Abstract Tabebuia rosea is a native tropical tree species with high potential of implementation in commercial reforestation and ecological restoration. We studied the effect of the suppression of essential nutrients on the growth of T. rosea in the nursery. The design was completely randomized with ten treatments: one that included full fertilization, another without fertilization, and the others with the suppression of N, P, K, Ca, Mg, S, B, and cationic microelements. Biometric variables (height, stem diameter, shoot dry weight, root dry weight) and functional traits (leaf area and relative growth rate) were evaluated. Phosphorus was the most limiting element. On the contrary, the suppression of Ca generated plants with growth and development similar to those of the FF treatment. Our results confirmed the importance of knowing the particular nutritional needs of individual species, which is to support nursery fertilization practices that produce highly vigorous and quality plants.

RESUMEN Los suelos tropicales son característicamente ácidos y pobres en nutrientes, lo cual limita su productividad agrícola. Estos suelos usualmente son tratados con cal, pero su baja solubilidad limita su efectividad para mejorar la fertilidad. El uso de yeso agrícola ha ganado mucha atención debido a su mayor solubilidad y movilidad en el suelo, disponibilidad local y bajo precio. Por tanto, se realizó un estudio para determinar tales efectos en diez suelos acidos Colombianos con baja fertilidad y diferentes características físicas y químicas. Muestras de estos suelos (0-20 cm) se secaron al aire, tamizaron (<2 mm) y transfirieron a vasos plásticos. Dosis crecientes de yeso se aplicaron por cuadruplicado: 0,0; 0,25; 0,5; 1,0; 2,0; 4,0; 8,0 y 16,0 g kg-1. Los suelos se humedecieron para mantenerlos a 50% de su máxima capacidad de retención de agua durante dos semanas. Se midió pH, Al+3, Ca+2, Mg+2, K+, S-SO4 -2 y P-H2PO4 -2 usando métodos estandarizados. Los resultados muestran que al adicionar yeso agrícola se incrementó significativamente (P<0,05) los niveles de Ca+2-K+ intercambiable, saturación de Ca+2 , S-SO4 -2 y Al+3 intercambiable, particularmente con dosis mayores de 4,0 g kg-1. En contraste, con el incremento de la dosis de yeso agrícola disminuyeron significativamente la saturación de Al+3 , y el pH; los niveles de Mg+2 no fueron significativamente afectados. El uso de las pruebas de incubación de yeso agrícola es promisorio para detectar mejoras en el suelo a través del incremento en los niveles de Ca2+ y S-SO4 2- y la disminución de la saturación de Al3+.

ABSTRACT Tropical soils are characterized by acidity and poor plant nutrient availability, limiting their agricultural productivity. These soils are commonly amended with lime, but its low solubility impairs its effectiveness to enhance soil fertility. The use of gypsum has gained attention among farmers due to its higher solubility and mobility in the soil, local accessibility, and low price. Therefore, this study was conducted to determine the effects of Agricultural Gypsum (AG) addition on ten Colombian acid soils that had poor fertility and contrasting their physical and chemical characteristics. Surface (0-20 cm) soil samples were air-dried, sieved (<2 mm), and transferred into plastic vases, 40 g (dry base) per vase. Increasing rates of gypsum were added by duplicate: 0.0, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0, and 16.0 g kg-1. Then, the soils were incubated for two weeks and watered to maintain 50% of their maximum water holding capacity. Soil pH, Al+3, Ca+2, Mg+2, K+, S-SO4 -2, and P-H2PO4 -2 were measured using standard methods. The results showed that AG addition significantly (P<0.05) increased soil exchangeable Ca+2-K+, Ca+2 saturation, S-SO4 -2 concentration, and exchangeable Al+3, particularly with doses above 4.0 g kg-1. In contrast, soil Al+3 saturation, P-H2PO4 -2 and pH significantly decreased as the AG doses increased, while soil exchangeable Mg+2 levels were not significantly affected. The use of gypsum incubation tests could be promissory for its effects on soil amelioration associated mainly to increase soil exchangeable Ca2+ and S-SO4 2- and to decrease Al3+ saturation.

ABSTRACT Avocado is currently an important crop in Colombia, given its growth in planted area and the increase in exports. The destination market of Colombian avocado is mainly international, and its quality is outstanding. However, the physical and chemical characteristics associated with the quality of the avocados produced are not currently well known in Colombia. The aim of this study was to evaluate the physical, chemical and nutritional parameters associated with the quality of Hass avocado in eight localities of the department of Antioquia based on descriptive statistics. Additionally, the quality was related to the localities through a multivariate analysis. As a result, quality at preharvest parameters of Hass avocados cultivated in Antioquia is similar or superior to that reported internationally based on physical and chemical variables. In addition, a relationship was established between the quality of fruits and the plots where these were cultivated, which allowed discriminating fruits by their region of origin. This work shows an approach to the determination of quality parameters in Hass avocado in Colombia and how they can be related to the characteristics of its productive system, which can lead to defining a product with added value.

