Summary (Es)

In order to determine the potential use of the infrared thermometers to estimate the crop water stress index (CWSI) instead of another techniques which are more time and labor consuming, two models of CWSI were evaluated in six lines of corn (Zea mays L.). The two models gave a good agreement between the value of the index and the magnitude of the crop water stress (R sup2 varied from 0.79 to 0.86), so it is possible to estimate the soil moisture availability by measuring the difference between the canopy and the air temperature. An inverse relation between crop yield and the value of the CWSI for each line was also found (average R sup2 =0.60) | Con objeto de determinar la utilidad potencial de la termometria infrarroja para estimar el indice de tension de agua del cultivo (Crop Water Stress Index, CWSI) en sustitucion de tecnicas mas laboriosas y tardadas, se evaluaron dos modelos del CWSI en seis lineas de maiz (Zea mays L.). Los dos modelos presentaron aceptable relacion con el grado de deficit de agua del cultivo (R sup2 entre 0.79 y 0.86) lo que permite estimar el estado actual de la humedad disponible en el suelo mediante observaciones de la diferencia de temperaturas entre el follaje del cultivo y el aire. Ademas, el rendimiento de grano y el CSWI mostraron una relacion inversamente proporcional en las seis lineas (R sup2 promedio= 0.60)

O cultivo da soca de arroz (Oryza sativa L.) pode se constituir em uma fonte de renda importante se o manejo da água de irrigação for adequado. O objetivo deste estudo foi determinar os efeitos de períodos de drenagem e de irrigação, antes e depois, respectivamente, da colheita da cultura principal sobre o comportamento da cultura principal e da soca de arroz. Os tratamentos consistiram da combinação de quatro períodos de drenagem (corte da irrigação e abertura dos drenos aos 0, 10, 20 e 30 dias) antes da colheita da cultura principal, com o reinício da irrigação aos 0, 10, 20 e 30 dias após a colheita da cultura principal, em arranjo fatorial 4x4, no delineamento experimental de blocos ao acaso, com quatro repetições. Os períodos de irrigação após a colheita afetaram diferentemente o comportamento da soca de arroz de acordo com as condições climáticas. Com temperaturas do ar mais baixas, o atraso no reinício da irrigação reduziu a produtividade e a qualidade do produto colhido. Em condições climáticas de temperaturas do ar mais altas, a inundação iniciada nove dias após a colheita da cultura principal resultou em melhor desempenho da soca, com uma economia de água de 14% em relação à inundação imediatamente após a colheita. A soca aparentemente não se apresenta favorável ao desenvolvimento de populações daninhas de larvas da bicheira-da-raiz do arroz, Oryzophagus oryzae. | The cultivation of flooded rice (Oryza sativa L.) ratoon crop may constitute a profitable activity, if an adequate water management is adapted. The objective of this study was to determine the effects of drainage and irrigation periods, before and after, respectively, main crop harvest on the performance of flooded rice main and ratoon crop. Treatments consisted of the combination of four drainage periods (0, 10, 20, and 30 days) before the main crop harvest with the introduction of irrigation at 0, 10, 20, and 30 days after the main crop harvest. The experimental design was a randomized complete block in a 4x4 factorial scheme, with four replication. The rice ratoon crop performance was differently affected by the irrigation periods after main crop harvest according to environmental conditions. Retardation in flooding decreased grain yield and grain quality, when air temperatures unsuitable to ratoon crop development occurred. Under suitable air temperatures conditions, starting flooding at nine days after the main crop harvest was the best treatment to the performance of ratoon crop, which represented 14% of saved irrigation water. Rice ratoon crop apparently is not favorable to the development of Oryzophagus oryzae harmful population.

The water yield component of the SWRRB model was validated in a watershed of 125 ha, permanent stream flow, 35 percentage of steep gradient, sandy loam soils, seasonal rainfall and grassland vegetation, in Macapo, Cojedes State, Venezuela. Water yield was measured with a Stevens water level recorder installed in a gauge channel, and compared to the predicted water yield by the model. Using directs inputs, the model underestimated water yield (with relative differences between -100 and +800 percentage). In almost all cases, as well as rainy days, surface runoff was ignored. Base flow was ignored by the model. Subsurface runoff was the more important flow in terms of model perfomance. Flows behavior can be caused by the underestimation of the CN at the high values of retention constants. Using indirect inputs, it was obtained a higher, but more variable, water yield. Water yield was found very sensitive to Curve Number, Saturated Hydraulic Conductivity and Available Water Content, this shows the involved risk in the application of the model when estimated inputs are used. SWRRB must not be used for detailed planning and design in small watershed, but it may be useful to evaluate watershed degradation and response trends in terms of land use and management changes.

