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.

ABSTRACT Damping-off is considered one of the most serious risks for production of Pinus seedlings due to the significant losses it can cause in forest nurseries. In Colombia there is little information about the etiology of this limiting disease. Different species of the genus Fusarium have been reported as causal agents, which makes the study of the pathogenicity of this genus relevant. In this study, strain 001F of Fusarium oxysporum was obtained from the diseased tissues of P. patula seedlings. The identity of the species was determined by sequencing the internal transcribed spacer (ITS) regions. Pathogenicity tests confirmed the ability of strain 001F to cause damping-off symptoms in P. patula and P. tecunumanii. Thus, F. oxysporum strain 001F represents a significant risk to produce tree species in Colombia and in other parts of the world.

Se estudió la dinámica fermentativa in vitro de los forrajes pasto estrella (Cynodon plectostachyus; E), pasto guinea (Megathyrsus maximus; G) y leucaena (Leucaena leucocephala; L), disponibles en sistemas silvopastoriles intensivos (SSPi). Se recolectaron muestras en SSPi establecidos en bosque seco tropical en el Valle del Cauca, Colombia. Se realizaron 10 mezclas o tratamientos con diferentes porcentajes de inclusión: E100, G100, L100, E33G66, E66G33, L33E66, L66E33, L33G66, L66G33 y L33E33G33. El menor tiempo de fase Lag se observó con L100 (7,02 h) y E33G66 (7,11 h), menores (a = 0,05) a L33E66 (10,22 h) y G100 (9,85 h). Las producciones máximas de gas (a) variaron entre 97,34 y 253 ml/g sustrato para L100 y G100, respectivamente. El menor valor de HPI se obtuvo con L100 (23,3 horas) y el gas acumulado a ese punto fue 35,08 ml, que coincide con el valor más bajo. Los tratamientos de mayor acumulación de gas fueron los que incluyeron gramíneas solas o sus mezclas y los de menor acumulación de gas fueron los que incluyeron leucaena. En cuanto al FP, a las 24 horas de incubación los valores más altos se presentaron con L100 y en las mezclas que incluyeron leucaena. Se concluye que la inclusión de leucaena estuvo asociada a disminuciones en el tiempo de fase lag y tasas máximas de producción de gas, así como con altos valores de FP, características que pueden asociarse a mayor eficiencia en los procesos de fermentación.

Abstract A study of the in vitro fermentation dynamics of the forages star grass (Cynodon plectostachyus; E), Guinea grass (Megathyrsus maximus; G) and Leucaena leucocephala (L), available in intensive silvopastoral systems (ISS) was carried out. Samples of these forages were harvested in ISS set in tropical dry forest in the Valle del Cauca, Colombia. With these forages, ten mixes or different treatments were generated: E100, G100, L100, E33G66, E66G33, L33E66, L66E33, L33G66, L66G33 and L33E33G33. The shorter lag phase was observed with L100 (7.02 h) and E33G66 (7.11 h), lower (a= 0.05) than that of L33E66 (10.22 h) and G100 (9.85 h). The maximum production of gas (a) ranged between 97.34 and 253 ml/ g substrate for L100 and G100, respectively. The lowest HIP value was obtained with L100 (23.3 hours) and the gas accumulated to that point was 35.08 ml, which coincides with the lower value. The treatments that most accumulated gas were the grasses alone or their mixtures and those with the least accumulated gas included leucaena. Regarding FP, after 24 hours of incubation, the greater values occurred with L100 and mixtures that included leucaena. It is concluded that the inclusion of Leucaena was associated with decreases in the lag phase time and maximum gas production rates and with high values of FP, characteristics that may be associated with more efficient fermentation processes.

Resumo Estudou-se a dinâmica fermentativa in vitro das forrageiras do capim estrela (Cynodon plectostachyus; E), capim coloni ão (Megathyrsus maximus; G) e leucaena (Leucaena leucocephala; L), disponíveis em sistemas silvopastoris intensivos (SSPi). Tomaram-se amostras em SSPi estabelecidos em bosque seco tropical no Vale do Cauca, Colômbia. Realizaram-se 10 misturas ou tratamentos com diferentes porcentagens de inclus ão: E100, G100, L100, E33G66, E66G33, L33E66, L66E33, L33G66, L66G33 e L33E33G33. O menor tempo da fase Lag se observou com L100 (7,02 h) e E33G66 (7,11 h), menores (a = 0,05) a L33E66 (10,22 h) e G100 (9,85 h). As produções máximas de gás (a) variaram entre 97,34 e 253 ml/g substrato para L100 e G100, respectivamente. O menor valor de HPI obteve-se com L100 (23,3 horas) e o gás acumulado nesse ponto foi 35,08 ml, que coincide com o menor valor. Os tratamentos de maior acumulação de gás foram os que incluíram gramíneas solas ou suas misturas e os de menor acumulação de gás foram os que incluíram leucaena. Em quanto ao FP, as 24 horas de incubação os valores maiores apresentaram-se com L100 e em misturas que incluíram leucaena. Pode se concluir que a inclus ão de leucaena esteve associada a diminuições no tempo de fase lag e taxas máximas de produção de gás, assim como com altos valores de FP, características que podem-se associar com a maior eficiência nos processos de fermentação.