Cadmium is a toxic non-essential metal for almost all living systems. It is one of the biggest challenges for farmlands and the food chain because of its toxic effect on human health. This research aims to determine the Cd content in soils, litter and cacao beans, following the Cd fluxes within each cacao system using the two-dimensional electrical resistivity tomography technique. The study was carried out in four farms located in the Magdalena basin in Antioquia, Colombia. The farms showed a heterogeneity in relation to cacao cultivars, altitude, topography and geology. The soil cation electrical capacity, pH and soil organic matter levels, as well as the Al, Al 3+ H + , Ca, K, Mg and P contents were measured at different depths. Moreover, the Cd content was correlated to the resistivity values of samples taken in situ using ERT. Soil Al 3+ H + and the altitude of the farms fitted as the best predictors of the beans' Cd content. Furthermore, the Cd content in soils from the assessed farms ranged between 1.22 and 2.03 mg kg −1 . The Cd content in cocoa beans ranged from 0.07 to 1.44 mg kg −1 , with a value of 0.40 mg kg −1 on average. The resistivity values obtained in field showed a high correlation with the soil Cd content determined (R 2 = 0.82). The predictive tomography plots highlighted topsoil Cd dynamics between litter, amendments and fertilizers. Therefore, these results underlie the utility of the combined geophysical techniques and soil chemical properties including the analysis of fertilizer amendments to improve the understanding of Cd dynamic.

Cocoa crop in Colombia is characterized by low technified systems, with yields below 500 kg ha-1 year-1. Inappropriate application of cultural practices related to the lack of knowledge about cocoa phenology, as to the times and factors that induce flowering, shoot growth and fruit filling, is one of the principal causes. Phenology of cocoa clones CCN-51, ICS-95, FCH-25 y LK-40 was characterized in 4 years old trees, data were taken monthly for one year in a Tropical moist forest (T-mf), with unimodal rainfall regime, in the municipality of Chigorodó (Antioquia), coordinates 7° 36´ 52.5473´´ N, 76° 39´ 32.8495´´ W and 30 m above sea level, Mi Fortuna farm. The correlation (Spearman) between precipitation, water balance, number of hours with photosynthetically active radiation between 750 and 2200 µmol m-2 s-1 (PAR hours) and the maximum and minimum temperature with vegetative and reproductive variables was calculated. A significant correlation (p<0.001) between flowering and precipitation, water balance and PAR hours was found. Vegetative growth rate was controlled by fruit filling and harvest (source-sink ratio). The reproductive performance of LK-40 was superior to that of CCN-51 and similar to that of ICS-95 and FCH-25; clon CCN-51 showed the highest vegetative growth, but its reproductive performance was less than ICS-95 and LK-40.

El objetivo fue conocer el comportamiento de Hevea brasiliensis a partir del desempeño fotosintético en las regiones caucheras de Nordeste y Bajo Cauca de Antioquia (Colombia) como base para futuros estudios de desempeño clonal entre ambientes. Se cuantificó el intercambio de gases mediante un analizador infrarrojo de gases portátil; para las variables fotosintéticas se calculó un valor medio para los siete clones, a partir del cual se estimó el área bajo la curva. El máximo valor de fotosíntesis se alcanzó a las 8 horas en San Roque (10,97 µmol [CO2] m-2s-1) y 9 horas en Caucasia (7,84 µmol [CO2] m-2s-1). La transpiración máxima fue 3,55 mmol [H2O] m-2s-1 en el municipio de San Roque y 5,16 mmol [H2O] m-2s-1 en Caucasia, mientras que la conductancia estomática máxima fue 0,18 mol [CO2] m-2s-1 y 0,16 mol [CO2] m-2s-1 respectivamente para cada localidad. Las plantas de caucho en Caucasia presentaron mayor tasa de asimilación neta acumulada 271.934 µmol [CO2] m-2día-1, superando los 226.287 µmol [CO2] m-2día-1 en San Roque y, representado en una diferencia de 45.647,52 [CO2] µmol m-2día-1. La mayor acumulación de carbono con menor inversión de energía lumínica (697.638 µmol [CO2] µmol fotón-1día-1) se obtuvo en San Roque. Hevea brasiliensis presentó una mayor adaptación ambiental con respecto al intercambio gaseoso y el uso de la energía lumínica en San Roque.

Annual defoliation and refoliation cycles that occur in rubber trees after 5 years of age have a strong interaction with foliar diseases attacks. The rubber phenology was studied in the eastern plains of Colombia, in the municipality of Puerto López, department of Meta, where variables such as foliar density, percentage of leaves in stages A, B, C and D and flowering density were evaluated in clones IAN 873, FX 3864 and RRIM 600, between August 2016 and September 2018. All three clones showed a foliar density higher than 80% with leaves in stage D, between March and December (weeks 12–50 of the year). The defoliation started in the last weeks of the year, with the beginning of the dry season. The refoliation extended until mid-March (week 11) in 2017, and until February (week 6) in 2018. The presence of leaves in stages A, B and C during 8–13 weeks was observed at the plantation level, according to the clone and the evaluation year. The duration of the refoliation per tree was on average 6.73 ± 0.22 weeks in 2017 and 4.42 ± 0.39 weeks in 2018. Flowering coincided with refoliation, during a period of negative water balance and high solar radiation. Expansion of inflorescences was observed in the first weeks of the year between January and March, with the absence of reproductive development when the crop was dominated by leaves in stage D.

In agriculture, agroclimatic zoning procedures through geographic information systems provide producers, technical assistants, decision-makers, and investors with land-use planning and decision-making tools. This study aims at identifying and delimiting areas suitable for the cultivation of rubber [Hevea brasiliensis Willd. ex A. Juss.) Müll. Arg.] in Colombia, using the species requirements at a scale of 1:100,000, as well as identifying escape zones for the South American leaf blight (SALB) disease (caused by the fungus Pseudocercospora ulei). The study was carried out following the agroecological zoning methodology for the definition of land use proposed by the Food and Agriculture Organization of the United Nations. Spatial analysis tools were used to raster data with ArcGIS Desktop 10.7, incorporating and evaluating climatic and soil variables. The obtained results showed that there are 5,480,543 ha suitable for cultivating natural rubber in Colombia. However, these areas present favorable climatic conditions for the development of the SALB. INTRODUCTIONNatural rubber [Hevea brasiliensis (Will. Ex A. Juss.) Müll.Arg.] is a fast-growing plant of tropical origin adapted to various environmental conditions. It is cultivated in the tropicequatorial region between 10˚N and S latitude, with higher productivity from 6˚N and S latitude (Escobar-Acevedo et al.,Abbreviations: EZ, Escape zones; SALB, South American leaf blight.