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Revista mexicana de ciencias agrícolas

versión impresa ISSN 2007-0934

Rev. Mex. Cienc. Agríc vol.8 no.7 Texcoco sep./nov. 2017

 

Research notes

Increased size and weight of onion bulb (Allium cepa L.) by nutrient translocation

Guadalupe Alfonso López Urquídez1 

Santos Antonio Gastélum González1 

Tomás Díaz Valdés1 

Felipe Ayala Tafoya1 

Jesús Ignacio Madueño Martínez1 

Carlos Alfonso López Orona1  § 

1Facultad de Agronomía-Universidad Autónoma de Sinaloa. Carretera Culiacán-El dorado km 17.5, Culiacán, Sinaloa, México. (alfonsolopezurquidez@uas.edu.mx; santos.91@hotmail.com; tdíaz10@hotmail.com; tafoya@uas.edu.mx; jesmadu-@hotmail.com).


Abstract

The onion (Allium cepa L.) is the second most important food vegetable worldwide after the tomato and generates numerous jobs. Likewise, the average yield in Sinaloa is low relative to other parts of Mexico and the world. In this research we sought to know the increase of the size and weight of the white onion bulb, from the moment of folding of the leaf until its harvest. The variety “Carta Blanca” (Nunhems) was used that is of short days. A simple random sampling was performed on a surface of three hectares. Three measurements were taken, with an interval of one week between them. Measurements started when the blade was folded. To perform the statistical analysis, the normality of the data was verified and the homogeneity test was performed. The data were submitted to analysis of variance and mean Tukey comparison (p< 0.05) with the SAS statistical package. A sensitivity analysis was also performed to estimate economic viability. The results show that at the beginning of leaf bending, the average diameter of the equatorial bulb was 7.48 cm, after one week the bulbs were 8.02 cm (difference of 0.53 cm). In the second week the difference with respect to the beginning of the folded sheet was 0.78 cm. In addition, during the third week the onion bulbs have stopped growing, at the same time the leaves lose their green color. This shows that the translocation continues even after having reached the physiological maturity of the plant which is manifested by folding the leaf. The sensitivity analysis indicates that if the onions were sold at 4 pesos and harvested one week after folding the leaf, the extra benefit would be $17 903.78 with an amount of 100 thousand plants per hectare and up to $71 615.13 with 400 thousand plants. In addition, two weeks after the doubling, the gains would be $26 363.18 and $105 452.70 respectively.

Keywords: bulbification; dormancy; folded leaf

Resumen

La cebolla (Allium cepa L.) es la segunda hortaliza alimenticia más importante a nivel mundial después del tomate y genera numerosos empleos. Asimismo, el rendimiento promedio en Sinaloa es bajo con relación a otras partes de México y del Mundo. En esta investigación se buscó conocer el incremento del tamaño y peso del bulbo de cebolla blanca, desde el momento de doblado de la hoja hasta su cosecha. Se utilizó la variedad “Carta Blanca” (Nunhems) que es de días cortos. Se realizó un muestreo aleatorio simple en una superficie de tres hectáreas. Se realizaron tres mediciones, con un intervalo de una semana entre ellas. Las mediciones iniciaron cuando se dobló la hoja. Para realizar el análisis estadístico, se verificó la normalidad de los datos y se realizó la prueba de homogeneidad. Los datos se sometieron a análisis de varianza y comparación media de Tukey (p< 0.05) con el paquete estadístico SAS. También se realizó un análisis de sensibilidad para estimar la viabilidad económica. Los resultados muestran que al inicio del doblado de la hoja, el diámetro medio del bulbo ecuatorial fue de 7.48 cm, después de una semana los bulbos fueron de 8.02 cm (diferencia de 0.53 cm). En la segunda semana la diferencia con respecto al inicio de la hoja plegada fue de 0.78 cm. Además, durante la tercera semana los bulbos de cebolla han parado el crecer, al mismo tiempo que las hojas pierden el color verde. Esto demuestra que la translocación continúa incluso después de haber alcanzado la madurez fisiológica de la planta que se manifiesta plegando la hoja. El análisis de sensibilidad indica que si las cebollas se vendieran a 4 pesos y cosecharan una semana después del doblado de la hoja, el beneficio extra sería de $17 903.78 con una cantidad de 100 mil plantas por hectárea y hasta $71 615.13 con 400 mil plantas. Además, dos semanas después del doblado, las ganancias serían de $26 363.18 y $105 452.70 respectivamente.

