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

Alternatives to reduce losses of nitrogen (N) in the soil, increasing the use of the plant nutrient efficiency are important depending on N dynamics in the soil, to increase their use and achieve high yields economically profitable. In this context, economically-analyzed whether the effect of the mechanical application of N doses as urea, in different forms and times of application, in the grain yield of corn in Cerrado region with low altitude (Brazilian Savannah). The experiment was conducted in Selvíria – state of Mato Grosso do Sul, an Oxisol clayey, in 2013/14. The experimental design was a randomized complete block design with four replications, in a factorial 6 x 2 x 2, as follows: 6 N doses (0, 50, 100, 150, 200, 250 kg ha-1), 2 application times (totally in sowing or topdressing) and 2 application forms (surface or incorporated) of N, analyzing total operacional cost (TOC), effective operacional cost (EOC), gross revenue (GR), operating profit (OP), profitability index (PI), equilibrium price (EP), and equilibrium yield (EY). The urea application at a dose of 150 kg ha-1, fully applied at sowing and surface provides greater profitability in irrigated maize, ensuring profitability with production of grains in the Cerrado with low altitude.

Mulching technology is not only easy for farmers to use but it can also reduce soil erosion and increase plant growth. This research aimed to observe the effectiveness of maize stalk mulch on runoff, erosion, sediment enrichment ratio (SER), and plant growth. The experiment was carried out on upland farming in Andisols at the beginning of the dry season (April to June 2015). Mulch treatment was undertaken on bench terraces farms with doses of 0, 4, 8, and 12 tons ha-1 on 2 types of plants (cabbage and red beans). Maize mulch application has not significantly reduced runoff and erosion. The mulch dose of 12 tons ha-1 reduced runoff and erosion by 5.1-5.2% and 25.6-26.5% compared to soil without mulch. The spread of maize stalks mulch reduced sediment concentration but increased the nutrient concentration in sediments (SER value). The application of 12 tons ha-1 of maize stalks mulch increased the cabbage fresh weight by 33.5% and the red beans dry weight by 41.4%.

Soil tillage and vegetation cover impact a great deal on hydrological processes in soil. However, there exist a dearth of literature on the extent of these effects in semi-arid Nigeria. This study investigated the effect of tillage practices (no-till, (NT) reduced till (RT) and conventional tillage (CT)) and cover crops (Centrosema pascuorum (CP), Macrotyloma uniflorum (MU), Glycine max (GM), Cucurbita maxima (CM) and no cover crop (bare) as control) on soil water infiltration rate and characteristics. A double ring infiltrometer was used to carryout infiltration study of soils under the aforementioned tillage practices and cover crops. Data obtained were used to calculate infiltration rate and these were also fitted into the Philip and Kostiakov’s models. The quality of adjustment of the models was verified by a chi square and T test, coefficient of determination (r2) and standard deviation. Result revealed higher infiltration rate in soil under conservation tillage (NT and RT) due to soil pores continuity, than in the CT where the pores had been disrupted by tillage implement. Similarly, the use of any of the evaluated cover crops improved water infiltration better than the bare soil with no cover crop. Conservation tillage system (RT and NT) favoured better soil infiltration rate by 41.25% and 29.53% respectively more than conventional tillage system. Plots with cover crops had 65.27%, 59.46%, 54.88% and 18.9% higher soil water infiltration rate in CP, MU, GM and CM treatments respectively than the bare (no cover crop) treatment. Both Kostiakov and Philip’s model were suitable for predicting the first one-minute infiltration rate. However, Kostiakov’s equation showed superior performance over Philip’s equation, in determining cumulative infiltration, this was evident from the lower standard deviation and CV values of Kostiakov’s parameters. In addition to the general non-significance differences obtained between measured and Kostiakov’s predicted infiltration values as revealed by Chi square test.