RESUMEN El cultivo del caucho es un rubro agrícola de importancia ambiental y socioeconómica para Colombia, por ser una alternativa diferente de las actividades mineras y agropecuarias tradicionales; incluso, representa una opción beneficiosa para la sustitución de cultivos de uso ilícito. Lo anterior muestra la necesidad de determinar los factores que restringen su producción y la productividad de la especie, con énfasis en lo relacionado al recurso edáfico. En ese sentido, se hizo la descripción y la identificación de las propiedades físicas y químicas del suelo de tres predios ubicados en el Bajo Cauca Antioqueño dedicados a la explotación de la euforbiácea. Los resultados indicaron que los suelos son del orden Ultisol, profundos, de reacción ácida y con contenido bajo de materia orgánica; los elementos esenciales están en niveles bajos, excepto el Cu. El Fe y el Al se encuentran en cantidades muy altas, mientras que la capacidad de intercambio catiónico es limitada. Lo observado alerta sobre la necesidad de aplicar técnicas de manejo agronómico que permitan que esta especie exprese todo su potencial en condiciones que son poco aptas para su crecimiento y desarrollo.

ABSTRACT From a socioeconomic and environmental standpoint, rubber cultivation is potentially important for Colombia, because it not only constitutes an alternative to the traditional mining, agricultural, and livestock activities, but also a beneficial option in the substitution of illegal crops. Thus, there is need to determine the factors restricting the productivity of the species, particularly soil-related aspects. In this context, the current research undertook the description and identification of soil physical and chemical properties in three rubber plantations located in a region known as Bajo Cauca Antioqueño, at the lower course of the Cauca river. The results indicate that these soils are classified as Ultisols, they are deep, with acid reaction and low levels of soil organic matter. Essential elements also exhibited low levels, except Cu. Fe and Al are also present in very high concentrations, while the cation exchange capacity is limited. These observations alert on the need for agronomic management techniques that allow the crop to express its full potential under conditions that are not very adequate for its growth and development.

RESUMEN En los últimos años, el cultivo de cacao (Theobroma cacao L.) en Colombia viene creciendo, esto hace necesario desarrollar un sistema de producción sostenible. Es así, como los micro organismos benéficos del suelo son una excelente alternativa para mejorar la productividad de la planta, pero es importante conocer su funcionamiento y ecología. Este trabajo tuvo como objetivo identificar y cuantificar hongos micorrízicos arbus culares (HMA) y Pseudomonas sp. fluorescente associados al suelo y la rizosfera de plantas de cacao en dos agroecosistemas, bosque seco tropical (BST) y bosque húmedo tropical (BHT). En una segunda etapa del trabajo se seleccionaron y multiplicaron cepas nativas de Glomus sp., Acaulospora sp., y Pseudomonas sp. fluorescente en el laboratorio. Asi la efectividad de estas cepas para promover el crecimiento de plántulas de cacao bajo condiciones de invernadero fue evaluada. Los resultados indican que hubo una diferencia significativamente (P<0.5) mayor en la colonización micorrizal y diversidad asociada a raíces de cacao creciendo en el agroeosistema asociado al bosque húmedo tropical. Sin embargo, no se encontraron dife rencias significativas asociados a la presencia a Pseudomonas sp. fluorescente asociados a los dos agroecosistemas. Por otro parte en los experimentos en invernadero, la inoculación con el hongo micorrízico Glomus sp. fue el único tratamiento que promovió el crecimiento de plántulas de cacao.

ABSTRACT In recent years the cultivation of cacao (Theobroma cacao L.) in Colombia has been growing up, resulting in the need to develop a sustainable production system. In this regard, ben eficial soil microorganisms are an alternative for improving plant productivity, but this requires knowledge of their ecology and functioning. This study had the objective of identify and quantify arbuscular mycorrhizal fungi (AMF) and fluorescent Pseudomonas sp. associated with the soil and rhizosphere of cacao plants in two agroecosystems, one of them was in a tropi cal dry forest (TDF) and the other in a tropical moist forest (TMF). In a second stage of the study, native strains of Glomus sp., Acaulospora sp., and fluorescent Pseudomonas sp. were se lected and multiplied in the lab. Subsequently, the effectiveness of these strains to promote cacao seedling growth was tested in a greenhouse experiment. The results indicate that there was a significant (P<0.05) greater mycorrhizal colonization and diversity associated to the roots of cacao growing in agroeco systems of the tropical moist forest. However, not significant differences were detected regarding the presence of fluorescent Pseudomonas sp. in the two agroecosystems. Otherwise, in the greenhouse experiments, the inoculation with the mycorrhizal fungus Glomus sp. was the only treatment that promoted the cacao seedling growth.