Palabras clave: bulbificación; doblado de la hoja; dormancia

The onion (Allium cepa) is the second most important vegetable worldwide after tomato, with approximately 85 795 190 t produced in the world, where Mexico contributes 1.48% (FAOSTAT, 2014). In Mexico 2014 were harvested 47 430.57 ha with a production of 1 368 183.69 t (SIAP, 2016). While in Sinaloa for the same year 1 480.7 ha were harvested; however, the average yield was only 23.04 t ha-1 in 2014 (SIAP, 2016).

The factors influencing the onion bulb formation are day length, temperature and variety (Lancaster et al., 1996; Brewster, 2008). Bulbification occurs when certain heat hours have accumulated (Lancaster et al., 1996). According to Tapia (1999), the onion is cold season and is moderately frost resistant. High temperatures can stress the onion plant, causing physiological disturbances, decreasing leaf development speed and number (Tesfay et al., 2011).

On the other hand, the influence of photoperiod is affected by the quality and intensity of the light, because the light infra red and high light intensities favor the development of the bulb (Bertaud, 1986). As the duration of the day decreases, the light intensity decreases, the leaves perceive it and send signals to other parts of the plant, initiating dormancy (Chope et al., 2012). According to the above, the combined effect of temperature and photoperiod induces the formation of onion bulbs, although it may be that in tropical areas temperature is a more determinant factor (Tesfay et al., 2011).

The nutrients of the onion initially pass from the soil to the plant, leading to the area where photosynthesis takes place. From there they are transported to the growing areas and to the storage regions. Palacios et al. (2005) observed that the onion began to absorb K at 52 days after transplantation.

They also found that during the 90 days after the transplant they extracted 94% of the total K; the leaves began to extract K at 38 days after transplantation and in a period of 70 days extracted 96% of their total K. From day 122 translocation to the reserve organs began; also observed that accumulation of K was initiated in the bulbs at 94 days after transplantation; In addition, the percentage of K was always higher in leaves than in bulbs (Palacios et al., 2005). Based on the above, the objective of the present work was to determine the increase in size and weight of the bulb that occurs after folding of the leaf, due to the translocation of nutrients.

The study was conducted in the autumn-winter cycle 2015-2016 in a San Lorenzo Valley in Culiacán, Sinaloa, located at 24° 27’ 27.53” north latitude, 107° 16’ 02.32” west longitude of the Greenwich meridian, and an altitude of 38 m, the climate of the region is Bs (h’), very warm semiarid with a precipitation / temperature quotient greater than 22.9 (García, 1988).

The Nunhems company’s “Carta Blanca” seed was used, this is short days with a white bulb, round shape, tolerant to flowering and maturing 170-175 days after planting. The seedling was produced in seedbeds using a polypropylene microtunnel.

The ground was prepared by subsoiling, tracking, and leveling with a plank, finally proceeding to form beds of 1.6 m wide center. In each bed six plant lines were formed with a separation of 12 cm between them. The distance between plants was also 12 cm arranged in staggered. The experiment was performed under drip irrigation conditions, using tape (T-Tape, John Deere, USA) with droppers at 20 cm separation and a cost of one liter per hour per dropper. In each bed three tapes were used.

Transplantation was started 60 days after sowing, when the seedling reached approximately 4 mm in diameter. To do this the plant was removed from the soil and pruned leaving the leaves about ten centimeters high to avoid dehydration during the transplant. Before the transplant, the econil fungicide (chlorothalonil) was applied to the seedling to prevent the attack of pathogenic microorganisms found in the soil. In addition, 295 kg h-1 of nitrogen, 100 kg h-1 of phosphorus and 110 kg h-1 of potassium were applied during the crop cycle, where the main source of nitrogen was urea fertilizer 46-00-00), phosphorus was monoammonium phosphate (12-61-00), potassium was potassium nitrate (12-00-45).

