The enthalpy and the comfort zone in tomato production
La entalpía y la zona de confort en la producción de jitomate
Martín J. Montero-Martínez;
Irineo Lorenzo López-Cruz
Available online: 2010-12-15 / pages 53-59
Due to the lack of information about energy consumption in heating and cooling requirements ingreenhouses, the enthalpy was used as an approach of the energy content in the environment. A sensitivity analysis was done through seven Neural Network models for enthalpy prediction. It was found that the most important variables to explain the energy content in the greenhouse are temperature, transpiration, and heating and cooling systems, which correspond to inputs of model 4 with a MSE equal to 0.38 and 1.28 for one and two times ahead, respectively. Temperature and relative humidity data were collected from Santa Rosa, Sinaloa, from 1999 to 2009. The ellipses for the comfort zone were constructed in order to determine how far the external conditions are comparable with the optimal conditions for tomato production, and also to estimate the amount of energy required in each case to reach the comfort zone. Data analysis showed that most of the time those external conditions are below and right from the comfort zone, which pointed out a problem of high temperature and low relative humidity. Besides, the most critical months for tomato production are from July to September because the external conditions are far away from comfort zone, Therefore, it is recommended to dedicated those months for cleaning the greenhouse.
Cooling time of seeded mexican lime fruit, using forced air and commercial packing
Tiempo de enfriamiento en limones mexicanos, usando aire forzado y envases comerciales
Carlos Javier Martínez-Hernandez;
Available online: 2010-12-15 / pages 61-67
The fruits and vegetables commercialization process is now more demanding in guarantee of food safety and quality conservation, so the use of cold chain in developing countries like Mexico is increasing, mainly for perishable products destined to supermarkets and the international market. Pre-cooling time has cost implications and organizing shipments to buyers. The aim of this study was to evaluate the cooling time t1/2 (Z) and t7/8 (3Z), and the loss weight rate in the pre-cooling process of fruits of seeded Mexican lime (Citrus aurantifolia Swingle). It was used a cold room at 9 ± 0.3 °C, relative humidity between 90-95 %, and a pre-cooled tunnel with speed air from 1 to 2.5 m•s 1. The fruit size ranged between 33 and 45 mm in diameter, and packaging systems were commercial packing cardboard box, wooden box, polypropylene woven bag and plastic box. The results show that speed air, packing material used, and the fruit size influenced the rate of weight loss in fruits and the cooling times Z.
Design, construction, and evaluation of a husking machine to permit the use of the husks as wrapping for tamales
Diseño, construcción y evaluación de una máquina para deshojar la mazorca de maíz para envoltura de tamal
Federico F. Hahn-Schlam
Available online: 2010-12-15 / pages 69-74
The present research was developed to mechanize the process of corn husking that would permit the husks to be used as wrapping for tamales or for their use in the making of handicrafts. After determining the physical-mechanical properties of the ears of corn, a conceptual design and the details of the machine were made. The prototype was then constructed and evaluated. The technological process consisted of two principle activities: cutting off the butt of the ear of corn and husking the remains. The cut is made with a smooth blade, while the husking takes place as a result of friction between the surface of the ear of corn and the rollers that turned in the opposite direction and at a different speed. The corncob is expulsed to the side because of the movement of the rollers and the husk that goes between these. The productivity of the machine is 790 ears of corn•h 1 at a feeding speed of 0.03 m•s 1. Tests showed husking at 95 %, mechanical damage to the husks at 1.4 % and up to 11 % of the husked corn had husks with a humidity of 50.4 %. The dependence of the energy of court depending on the diameter of the ear was determined. An evaluation of the amount of electricity used in the case of a smooth blade as compared to a toothed one determined that the latter requires 6.5 % more electricity.
Treatment options for wastewater of three swine farms
Productividad del agua en el cultivo de maíz en condiciones del sur de La Habana
Available online: 2010-12-15 / pages 81-86
The high level at which water affects agricultural production and its capability of the latter to feed populations leads to the need of studying the problem of water productivity. The study of the crop water production function and its application in planning water use is an important strategy to increase water productivity. Data of 12 experiments carried out at the Irrigation and Draining Research Station, located in Alquizar at south of Havana Province (red ferralitic soils), and regression tools were used to estimate the crop water productivity (WP) and crop yield response factor (Ky) for corn. Crop water productivity based on evapotranspiration (WPET) ranges between 0.9 and 2.5 kg•m-3, while the WPI was 16.43 kg•m-3 when 266.8 m3•ha-1 of irrigation water were applied. The range 0.86 to 2.9 kg•m-3 of WPT obtained for corn was in a wider range than the that reported by FAO for this crop. Every cubic meter of total water used in corn yield 1.93 kg. The slope (Ky) of the corn water productivity function was 1.67 in winter and 2.31 in summer. The relative loss of yield was proportional to irrigation deficit in both seasons. For a planned irrigation deficit of 20 % for corn it will expect a relative loss of 33.4 and 46.2 % of yield, in winter and summer respectively.
Treatment options for wastewater of three swine farms
Opciones de tratamiento para aguas residuales de tres granjas porcícolas
Violeta Eréndira Escalante-Estrada;
Available online: 2010-12-15 / pages 87-90
For the treatment of wastewater there are low-cost technologies such as stabilization ponds and anaerobic processes. Both technologies have been used to treat high load wastewater such as swine farm wastewater. The aim of this paper was to present treatment options for different types of swine wastewater, conducting an analysis of area requirements. We present the characterization of wastewater from three different swine farms (technified, low sophisticated and backyard) is presented, besides a description of the treatment system for each case, calibration of the design for the backyard farm. The proposed treatment configurations allow reducing 31 % the area requirements (m2•m 3), for the low sophisticated farm by including an anaerobic digester; and 35 % in the area requirements (m2•m 3) for the technified farm by including an anaerobic digester and an upflow anaerobic reactor in the treatment train.