Legumes have been used for their nitrogen fixation properties; however, farmers in tropical countries they do not usually use them, because they do not appreciate visible improvement in the soil. The aim of this paper was to analyse the effect of three tropical legumes (Phaseolus vulgaris, Canavalia ensiformis and Clitoria ternatea) on growth promoting microorganisms [Free Life Nitrogen Fixers Bacteria (FLNFB), Azospirillum sp., Azotobacter sp. and Arbuscular Mycorrhizal Fungi (AMF) on the fertility of two rhizospheric soils; one for rangeland use (Ru) and the other for agricultural use (Au). The bioassays were established under a completely randomized design with three replicates per species. The evaluated soil properties were pH; Organic matter, OM; Total carbon, TC; Total nitrogen, N; Useful Phosphorus, P; Cation Exchange Capacity, CEC; and texture. In rhizospheric soil the populations of FLNFB, Azospirillum sp. and Azotobacter sp.; as well as AMF spores were estimated. The results indicate that Ph. vulgaris was the species that showed lower N fixation in Au soil, but higher P content was found in Ru. Ca. ensiformis and Cl. ternatea had higher N fixation, increased CEC, OM and TC. Clitoria ternatea favored the accumulation of OM and TC, promoting CEC, pH and the AMF population. Canavalia ensiformis was the only species to promote differentiated development of Azospirillum sp. and Azotobacter sp. in Ru, showing higher populations with this legume. Therefore, it is recommended that these data can be considered for the conservation of tropical species, both legumes and native microorganisms.

Extreme weather events in animal production are common in tropical coastal areas and have a high impact on the livelihoods of livestock keepers. The objective of the study was to analyze the threats and risks that extreme climatic events represent in the livelihood of the dual-purpose cattle raising families of the Costa Chica in the state of Guerrero. Information was recorded on the livelihood assets, farmer´s risk perception and impacts of climatic threats on 189 production units of cattle. The information was analyzed with descriptive statistics, analysis of variance, cluster and simple correspondence with the SAS® statistical package. Six types of livelihood were identified, with predominance of cattle-crops (48.7%), only cattle (15.3%) and cattle-crops-services (12.7%). For the level of assets and income, the livestock-crops-commerce livelihood had the highest average values, followed by cattle-farming and only cattle. The perception of farmer´s climatic and flood risk was high, and drought was the risk most important. The livelihoods with income from services and commerce were the least vulnerable to climate threats, since they do not depend entirely on agricultural activities; while the only cattle livelihood was the most vulnerable, due to depends on natural resources and was affected by hurricanes, floods, droughts and high temperatures.

Imports are an important component in the available supply of carcass meat, so the objective was to determine the magnitude of the effect of imports on the main economic and technological variables in the supply of poultry meat in Mexico at a regional level, during 1996 to 2016. Two models of multiple linear regression were used, the supply was the variable dependent and, the price of chicken meat, pork, feed efficiency and imports were the explanatory. The results showed that imports increased the volume of chicken meat in Mexico; without and with imports, the dynamics of production was directly and inelastically explained by its price; inverse and inelastic to the price of pork, food price and imports; direct and elastic to the feed efficiency with the effect of imports but less elastic without imports. It is concluded that with imports, the variable that explained the dynamics of poultry production in Mexico was the feed efficiency. 

Meloidogyne incognita es uno de los principales agentes biológicos que afecta la producción del tomate, actualmente se evalúan alternativas a los plaguicidas químicos, buscando compuestos para el control del nematodo. El objetivo del estudio fue evaluar la actividad nematicida del limoneno, isotiocianato de alilo, eucaliptol (2000, 1000, 500, 250, 100 y 0 ppm), β-citronelol (200, 100, 50, 25, 10, 0 ppm) y azadiractina (12000, 10000, 8000, 6000, 4000, 0 ppm), sobre J2 de M. incognita. Se realizaron muestreos en invernaderos del Estado de Morelos, donde se tomó muestra de suelo y raíces, para la obtención de los nematodos. Los bioensayos se realizaron siguiendo la metodología de Cristóbal-Alejo, en un ambiente controlado, se evaluó la actividad biológica de cinco compuestos, bajo seis tratamientos con cinco repeticiones cada uno; y como unidad experimental se usó una caja Petri con 30 juveniles (J2) de M. incognita y se agregaron 3 mL de cada concentración para ver la respuesta de la mortalidad, las evaluaciones se realizaron a las 24 horas considerando muertos a los individuos que no respondían al estímulo del alfiler entomológico, la corrección de mortalidad se realizó mediante la fórmula de Abbott y se obtuvo la concentración letal media utilizando SAS 9.0. Los resultados de la mortalidad fueron entre el 12 y 87.9 %, sin embargo; β-citronelol fue el que presentó los mayores porcentajes de mortalidad y CL50 más bajas, por lo que se puede considerar a este como una alternativa para el control del nematodo.

