Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The effect of soil moisture levels in the development of Capsicum chinence Jacq plants and survival and development of Bemisia tabaci Genn was evaluated. Four treatments were evaluated, 60%, 50%, 40% and 30% soil moisture levels, which were calculated from the value of the irrigated area and the plant container area. Plant height, stem diameter, total dry biomass, substrate moisture content, water potential and water use efficiency were evaluated. To determine the effect of the plant water status on Bemisia tabaci, the number of eggs laid, egg and nymph mortality and mean time of nymph development were recorded. A direct positive correlation was found between the soil moisture and the plant water potential, the treatment with highest soil moisture provided better moisture conditions for plants. Plants treated with the higher levels of soil moisture showed significantly higher plant height, stem diameter and root volume. Higher oviposition and lower developmental time of nymphs of B. tabaci were observed on plants treated with 50% soil moisture. Eggs and nymph mortality were not affected by soil moisture levels.

This study aimed to evaluate the effect of season of the year (SY) and stocking rate (SR) on forage yield, utilization efficiency, development of plant components, crude protein (CP), cell wall content (CWC), ruminal degradation of dry matter (DM), acid detergent fiber (ADF) and neutral detergent fiber (NDF) of native grasses, in two consecutive years, in Veracruz, Mexico. Treatments included 2, 3 and 4 cows ha-1 during the rainy, windy and dry seasons. For each SR, 10 Holstein x Zebu cows were used in 10 paddocks of 0.5, 0.33 and 0.25 ha for SR 2, 3 and 4 cows ha-1, respectively. Each paddock was grazed for three days and had a rest period of 27 days. A randomized design with two replications was used. Stocking rate did not affect forage yield (6171 kg DM ha-1), CP of leaves (9.9 %) and stems (7.2 %), CWC, ruminal degradation of DM of leaves (69.8 %) and stems (70.7 %), nor NDF of leaves (69.6 %) and stems (73.5 %), whereas SY did affect these variables. The SY was the main factor affecting forage yield and nutritive quality. The density and length of stems, and the length of leaves were higher at a lower SR in the rainy season.

Grower’s previous experience and their ability to communicate technical information to other growers, allows greater adoption of technologies. Thus, appropriation of technologies of mite management and sampling was evaluated, based on the “Simultaneous Productive Growth Groups (SPGG)” technology transfer model. A preliminary diagnosis was made, evaluating the technology transfer achieved by six leading growers showing up continuously to seven meetings carried out from March to July 2010, and also by 19 growers showing up on a more irregular basis. All growers were from the municipality of Cotaxtla and belonged to the Papaya-Product-System of Veracruz, Mexico. Participation, attitude and efficacy of training were evaluated with a survey. Forty-two percent of growers considered the papaya ring spot virus as the main problem and 48 % revealed spider mites as the second one; 96 % used pesticides on spider mites. Participation of the SPGG basic group was 71 %, who agreed on sampling, recording data in sampling forms and using selective acaricides. Seventy percent were able to recognize spider mites from predatory mites and 83 % recognized selective acaricides. Growers considered that sampling can help reduce control costs. The SPGG model allowed building collective knowledge and better decision making by the working group.

Wetlands play an important role in the global carbon (C) cycle because they act as sinks of this element. Vegetation in the wetlands is a factor that influences C storage in these ecosystems. We investigated C storage in freshwater wetland soils with different types of vegetation (swamps and marshes) in the coastal plain of Veracruz, Mexico. The study sites were: Estero Dulce (ED), Tecolutla and Laguna Chica (LCH), Vega de Alatorre. Bulk densities observed ranged from 0.1 to 1.15 g cm3. Average C stored in LCH was higher in swamp (13.30±0.11 %) than in marsh soils (4.52±0.02 %). However, in ED the C content was similar in swamp (5.88±0.03 %) and marsh soils (5.28±0.02 %). In LCH marshes, there was approximately 50 % less total C in the soil compared to the C content in the swamps. In ED, the C stored in the marshes was only 7.15 % lower than the C stored in the swamps. When the total C storage of freshwater swamps (35.04±4.0 kg cm-2) and marshes (24.8±4.0 kg cm-2) was compared, there was no effect caused by the type of vegetation (P = 0.213).

Se determinó el efecto del amamantamiento y del efecto macho sobre la duración del anestro posparto en ovejas Pelibuey y sobre el peso corporal de éstas y sus crías. Siete días después del parto 56 ovejas adultas y sus crías fueron asignadas al azar a los tratamientos: T1) Amamantamiento continuo (CS; n=14); T2) Amamantamiento controlado (RS; n=14); T3) Amamantamiento continuo con carnero (CSR; n=14); y T4) Amamantamiento controlado con carnero (RSR; n=14). Un carnero con mandil fue introducido con las ovejas del día 7 al 60 posparto por 30 min dos veces al día. El peso corporal de ovejas y corderos se registró semanalmente del parto al destete. El porcentaje de ovulación en los primeros 60 días posparto fue mayor en RSR (100 %; P ≤ 0.05) que en RS, CSR y CS (57.1, 64.8 y 35.7 %, respectivamente). El control del amamantamiento redujo (P ≤ 0.05) el intervalo parto-primera ovulación (ILFO) en RSR (42.07±2.8 días) con respecto a RS, CSR y CS (51.07±3.24, 50.50±3.26 y 56.71±1.73 días, respectivamente). No hubo diferencias (P > 0.05) en peso corporal de ovejas y corderos. La interacción amamantamiento controlado-efecto macho aumentó el porcentaje de ovulación antes del día 60 posparto y redujo el ILFO, sin afectar el peso corporal de ovejas y corderos.

