Nutrition of cocoa rootstocks (Theobroma Cacao L.) using different doses of formula 15-15-15 and its influence on grafting of four types of graft

Abstract

With the aim of evaluating the influence of cocoa nutrition with different doses of formula 15-15-15, in the development of cocoa rootstocks and the success in graft grafting. An investigation was carried out in the nursery of the Faculty of Agronomic Sciences of the University of El Salvador. The research was carried out in two stages, in the first stage five doses of the formula 15-15-15 were defined: 5 g, 10 g, 15 g, 20 g, 30 g and a control to which no fertilizer was applied. Statistical analysis was performed using a completely randomized design with three replications and 40 plants as an experimental unit totaling 600 plants. In the second stage a factorial arrangement was made, where the doses of NPK and the type of graft (lateral plating, terminal wedge, yolk and patch) were combined, generating 20 treatments (four treatments per dose), in a completely randomized design with three repetitions and 10 plants per experimental unit, in addition to knowing the influence between the variables Pearson's correlation was used. The variables evaluated were: height, diameter, number of leaves, leaf area, specific leaf weight (PEH), chlorophyll content, fresh and dry leaf weight, stem and root of rootstocks in the first stage. In addition, the variables graft success were evaluated, days of development (GDD), height, diameter and number of graft sheets in the second stage. As a result, there were only significant statistical differences in plant diameter, leaf area and PEH, demonstrating that the different doses of the formula improved the development of the rootstocks with respect to the control. In the second global stage of the experiment, a 72% graft yield was obtained, the success being segregated by graft type: yolk 19.83%, terminal wedge 18.33%, patch 17.33 and lateral plating 16.51%. On the other hand, the finding of GDD requirements for lateral plating and terminal wedge grafts with an interval of 245-398 GDD (20-30 days) is reported, for sprouting and grafts where yolk is used, 403-522 is required. GDD (more than two months). It is concluded that the effect of the fertilizer was more categorical in the grafting phase, finding highly significant differences in the growth variables and a close association of these with the physiological variables of the rootstock stage demonstrated by the high positive correlation found between them and all influenced with the doses of the formula 15-15-15; considering that the assimilation and accumulation of reserves by the rootstocks and their translocation to the grafts and their growth variables was effective.