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

La agricultura (incluyendo ganadería) es considerada como una de las principales fuentes de gases efecto invernadero. Por lo cual, el monitoreo de los gases efecto invernadero (GEI) en dicha actividad es necesario para lo cual existen diversas metodologías. La técnica de covarianza de vórtices es una de ellas permitiendo el análisis de GEI de manera continua. Acuerdo con esto, se planteó la instalación y evaluación de un sistema GHG-2 para el monitoreo de CH4 y CO2 en un hato lechero en un sistema semi-estabulado en Sonora. Los resultados muestraron que el GHG-2 permite evaluar el comportamiento continuo de los flujos CH4 y CO2 observándose picos de ambos gases cuando el ganado estuvo presente. Asimismo, permitió corroborar la existencia de una alta correlación relación entre ambos GEI (CH4:CO2), similares a estudios previos, lo que permite utilizar esta razón para estimar las emisiones de metano en forma indirecta a través de balances energéticos para calcular CO2. Una de las limitaciones de esta técnica en sistemas conf inados o semiconf inados es la presencia de material particulado en la atmósfera que obliga a una supervisión y mantenimiento frecuente; así como el alto consumo de energía, lo cual obliga a considerar en el proyecto un adecuado suministro de fluido eléctrico mediante paneles solares y acumuladores, si no se cuenta con una fuente continua de electricidad.

The objective of this study was to evaluate nutrient consumption and exports in agricultural systems of Latin America and the Caribbean (ALC) in order to estimate the balance of the main macronutrients (N, P and K) used by crops. The nutrient balance was estimated by considering the amount of nutrients entering the agricultural systems via fertilization and biological N2 f ixation (BNF) and the amount of nutrients leaving the systems through crop harvest removal in each country. Based on off icial statistics for the year 2016, the ALC region presented a positive balance of nitrogen. However, some countries (Argentina, Bolivia and Paraguay) had a negative balance of N. Biological N2 f ixation is the main source of N in Latin American agriculture, accounting for more than 62% (11.29 Mt N) of the total N (18.10 Mt N) entering the agricultural systems. Broadly speaking, the supply of P via fertilizer in Latin America counterbalanced the removal through crop harvest, with the exception of Argentina, Bolivia, Guatemala and México, which have crop production dependent on soil P mining. Potassium was one of the nutrients whose application does not meet the demand of the region’s crops, presenting negative balances in almost all countries except Brazil, Colombia and Venezuela. Nevertheless, it should be noted that many agricultural soils from this region have naturally high K availability. Greater care in the use of inputs, including fertilizers, occurs with cropping soybean, corn, coffee, sugarcane and oranges, while the rest are dependent on natural soil fertility, which may compromise food safety.

Application of nitrogen (N) to garlic crops has been the subject of several investigations with different cultivars, growing conditions and variable response in the yield. However, the study on phenology, intercepted radiation, agronomic variables, yield and agronomic eff iciency of N are limited, and this was the objective of the present work. The research was conducted during autumn-winter 2016-2017 in the experimental f ield of the Colegio de Postgraduados, campus Montecillo, Texcoco, State of Mexico, Mexico (19° 29’ N and 98° 53’ W and 2250 m of altitude), with a temperate climate and clay-silty soil under irrigation. Sowing of the native cultivar “Pata de mula” was on October 24, 2016 and harvest was 150 days after planting. The sowing pattern (topological arrangement) was 15 × 15 cm. The treatments consisted of the application of 0, 100, 200, 300 kg N ha-1. The experimental design was random blocks with four replications. Results indicate that nitrogen supply did not affect the days to occurrence of phenological phases but caused an increase in the intercepted radiation, number of cloves, bulb size, and plant and bulb weight. Distribution of dry matter in the plant and harvest index were not affected by the application of N. The highest bulb yield was obtained with N200 and N300.  It was considered that 200 kg N ha‑1 is the optimum dose for the crop in this region with which the highest agronomic eff iciency of nitrogen is obtained.

La estimación de las áreas de influencia (footprints) de las mediciones de flujos de energía, y materia, con sistemas de covarianza de vórtices permite hacer interoperables las mediciones para analizar los problemas de cierres de balance de energía. Por un lado, las mediciones de los flujos de calor latente y sensible son dependientes de la altura de los sensores, velocidad y dirección del viento, rasgos morfo-estructurales de la vegetación y condiciones de estabilidad de la atmósfera; mientras que, por otra parte, las mediciones de radiación neta y flujos de calor del suelo no son dependientes de la intensidad y dirección del viento o de otro rasgo, solo dependen de la altura del sensor (radiación neta) o la configuración espacial de las placas de calor (flujo de calor del suelo). Para poder hacer interoperables las mediciones de radiación neta con las de los flujos de calor latente y sensible, en este trabajo se desarrollo un modelo aproximado del footprint de este tipo de sensores estáticos, el cual es parametrizado en forma simple en función de la altura del sensor y la geometría de visión y de iluminación solar. Los desarrollos permiten el uso del modelo de footprint en forma operativa, permitiendo así tener una perspectiva en relación con el problema de cierres de los balances de energía si es producto de las diferencias en los footprints de los sensores o de advección del viento.