Una de las técnicas más importantes para promover el crecimiento vegetal en el invernadero de especies forestales es el uso de microorganismos rizosféricos. Esto es particularmente relevante para mejorar el desarrollo vegetal en programas de reforestación de tierras degradadas. Una serie de experimentos se realizaron para evaluar la efectividad de inoculaciones individuales y combinadas con el hongo micorrícico arbuscular Rhizoglomus fasciculatum (Thaxt.) Sieverding, G.A. Silva & Oehl y el hongo solubilizador de fosforo (P) Mortierella sp., a dos dosis (50 y 100 kg de inóculo por m³ de sustrato) sobre el crecimiento y absorción de P de Tecoma stans, Dodonaea viscosa, Fraxinus chinensis y Lafoensia speciosa. Estas especies vegetales son comúnmente usadas en Colombia en programas de reforestación. Los resultados indican que los tratamientos fueron efectivos para incrementar el crecimiento y la absorción de P de las cuatro especies; sin embargo, el efecto fue significativamente mayor cuando ambos hongos R. fasciculatum y Mortierella sp., fueron conjuntamente inoculados que cuando se usó sólo R. fasciculatum. En general, la inoculación dual en una dosis de 50 kg m-3 tuvo efectos significativamente mayores o similares que la dosis de 100 kg m-3. Estos resultados sugieren que la doble inoculación fue más efectiva para prevenir la deficiencia de P y estimular el crecimiento vegetal.

One of the most promising techniques to promote seedling growth of tree species at nursery is the use of rhizosphere microorganisms. This is particularly relevant in enhancing plant performance in reforestation of degraded lands. A series of experiments were conducted to evaluate the effectiveness of either individual inoculation with the arbuscular mycorrhizal fungus Rhizoglomus fasciculatum (Thaxt.) Sieverding, Silva & Oehl or dual inoculation with R. fasciculatum and the phosphate solubilizing fungus Mortierella sp., at two doses (50 and 100 kg of inoculum per m³ of substrate), on plant growth and phosphorus (P) uptake of Tecoma stans, Dodonaea viscosa, Fraxinus chinensis, and Lafoensia speciosa. These plant species are commonly used in Colombia in reforestation programs. The results indicated that treatments were effective to increase plant performance of the four plant species; however, the effect was significantly higher when both fungi R. fasciculatum and Mortierella sp. were concomitantly inoculated than when only the mycorrhizal fungus was applied. Overall, the dual inoculation at the dose of 50 kg m-3 had higher or similar effects than at 100 kg m-3. The results suggest that the dual inoculation was more effective in order to prevent plant P deficiency and stimulate plant growth.

RESUMOO cultivo de maracujazeiro roxo tem aumentado na Colômbia, como resultado direto do seu consumo bem aceito. Diante disso, há necessidade de soluções tecnológicas voltadas para o crescimento sustentável do seu fruto, como a melhoria da germinação de sementes e diminuição das deficiências de fósforo (P), dada a sua baixa disponibilidade em solos tropicais. Assim, este estudo objetivou avaliar tratamentos pré-germinativos (controle, cortes da porção apical e basal das sementes, alternância de temperatura, fotoperíodo, aplicação de ácido giberélico e imersão em 96 % de H2SO4) e a dependência micorrízica de plantas de maracujá roxo, utilizando-se três níveis de P na solução do solo (0,002 mg L-1, 0,02 mg L-1 e 0,2 mg L-1), em 35 combinações com inoculação ou não do fungo micorrízico Glomus fasciculatum. Utilizou-se delineamento inteiramente casualizado, com cinco repetições por tratamento. O tratamento com efeito mais significativo sobre a redução da dormência das sementes de maracujá roxo é a imersão em 96 % de H2SO4, durante 20 minutos. Esta espécie apresenta alta dependência micorrízica, quando conjugada com 0,02 mg L-1 de P na solução do solo.

ABSTRACTThe cultivation of purple passion fruit plants has increased in Colombia, as a direct result of its well-accepted consumption. Therefore, there is a need for technological solutions aimed at the sustainable growth of its fruit, such as improving seed germination and decreasing phosphorus (P) deficiencies, given its low availability in tropical soils. This study aimed to evaluate pre-germination treatments (control, apical and basal seed cuts, alternation of temperature, photoperiod, application of gibberellic acid and immersion in 96 % of H2SO4) and mycorrhizal dependency of purple passion fruit plants, using three levels of P in the soil solution (0.002 mg L-1, 0.02 mg L-1 and 0.2 mg L-1), in 35 combinations with or without the inoculation of the Glomus fasciculatum mycorrhizal fungus. A completely randomized design with five replications per treatment was used. The treatment with the most significant effect for reducing the dormancy of the purple passion fruit seeds is the immersion in 96 % of H2SO4 for 20 minutes. This species shows a high mycorrhizal dependency, when coupled with 0.02 mg L-1 of P in the soil solution.

