a 46.26 % higher yield than the control (Figure 1).
Yield magnitude indicates the level of efficiency of a combination of factors influencing the harvest (Amezcua-Romero & Lara-Flores, 2017). In recent studies, significant increases in crop yield have been observed with the addition of NPK + SZn, with the application of S-Zn being of great relevance in boosting bean yield (Moniruzzaman et al., 2008). The addition of S-Zn in a fertilization program has a physiological and biochemical influence on plant processes, such as enzymatic activation, chlorophyll formation, electron transport and stomatal regulation, which positively impacts the growth, development and yield of the plant (Rahman et al., 2014).
The result obtained in this study was significant, since the average bean yield under rainfed conditions in Mexico is 1,500 kg·ha-1. Jiménez-Galindo and Acosta-Gallegos (2013) obtained yields of 1,484 to 1,192 kg·ha-1, with increases of 20.8 % in the Pinto Saltillo variety; a similar trend was reported by Salinas-Ramírez, Escalante-Estrada, Rodríguez-González, and Sosa-Montes (2013). Pérez-Trujillo and Galindo-González (2003) report that it is possible to obtain yields of 2,715 kg·ha-1 in irrigated systems and of 726 kg·ha-1 in rainfed systems, which is lower than the yields obtained in this study.
Quality is the set of chemical and physical characteristics related to the nutritional value of beans (Mederos, 2006). The results obtained with fertilization management in the ‘Pinto Centauro’ bean crop in the physical variables showed a differential behavior in the three treatments tested (Table 3). FM3 showed a significant increase of 2.88 % in Hue, 20.85 % in weight and 11.59 % in length, compared to FM1. These parameters are related to quality. The increase in Hue is due to the content and distribution of pigments in the testa, which are determined by the amount of glycosides, anthocyanins and tannins. A change in the testa can be interpreted as an adaptive strategy to germinate under various environmental conditions (Tenorio-Galindo, Rodríguez-Trejo, & López-Ríos, 2008).
|Treatment||Color||100-seed weight (g)||Width (cm)||Thickness (cm)||Length (cm)|
|FM1||66.15 az||15.83 a||71.16 b||30.47 c||0.80 b||0.47 a||1.22 b|
|FM2||67.31 a||16.34 a||72.24 ab||34.54 b||0.81 b||0.49 a||1.28 b|
|FM3||67.66 a||16.69 a||73.27 a||38.54 a||0.89 a||0.51 a||1.38 a|
Seed quality is an indicator of bean conditions, since its commercial value is influenced by characteristics such as size, color and uniformity (Mederos, 2006). Bean width values were higher than those obtained by Urías-López, Álvarez-Bravo, Hernández-Fuentes, and Pérez-Barraza (2017), who report an average value of 0.74 mm. Large seeds are more accepted in the packaging industry, so producers and rural collectors prefer this type of bean and give it a higher value (Rosales-Serna et al., 2012).
The nutritional properties of beans are related to their high protein content (Ulloa, Rosas-Ulloa, Ramírez-Ramírez, & Ulloa-Rangel, 2011). The effect of fertilization management showed significant differences (P ≥ 0.05) among treatments. Results indicate that application of the FM3 treatment increased fiber content by 20.29 %, energy by 1.5 % and protein content by 8.35 % compared to FM1 (Table 4).
|Treatment||Physical-chemical parameters (%)||Energy (Kcal)|
|FM1||4.70 az||1.05 c||11.16 c||2.67 b||59.34 a||17.87 c||324.62 b|
|FM2||4.80 a||1.22 b||11.84 b||3.31 a||60.65 a||18.36 b||326.62 b|
|FM3||4.92 a||1.28 a||12.14 a||3.35 a||61.13 a||19.50 a||329.48 a|
Velasco-González, San Martín-Martínez, Aguilar-Méndez, Pajarito-Ravelero, and Mora-Escobedo (2013) evaluated the physicochemical properties of ‘Villa’ bean in the INIFAP-Durango experimental field, and obtained an ash value of 4.63 %, which is lower than those obtained in this work. This is probably due to the different varieties and environmental conditions.
Barrios-Gómez and López-Castañeda (2007) note that moisture prevents the bean from becoming brittle and losing quality. In this sense, the FM3 treatment significantly increased (P ≥ 0.05) the percentage of moisture compared to the control. Odedeji and Oyelke (2011) report fiber values ranging from 0.65 to 5.10 %, the range in which the values obtained in this study are found (Table 4). As for carbohydrates, it can be seen that the values obtained in this work are higher than those found by Fernández-Valenciano and Sánchez-Chávez (2017), with an average value of 39.02 %. Mollinedo-Patzi and Benavides-Calderón (2014) indicate that carbohydrates are a fundamental part of the diet, and in this study the energy obtained is within the required intake values.
Mederos (2006) points out that the increased protein in beans, due to fertilization management, is related to the ability of Zn to form proteins, so this mechanism is affected by the deficiency of this element in plants. Ulloa et al. (2001) indicate that, depending on the type of bean, the protein content ranges from 14 to 33 % under normal irrigation conditions. Salinas-Ramírez et al. (2013) obtained similar protein values (18.90 %) under rainfed conditions. The nutritional quality of the bean is mainly valued for its protein content, since beans are one of the main sources of protein in the diet, which is relevant in Mexico because there is a high level of malnutrition (Sangerman-Jarquín, Acosta-Gallego, Schwenstesius-de Rindermann, Damián-Huato, & Larqué-Saavedra, 2010).