Se estudió la intensidad de liberación de los conidios de C. musae producida por las gotas de agua que escurren sobre las manchas de sigatoka y por diferentes velocidades del viento. Se observó que aun a velocidades del viento muy superiores a las normalmente registradas en las plantaciones, la liberación de los conidios fue ligera o nula, mientras que el paso de una o dos gotas de agua sobre la superficie de las manchas liberó la totalidad de las mismas. Debido a las poco frecuentes capturas de conidios de Cercospora musae en las trampas de esporas se deduce que el transporte de los conidios ocurre fundamentalmente en sentido vertical, mediante el rocío y el agua de lluvia y que éstos no juegan un papel preponderante en la distribución de la enfermedad a grandes distancias, no así en el aumento de la infestación existente en las plantaciones. | The conidial release of Cercospora musae under different speeds of winds and the flowing water over the spots were studied. A little or none release even under higher wind's speeds than the usually occurs on banana plantations was observed, where as one or two small drops of water flowing gently over the surfaces of spots remove all the spores presents on them. Since, very seldom is trapped conidia on the sporetraps is assumed that the transport of them is mainly vertical and that they have a little significance on spread of disease to long distance from the source of inoculum.

Con el objeto de evaluar los índices de erosividad EI 30, KE 1 y AIm, se estableció una parcela sin cobertura de 10 m x 2 m, en un Aquic Paleumult con 15% de pendiente , ubicado en una Cuenca Alta de la Cordillera Central de Venezuela. Después de cada evento lluvioso, se midieron los volúmenes de agua de escorrentía generados y las perdidas de suelo ocasionadas. En un pluviógrafo de sifón de registro diario se colecto la información lámina-intensidad correspondiente. Se utilizó la relación energía-intensidad reportada por Wischmeier para el computo de los índices EI30 y KE 1. Mediante análisis de regresión real simple se obtuvieron con respecto a las perdidas de suelo coeficientes de determinación de 0,65, 0,69 y 0,63 y con respecto a las perdidas de agua de 0,56, 0,44 y 0,56 para EI30 ' KE 1 y AIm, respectivamente. Los tres índices se corre1acionan altamente con las perdidas de suelo y en menor proporción con 1as perdidas de agua por escorrentía. Se recomienda utilizar e1 EI30 por ser este índice el mas reportado en la literatura, asi como continuar este tipo de investigación por un numero mayor de años

Monthly time series, from 2001 to 2016, of the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI) from MOD13Q1 products were analyzed with Seasonal Trend Analysis (STA), assessing seasonal and long-term changes in the mangrove canopy of the Teacapan-Agua Brava lagoon system, the largest mangrove ecosystem in the Mexican Pacific coast. Profiles from both vegetation indices described similar phenological trends, but the EVI was more sensitive in detecting intra-annual changes. We identified a seasonal cycle dominated by Laguncularia racemosa and Rhizophora mangle mixed patches, with the more closed canopy occurring in the early autumn, and the maximum opening in the dry season. Mangrove patches dominated by Avicennia germinans displayed seasonal peaks in the winter. Curves fitted for the seasonal vegetation indices were better correlated with accumulated precipitation and solar radiation among the assessed climate variables (Pearson’s correlation coefficients, estimated for most of the variables, were r ≥ 0.58 p < 0.0001), driving seasonality for tidal basins with mangroves dominated by L. racemosa and R. mangle. For tidal basins dominated by A. germinans, the maximum and minimum temperatures and monthly precipitation fit better seasonally with the vegetation indices (r ≥ 0.58, p < 0.0001). Significant mangrove canopy reductions were identified in all the analyzed tidal basins (z values for the Mann-Kendall test ≤ −1.96), but positive change trends were recorded in four of the basins, while most of the mangrove canopy (approximately 87%) displayed only seasonal canopy changes or canopy recovery (z > −1.96). The most resilient mangrove forests were distributed in tidal basins dominated by L. racemosa and R. mangle (Mann-Kendal Tau t ≥ 0.4, p ≤ 0.03), while basins dominated by A. germinans showed the most evidence of disturbance.

A partir de 18 variables características del hábitat actual de Quercus suber L. en el centro-oeste de España (Salamanca y Zamora), se ha cartografiado el área potencial climática para la especie así como los límites máximos de las áreas potenciales considerando no sólo los factores climáticos sino tres variables edafoclimáticas para dos hipótesis extremas de capacidad de retención de agua (CRA): CRA baja (50 mm) y CRA elevada (250 mm). Por último, se han tenido en cuenta las posibles limitaciones derivadas de la reacción del suelo. Los resultados obtenidos muestran la notable potencialidad climática de la zona para el alcornoque. Asimismo, se ha constatado que las áreas climática y edafoclimáticamente aptas para el alcornoque en el área española occidental de la cuenca del Duero presentan una notable dependencia de la CRA que condiciona no sólo su carácter central o marginal sino, en buena medida, su extensión. En la cuenca del Tajo, al sur de Salamanca, esta dependencia es notablemente menor.