A simple random sampling was performed that was representative of a frame constituted by the number of onions planted in an area of three hectares (approximately 775 000 plants). The sampling unit was each onion. The statistical parameter to estimate the sample size was the mean and variance of the equatorial diameter of the bulb. A random sample of the population was obtained without distinguishing between its elements, in such a way that all the units had the same probability of being selected, for that the rows of onions were enumerated. At the beginning of folding of the onion leaf, the measurements of the equatorial diameter of the bulb were carried out, with an interval of one week between each one.

The normality of the data obtained for each of the tests was checked, taking into account the data of the first measurement: mean= 7.48 cm and standard deviation= 0.926, a normality check of data was made from a test of goodness of adjustment of normality using chi square (Zar, 1999). A Levene homogeneity test was also performed (Correa et al., 2006) and the analysis of variance of the differences between the means of the studied populations was performed, demonstrating that there is homogeneity between the variances. Subsequently, the data were submitted to a variance analysis and means comparison test, applying the student’s t test (Zar, 1999) with the SAS statistical package 9.0 (SAS Institute, 2002).

It was observed that at the beginning of the folding of the leaf, the average of the equatorial diameter of the bulb was of 7.48 cm, whereas a week later they had bulbs of average 8.02 cm; that is, a difference of 0.53 cm, which was statistically significant. This difference represents a percentage rate of change of 7.12. The growth of the bulb continued after the first week of measurement, so that in the second week the difference with respect to the beginning of the folding of leaves was 0.78 cm. This difference means a percentage rate of change of 10.48. Also, when comparing week 1 with respect to week 2 a difference of 0.25 cm was observed, however, it would only have a significant difference if α= 10. For the third week practically the onion bulb stopped having growth, time at which the leaf lost the green color. This makes it clear that after 15 days the onion bulb did not grow. Likewise, a correlation of 0.93 between the diameter of the onion and the weight of the onion was found (Figure 1).

Figure 1 Relationship between diameter and weight of onion bulb.  

The analysis of variance showed that there is a high significance, with a critical value of F of 7.98E-28. El análisis de varianza mostró que hay una alta significancia, con un valor crítico de F de 7.98E-28. Asimismo, el valor de la recta de la regresión fue de 84.01, es decir, que por cada centímetro que aumenta el diámetro ecuatorial de la cebolla, incrementa 84 g. Por lo anterior, las ventajas de posponer la cosecha después del doblado de las hojas son evidentes. Por lo anterior, se debe procurar que la hoja se encuentre lo más sana posible para que la mayor parte de los nutrientes que se encuentran en ella pasen al bulbo. Es decir, hay que evitar lo más posible la salida de energía de la planta hacia los consumidores, como el trips (Thrips tabaci), el gusano minador (Liriomysa trifolii) y enfermedades como el mildiú (Peronospora destructor).

In the Table 1 shows a sensitivity analysis, based on a price of four pesos (MXN) per kilogram, which shows that it may be profitable to wait a certain time to raise the onion of the land. However, it is also important to consider the probable meteorological conditions for the period when the onion would be exposed in the field, because of precipitation in that time, the product could have lower quality at the time of sale and damage the shelf life.

Table 1 Sensitivity analysis, considering estimated selling price. 

With an estimated sale price: $4.00 kg; TPV of diameter week 1: 7.12 (0.78 cm); TPV of diameter week 2: 10.48 (0.53 cm); TPV difference between week 1 and week 2: 3.14 (0.25 cm); value of the regression slope: 84 g cm-1 diameter; correlation coefficient= 0.93.

Conclusions

The onion bulb continues to grow after the leaf folds and is economically profitable to wait 15 days to start collecting the bulb. The diameter and weight of the onion continues to increase 15 days after the leaf has folded, so the producers can wait after folding the leaf, making sure that it is until it loses its green color.

It is economically feasible to postpone the onion harvest after folding the leaf. Therefore it should be ensured that during the folding period of the leaf, it maintains its green coloration as complete as possible, by controlling diseases such as mildew.

Literatura citada

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Received: July 01, 2017; Accepted: August 01, 2017

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