Incidence of Substrate Type and Hormone Application on Oil Carob (Pongamia pinnata L. Pierre) Multiplication by Root Cuttings in Different Seasons

Pongamia pinnata L. Pierre is a multipurpose oil tree species, a source of renewable biofuel, in addition to being a recuperator of degraded soils due to its capacity to fix nitrogen. The most common form of propagation is through seeds, but there is little information available on its vegetative propagation, with asexual propagation being essential to maintain the characteristics of the mother plant and avoid variability. The objective of this work was to evaluate the incidence of substrate type, rooting hormone application and time of year on the vegetative propagation capacity of P. pinnata by means of root cuttings. The experiment was carried out in the Forest Nursery of the Faculty of Agricultural Sciences, National University of Asunción. A completely randomized design with factorial arrangement (3×2×2) was used, composed of 3 types of substrates, 2 times of the year, with and without application of IBA hormone. The variables evaluated were: percentage of survival and rooting, number of rootlets, rootlet length and rooting index. The data were subjected to analysis of variance (ANOVA) and in cases where significant differences were found, means were compared using Tukey's test at 5% probability. The results indicate that Pongamia cuttings are not significantly influenced by the application of the IBA hormone and the type of substrate. However, they are significantly influenced by the time of year, with spring-summer being the best time for propagation by root cuttings, as demonstrated in this study.