The objective of the research was to evaluate the antibacterial activity of five terpenoid compounds: carvacrol, limonene, linalool, α-terpinene and thymol in Gram negative bacteria (Escherichia coli, Salmonella spp and Pseudomona spp) and Gram positive (Staphylococcus aureus and Streptococcus spp). The antibacterial activity was determined by the disk diffusion method on Mueller-Hinton agar; as controls were used alcohol 70% and two antibiotics (ceftibuten and cephalexin) were used for Gram negative and positive bacteria respectively. Were made five concentrations of 0.75, 0.45, 0.15, 0.075 and 0.05 mg mL-1 for the terpenoids compounds and antibiotics. The largest inhibition zone were presented with carvacrol (5.5 mm), linalool (6 mm) and thymol (5.5 mm) in the bacteria Salmonella spp, S. aureus and E. coli respectively. The bacteria most sensitive to the terpenoids were E. coli, Salmonella spp and S. aureus while the most resistant bacteria were Pseudomona spp and Streptococcus spp. It is concluded that there is no difference in antibacterial activity among the five terpenoids compounds when exposed to Gram negative and positive bacteria, except when evaluated with S. aureus bacteria where carvacrol, limonene and linalool have an antibacterial effect similar to that of cephalexin antibiotic. 

El uso del índice de condición corporal (CC), como herramienta para el monitoreo del balance energético y las reservas corporales de las ovejas, implica establecer la relación entre la CC y el peso vivo (PV). El objetivo del estudio fue evaluar una ecuación empírica para estimar el PV en ovejas Pelibuey, no gestantes y no lactantes, la cual fue desarrollada usando un conjunto compuesto por 303 ovejas Pelibuey no lactantes y no gestantes de 2-3 años; con PV promedio de 44.71± 9.98 kg y CC de 3.18± 1.12 (PV= 22.47 + 6.90 * CC). La evaluación se realizó a través de los análisis del Model Evaluation Systems, utilizando un conjunto de datos independientes de PV (37.38±7.71 kg) y CC (2.2±1.10 unidades) obtenidos de 52 ovejas Pelibuey no gestantes y no lactantes. El análisis de regresión lineal entre valores de PV observados y predichos demostró que el intercepto no difirió de cero (0.311, P=0.91) y la pendiente no difirió de uno (0.984, P=0.83). El modelo resultó exacto, el punto (0,1) se encuentra dentro de la elipse; la F conjunta no resultó significativa (P=0.3477). La ecuación presentó una precisión media (R2 = 0.7924) y una buena exactitud (factor de corrección de sesgo, Cb=0.99). La eficiencia de modelado (MEF = 0.7911) indicó un valor relativamente alto de concordancia entre los valores observados y sus predichos. El coeficiente de correlación de concordancia entre ambos valores fue de 0.89. La RMSEP (raíz del cuadrado medio del error de predicción) represento el 9.27% del PV observado. El modelo de predicción evaluado mostró una buena precisión y exactitud para estimar el PV de ovejas Pelibuey no gestantes y no lactantes con rangos de PV de 26.3 a 75.0 kg criadas en los sistemas de producción del trópico húmedo. Además, el modelo sugiere que se requiere 6.90 ± 0.32 kg de PV para incrementar en una unidad la CC en ovejas Pelibuey de este tipo.

Successful development of YY technology depends not only in the identification of YY males (YYM), but also on the evaluation of the percentage of males obtained from them. The progeny of selected potential YYM was evaluated individually in order to determine its genetic status. In total, 12 potential YYM and 12 normal females (XX) were selected. Potential YYM were selected taking into account external color, shape of the genital papillae and size. After individual crossing, a confirmed YYM was crossed consecutively with three XX females and three XY females to further assess the variation in the percentage of males obtained. A significant deviation from the 1:1 sex ratio expected for normal males (XY) was observed for ten of the twelve potential YYM that were evaluated, confirming YY status. Variation ranking between 88 to 93% in the percentage of males was observed in crosses between YYM and XX females. Finally, failure to obtain only 100% males was observed in crosses between YYM and XY females. This variation could be the result of the interaction of minor genetic parental factors or the water temperature during fry period. External parameter used for selection of potential YYM need to be optimized in further work.