Phytochemicals or phenolic compounds are important natural bioactive molecules that plants accumulate in response to environmental conditions and may exert benef icial effects on health by protecting humans against many diseases. The aim of this work was to analyze the influence of biotic and abiotic stress on the accumulation of flavonoids and phenolic acids on leaves of two cultivars of Amaranthus hypochondriacus, which are differentiated by the colour of their leaves (red or green). Phenolic compounds were extracted using the accelerated solvent extraction (ASE) method and their identif ication was carried out by LC-MS analysis. Rutin was the main flavonoid in amaranth leaves; the highest concentrations were found in green leaves when plants were subjected to stress (9715 μg g-1). Phenolic acids were minor compounds; ferulic acid was only present in red leaves (0.5 μg g-1) and p-coumaric acid only in green leaves (0.7 μg g-1). Our results indicate that leaves from A. hypochondriacus, the main species that produce edible seeds, are a good source of phytochemical compounds and their accumulation could be driven by the growing conditions.

Oil and gas industry produces wastewater (produced water), which contains hydrocarbons, heavy metals, and other components, such as mineral salts essential for plant nutrition. Hydrocarbons presence on produced water limits its potential use in the agriculture, as its lead to inhibition of plant growth. The present study aimed to investigate the effect of hydrocarbons analogous contained in the produced water on 1) pH and electrical conductivity (EC) of irrigation leachate, 2) plant´s morphological variables, 3) mineral concentration, 4) fruit pH, EC and total dissolved solids (TDS), during flowering and fruiting stages in tomato grown into greenhouse conditions. As source of produced water were used diesel at concentrations of 20 and 25 mg L‑1, gasoline at 40, 50 and 60 mg L-1, and benzene at 75 mg L-1, applied in the substrate by means of a syringe. All plants treated with hydrocarbons reached the fruit setting and ripening stage at the 6-cluster. Depending on their type, concentration, and exposure time, hydrocarbons modif ied the pH and EC of the irrigation leachate, caused signif icant morphological changes with longer exposure time, and restricted the biomass production. Mineral concentration differed signif icantly among plant organs, affecting mainly the sodium uptake in stems and fruits. The variables of fruit quality, EC and TDS were favorably modif ied by most treatments.

Gas exchange measurements were taken with an infrared gas analyzer (IRGA) and chlorophyll fluorescence with a modulated amplitude pulse fluorimeter (Mini-PAM) on fully developed leaves of ramon (Brosimum alicastrum Swartz) a tropical rainforest tree, grown in its natural habitat as to collect basic information of its physiological behavior. Data showed that maximum f ixation of CO2 was 5 µmol  m-2 s-1, photosynthetic eff iciency was 0.67 while the photosystem II was found to saturate at a photonic flux density (PFD) of 500 µmol at 15 h. A high correlation was found between photosynthesis and transpiration. Highest water use eff iciency occurred after 15 hours at a temperature of 30 °C, while chlorophyll levels remained constant. This is a shade tolerant, plant species thus it was found that initiates the photosynthetic process with low levels of light, presenting a light compensation point of 24 µmol m-2 s-1. In a parallel study, the same variables were measured in two sets of individuals of the same specie collected from two distant localities but growth in pots in the open. Photosynthetic variables of this plant species data showed very similar patterns. The results obtained suggest that, during the daylight hours and at higher temperatures, this species can carry out photosynthesis with high water use eff iciency. Based on the results, the conclusion is that this plant species can adapt to a diversity of environmental conditions.

Balanced and timely nutrition is important to ensure the yield and quality of avocado (Persea americana Mill.) fruit. This research was carried out in the cv. Méndez with the objectives of a) to describe the dynamics of fruit growth and the process of dry matter accumulation in mesocarp, b) to quantify the concentration and accumulation of nutrients in the mesocarp (pulp) during fruit development. In a commercial orchard with site-specif ic fertilization, 20 trees were selected and 30 summer flowering inflorescences per production cycle (2014-15, 2015-16 and 2016-17) were marked in each one. Five fruits per tree were randomly collected in f ive stages of development, from olive size to harvest, and the dry matter of the mesocarp and the concentrations of N, P, K, Ca, Mg, S, Fe, Cu, Mn, Zn and B in this tissue were quantif ied. The fruit required 300 days from anthesis to harvest. It showed accelerated growth in the f irst three stages of development (S-Olive, S-I and S-II) and lower growth in the last stage (S-III). Dry matter accumulation was constant during fruit development, although the largest accumulation occurred in S-III. In general, the concentration of nutrients in the mesocarp decreased with fruit development and its accumulation increased. The greatest fruit growth occurred in the f irst 185 post-anthesis days, when the mesocarp accumulated less than one-third of the total nutrients required until harvest. The results indicate the need to review how nutrients are supplied to the tree, to make sure they are adequately provided during fruit development.

The scarcity of pure and unrelated maize inbred lines that possess high combining ability in Mexico has led breeders wishing to form single crosses to develop double-cross or three-way line hybrids (TWLHs) instead. However, some of the farmers who grow these hybrids cultivate their advanced generations later on.  Although the resulting populations can be viewed as the synthetics that the random mating of the parental lines (SynL) of these hybrids would produce, there may be differences. The synthetic variety whose parents are t TWLHs (SynT) is interesting because the contributed gene frequencies of the three lines that are parents of a TWLH are not balanced and this may generate a difference between the inbreeding coeff icients (ICs) of the SynL and SynT. Since an unbiased and general inbreeding coeff icient of the SynT and a prediction formula for the SynT genotypic mean (GM) are not yet known, the objective of this study was to derive formulae for these two important parameters of SynT. To form the t TWLHs, it was assumed that 3t unrelated lines whose IC was F (0 ≤ F ≤ 1) were used. Unbiased and general formulae for FSynT and GM were derived for the f irst time. In particular, it was found that FSynT = [3(1 + F)]/(16t). Since the inbreeding coeff icient of the SynL derived from the same 3t lines is (1 + F)/(6t), then FSynT > FSynL. These f indings suggest that the genotypic mean of the SynL grain yield is larger than the SynT’s.