La identificación de síntomas visuales de deficiencias es un método muy utilizado en el diagnóstico de problemas nutricionales en la producción agrícola y forestal. El objetivo de este trabajo fue caracterizar los síntomas visuales de deficiencias de N, P, K, Ca, Mg, S, y B, en plántulas de roble andino Quercus humboldtii Bonpl., en condición de vivero. Las plántulas se sembraron en bolsas de polietileno, en cuyos sustratos se aplicaron los tratamientos de fertilización de acuerdo con el método de Jenny. Luego de 4 meses de desarrollo se fotografiaron las plántulas y hojas en las que se observaron los síntomas de deficiencias nutricionales y se determinó el contenido de nutrientes foliares. Se detectaron síntomas de deficiencia de todos los nutrientes estudiados, excepto de B. Las plántulas deficientes en cada nutriente presentaron menor concentración de éste elemento en los tejidos foliares. La dosis aplicada de P al parecer no fue suficiente para tener una disponibilidad adecuada del elemento y generar un óptimo desarrollo de las plántulas de Q. humboldtii con tratamiento completo de fertilización.

The identification of visual symptoms of deficiencies is a widely used method in the diagnosis of nutritional problems in agricultural and forestry production. The aim of this study was to characterize visual symptoms of deficiencies of N, P, K, Ca, Mg, S and B, in seedlings of the andean oak, Quercus humboldtii Bonpl., under nursery conditions. Seedlings were planted in polythene bags, where fertility treatments were applied according to the method of Jenny. After 4 months of development, we photographed seedlings and leaves with symptoms of nutritional deficiencies and determined leaf nutrient content. Deficiency symptoms were detected for all nutrients studied, except B. Seedlings deficient in each nutrient had lower concentration of this element in leaf tissues. The applied dose of P was apparently not enough to have an adequate availability of this nutrient and to generate an optimal development of seed- lings of Q. humboldtii under full fertilization.

Quercus humboldtii es una especie vegetal nativa de mucha importancia en Colombia por su uso en repoblamiento forestal y restauración de tierras altoandinas degradadas. La especie se encuentra fuertemente amenazada y es necesario establecer programas de propagación de la misma. Sin embargo, poco se conoce sobre sus exigencias nutricionales y lumínicas. El objetivo de este estudio fue determinar los efectos simples y combinados de la iluminación relativa (IR) y la fertilización sobre el crecimiento de plántulas de Q. humboldtii en vivero. Para esto se establecieron en combinación tres condiciones contrastantes de iluminación relativa (alta, media y baja IR) y nueve tratamientos de fertilización: completa (TC), con un elemento faltante (-N, -P, -K, -Ca, -Mg, -S, -B) y un testigo sin fertilización (T0). La condición de IR media presentó el mejor desarrollo de las plántulas. Todos los tratamientos con deficiencias nutricionales produjeron disminuciones en el desarrollo de las plántulas con respecto a TC, excepto en el tratamiento -B. El N fue el elemento más limitante, con rendimientos similares a los del tratamiento testigo. El orden de limitación que produjeron los tratamientos aplicados siguió la secuencia: T0,-N > -Ca, -K, - P > -Mg, -S > TC,-B. No se detectó interacción significativa IR x Fertilización sobre el desarrollo de las plántulas.

Quercus humboldtii is a native plant species of great importance in Colombia for use in reforestation and restoration of degraded Andean highlands. The species is highly threatened and it is necessary to establish programs of propagation and planting. However, little is known about their nutritional and light requirements. The aim of this study was to determine the effects of single and combined relative illumination (IR) and fertilization on the growth of seedlings of Q. humboldtii at nursery. For this purpose three contrasting IR regimes (high, medium, and low IR) and nine fertilization treatments were established: complete (TC), a missing nutrient (-N,-P,-K,-Ca,-Mg, -S,-B) and a control without fertilization (T0). The best development of seedlings was showed in the medium IR condition. All treatments with a lacking nutrient showed decreases in seedling development regarding TC, except in the -B treatment. Nitrogen was the most limiting nutrient yielding biomass similar to that of T0. The impact of nutrient limitation on seedling performance was in the following order:-N>-Ca,-K,-P>-Mg,-S>-B. No significant interaction IR x Fertilization was detected on seedling development.