One of the main problems affecting cattle production in tropical regions is infestation by ectoparasites, particularly the tick Rhipicephalus (Boophilus) microplus and the horn fly Haematobia irritans. The objective of this study was to evaluate the genetic and environmental factors that influence on the resistance of grazing calves against the tick R. microplus and the fly H. irritans. The study was carried out in Veracruz, Mexico. The ticks and flies counts were made from September 2007 to March 2008, in 27 eight month-old terminal cross calves. Data were analyzed through ANOVA, with the amount of ticks and flies as the dependent variables. Tick infestation was influenced by genotype (P < 0.05), period (months; P < 0.001), temperature (P < 0.001) and rainfall (P < 0.05), but not by sex and relative humidity (P > 0.05). Fly infestation was influenced (P < 0.001) by sex, genotype, period (months), temperature and rainfall, but not by relative humidity. In conclusion, the genetic and environmental factors did influence infestation by ticks and flies in growing calves.

Scientists writing and participating in our Scientific and Technological Meeting in Agriculture, Forestry and Livestock in Veracruz during 23 consecutive years has been a challenge, due to the difficult conditions that most part-time researchers in the tropics encounter, with limited resources. Under these circumstances, providing a media for publication is just what they need to get involved in peer review publication. This special issue of Tropical and Subtropical Agroecosystems is a sample of the scientific activity going on mostly in Veracruz, but it also includes some other areas of the Mexican Tropics.

Los derrames de petróleo afectan las propiedades físicas del suelo y especialmente las poblaciones naturales de microorganismos. En particular causan disminución en bacterias fijadoras de nitrógeno de vida libre, encargadas de asimilar y reciclar nutrientes en los ciclos biogeoquímicos; al alterarse éstos, se afecta la fertilidad del suelo. El objetivo de esta investigación fue evaluar el impacto del petróleo crudo sobre bacterias fijadoras de nitrógeno de vida libre en un suelo bajo condiciones controladas. Se experimentó en suelo contaminado con cinco concentraciones de petróleo (1200, 3500, 10,000, 20,000 y 40,000 mg kg-1 en peso seco) en un diseño completamente al azar. Se midieron las poblaciones bacterias fijadoras de nitrógeno de vida libre en cada concentración. El índice del impacto microbiano de las bacterias mostró que al final de la prueba (219 h), en cada una de las cinco concentraciones de petróleo hubo un incremento exponencial de colonias bacterianas altamente significativo (P ≤ 0.01), 2 a 3.5 veces más abundantes que en el testigo. Se infiere un fenómeno de recolonización y adaptación al medio. A nivel macroscópico, en los tratamientos con mayor concentración de petróleo hubo menor diversidad de colonias, pero las poblaciones fueron significativamente mayores. También, en los tratamientos de mayor concentración del hidrocarburo, se observaron colonias bacterianas no presentes en el tratamiento testigo. Las bacterias fijadoras de nitrógeno de vida libre podrían adaptarse a condiciones adversas. La selección de las más aptas sería útil en la biorremediación o saneamiento de zonas impactadas por petróleo crudo.

The feedlot cattle producers in the south zone of the State of Mexico, generally does not an correct planning of sale to the market of yours finished hooky. Likewise, they lack a technical and administrative managing in his productive units, focused with the efficient use of inputs, which has prevented that they maximize her monetary earnings. The present research was realized to estimate the levels technical (TOL) and economic optimal (EOL) in feedlot cattle, using two cubic functions of production with diminishing marginal returns. There was in use 100 hooky Bos taurus x Bos indicus. Alive weight-LW to beginning of the fattens of 290 ± 15 kg, age 21 to 24 months fattened in feedlot during 93 days consuming a diet totally mixed (Protein: 133.33, FDN: 237.44, FDA 114.33 g/kg MS and 2.62 MS's Mcal/kg of metabolisable energy). To estimate the both functions (TOL and EOL), the profit of weight was considered to be a dependent variable. For the first production function the food consumption was taken as an independent variable and in the second the time defined in days. For the first production function the TOL was of 475.04 and the EOL was of 473.94 kg of LW; with a food consumption of 12.58 and 12.36 kg/day. For the second production function the TOL it was 475.01 and the EOL of 460.21 kg of LW, with a period of 93.29 and 77.21 days. The ideal point of sale and the maximum profit is obtained by the second production function, when the animals they come an LW of 460.21 kg during a food period of 77.21 days