Phenological variations of avocado cv. Hass and their relationship with thermal time under tropical conditions.

In recent years, the avocado has been one of the most dynamic fruits in the world market. In particular, cv. Hass stands out due to its productivity, nutritional quality, and acceptance. Under tropical conditions, weather elements, especially air temperature, and precipitation, affect the productivity and quality of cv. Hass. However, in tropical environments, many relationships between weather and phenological aspects of this cultivar are still unknown. Given this situation, our aim was to identify the variation and degree of association between the phenology of avocado cv. Hass and thermal time (TT) under low-latitude conditions. Eight commercial fields planted with cv. Hass grafted onto Antillean genotypes, located in an altitudinal transect between 1,700 and 2,500 m, were evaluated. The evaluation was carried out for three years and was focused on determining the differences in avocado phenological patterns associated with different environmental variables monitored by weather stations at each location. Air temperature data were used to calculate the base temperature (BT) using different methods for all phenological stages. Later the TT was determined for each stage and all locations. The results show that the duration of each phenological stage varies as a function of elevation (air temperature) and that the phenological stages overlap at the regional, crop field, and plant levels at different periods of the year, generating a high phenological variability but with specific patterns associated with temperature and precipitation. The BT for each phenological stage varied between 0.3 and 7.5 °C, and TT was found to vary depending on the method of calculation. Our work suggests that the generalization of a BT of 10 °C is not applicable for avocado cv. Hass crops under tropical conditions, specifically in the case of Colombia. Detailed studies of phenological relationships with respect to climatic variables will allow a better approximation of the productive behavior of avocado cv. Hass.

Comparison of air temperature measured in a vineyard canopy and at a standard weather station.

The complex environment within a crop canopy leads to a high variability of the air temperature within the canopy, and, therefore, air temperature measured at a weather station (WS) does not represent the internal energy within a crop. The objectives of this study were to quantify the difference between the air temperature measured at a standard WS and the air temperature within a six-year-old vineyard (cv. Chardonnay) and to determine the degree of uncertainty associated with the assumption that there is no difference between the two temperatures when air temperature is used as input in grapevine models. Thermistors and thermocouples were installed within the vine canopy at heights of 0.5 m and 1.2 m above the soil surface and immediately adjacent to the berry clusters. In the middle of the clusters sensors were installed to determine the temperature of the air surrounding the clusters facing east and west. The data were recorded within the canopy from December 2015 to June 2017 as well as at the standard WS that was installed close to the vineyard (410 m). Significant differences were found between the air temperatures measured at the WS and those within the vineyard during the summer when the average daily minimum air temperature within the canopy was 1.2°C less than at the WS and the average daily maximum air temperature in the canopy was 2.0°C higher than at the WS. The mean maximum air temperature measured in the clusters facing east was 1.5°C higher and west 4.0°C higher than the temperature measured at the WS. Therefore, models that assume that air temperature measured at a weather station is similar to air temperature measured in the vineyard canopy could have greater uncertainty than models that consider the temperature within the canopy.

Caracterización del efecto de "el niño" y "la niña" sobre la lluvia de la zona cafetera Colombiana / Characterizaton of "el niño" and "la niña" effect on rainfal on the Colombiian coffee growing regoon

El clima es y seguirá siendo la principal variable que domina el crecimiento y desarrollo de las plantas. La lluvia, especialmente el acumulado de esta en un periodo de tiempo dado, tiene efecto directo sobre la fisiología y el desarrollo de los cultivos, mientras que la forma en que se distribuye la precipitación a través del año tiene un efecto significativo sobre la producción. A diferencia de otros estudios que se enfocan en evaluar el efecto de generadores de variabilidad climática sobre el acumulado de lluvias, este estudio tuvo como objetivo determinar el efecto de "El Niño" y "La Niña" sobre el comportamiento medio intraanual de la precipitación de la zona cafetera colombiana. Se utilizaron datos diarios de lluvia provenientes de 80 estaciones meteorológicas, que tienen registros continuos superiores a 25 años y que hacen parte de la red climática de la Federación Nacional de Cafeteros de Colombia, y conglomeración estadística para agrupar zonas en las que el efecto de "El Niño" y "La Niña" es similar. Se encontraron cuatro grupos que sintetizan los cuatro tipos de efectos de estos moduladores sobre la lluvia de la zona cafetera. Los resultados obtenidos evidencian que los departamentos que tienen una mayor amenaza causada por estos fenómenos son Caldas, Quindío, Risaralda, Tolima y la zona Norte del país.

The climate is and will continue to be the principal variable that dominates the growth and development of plants. Rain, specially its accumulation in a given period of time, has direct effect on the physiology and the development of crops, while the way in which precipitation is distributed throughout the year has a significant effect on production. Unlike other studies that focus in evaluating the effect of climatic variability generators on the accumulation of rain, this study aimed to determine the effect of "El Niño" and "La Niña" on the average behavior of intra-annual precipitation in the Colombian coffee region. Daily rainfall data from 80 weather stations with 25 years of continuous records that are part of National Federation of Colombian Coffee Growers were used as well as statistical conglomeration in order to to group zones in which the effect of "El Niño" and "La Niña" is similar. Four groups that synthesize four types of effects of these modulators on the rain of the coffee region were found. The results show that the departments that have a major threat caused by these phenomena are Caldas, Quindío, Risaralda, Tolima and the northern area of the country.