Microelements such as Zn are essential for optimal plant growth. The results obtained for macro and micronutrients were significant (P ≥ 0.05) (Table 5). With the FM3 treatment, the beans showed an increase of 74 % in phosphorus, 9.45 % in magnesium, 16.30 % in iron and 39.77 % in Zn, compared to the control.
|Treatment||Macronutrients (%)||Micronutrients (ppm)|
|FM1||2.29 az||0.074 c||1.55 b||0.173 b||0.211 a||3.96 a||2.31 a||20.24 a||72.78 b||20.47 c||21.34 b|
|FM2||2.52 a||0.177 b||1.67 b||0.173 b||0.274 a||4.41 a||2.58 a||21.77 a||78.32 ab||28.97 b||22.82 b|
|FM3||2.59 a||0.289 a||1.73 a||0.183 a||0.299 a||4.77 a||2.74 a||22.10 a||86.96 a||33.99 a||23.88 a|
Beans obtained with the FM3 treatment showed significant statistical differences in Zn concentration compared to the other treatments. However, the values obtained were slightly lower (from 20.47 to 33.99 ppm) than those reported by Celmeli et al. (2018), who conducted a study in Turkey with 10 local varieties (obtaining values from 17.81 to 37.90 mg·kg-1) and some varieties from international companies (obtaining values from 25.03 to 35.1 mg·kg-1) under controlled greenhouse conditions. It is important to consider that the data in this work were obtained under rainfed conditions, and that the soil had a Zn content lower than 1 ppm. Another factor that may have influenced the results is the soil pH, since it was acidic and that hinders Zn assimilation.
Cakmak and Kutman (2017) note that Zn concentrations in the bean should be between 20 and 35 mg·kg-1, with an average value of 28 to 30 mg·kg-1. When beans are grown in Zn-deficient soils, concentrations of this element in the bean are <10 mg·kg-1. However, when the soil is rich in Zn, or is fertilized with Zn, the concentrations of this element in the bean are 20 mg·kg-1. Therefore, the results obtained in this study, considering that it is a rainfed crop, show an effect of fertilization management.
Estrada-Domínguez, Márquez-Quiroz, de la Cruz-Lázaro, Osorio-Osorio, and Sánchez-Chávez (2018) state that 61 mg·kg-1 are established as a critical level of Zn in plants to make it sufficient in human nutrition. The required Zn intake in the human diet is 11 mg per day, and cooked beans provide only 1.4 mg (Rodríguez-Castillo & Fernández-Rojas, 2003). This nutrient is essential in more than 300 enzymes, which are involved in all important biochemical reactions in the human body. Zn has a direct effect on growth, neurological development, behavior, and the immune system (López-de Romaña, Castillo, & Diazgranados, 2010).
The FM3 treatment resulted in an increase in phosphorus and iron content in the bean, reaching an average iron value of 89.99 ppm; this value is five times higher than the value of 50 ppm reported by Tofiño-Rivera, Pastrana-Vargas, Melo-Ríos, Beebe, and Tofiño-Rivera (2016). Some biofortification studies have been carried out to increase the iron content in bean, since it provides about 40 % of the iron in the diet of people who base their diet on this legume. However, it is estimated that only 20 % of the total iron present in the bean is assimilated, so its contribution is low, and if the iron content of the bean is poor, assimilation will be even lower (Mederos, 2006). García-Alanís et al. (2019) note that a person requires 8 mg of iron per day, and cooked beans provide only 1.36 mg·100 g-1. Some studies indicate that bioavailability is associated with iron content, suggesting that there is no simultaneous increase in substances that interfere with absorption, and that providing a higher iron concentration in bean varieties is an effective strategy (Welch, House, Beebe, & Cheng, 2000).
The results obtained in the economic study, which determined the profitability of applying fertilization in a ‘Pinto Centauro’ bean crop, reveal that the best treatment was FM3, since it had a higher production value (profit) and a b/c yield of 4.6, improving the gross profit by 55 % (Table 6).
|Production costs ($ MXN)||5,546.00||5,683.00||5,683.00|
|Cost of money (4.5 %)*||237.33||256.27||256.27|
|Production value ($15.00 MXN·kg-1)||18,000.00||26,355.00||33,495.00|
|Net profit ($ MXN)||12,216.17||20,415.73||27,555.72|
The above results indicate a favorable response to fertilization management in ‘Pinto Centauro’ beans in the agricultural fields of the Chihuahua region, Mexico. Ugalde-Acosta, Tosquy-Valle, López-Salinas, and Francisco-Nicolás (2011) carried out irrigation and mineral fertilization in beans, and obtained a b/c ratio of 1.80, with a gain of 20 cents per peso invested. In this study, the FM3 treatment allowed increasing the profit for the producer and recovering the investment cost.
Fertilization management is a feasible alternative that can be used to increase the productivity of ‘Pinto Centauro’ beans in rainfed soils. The results suggest that fertilization management with FM3 treatment, in addition to increasing the nutritional content of the bean, is an alternative with higher income for the farmer, since it obtains higher yields and better quality beans.
Fertilization management with the FM3 treatment increased yield by 46.26 % compared to the control; in addition, protein increased by 8.35 %, phosphorus by 74 %, iron by 16.3 % and zinc by 39.77 %.
The profitability index showed an increase of 4.6 %, with an improvement in quality and profit. Therefore, fertilization management can be a viable alternative to improve rainfed bean cultivation conditions in semi-arid regions of Mexico and the world, resulting in an increase in bean yield and nutritional value.