Is guamo (Inga densiflora Benth.) a beneficial tree as a companion of coffee seedlings under differential fertilization?

Abstract

The use of leguminous trees as shade for coffee plantations could be part of future agricultural strategies in the tropics to face climate change. The so-called “guamo” (Inga spp., Fabaceae) is a beneficial leguminous tree traditionally used for buffering microclimate and improving soil properties. However, it is not yet known whether the closeness of planted guamo seedlings brings benefits to coffee crops when they are established or whether this benefit comes with time. To examine whether the proximity of guamo affected the growth of coffee seedlings under different fertilization conditions, we planted 360 three-month-old guamo seedlings and 90 coffee seedlings of the same age in an 1800 m2 plot using a stratified randomized design consisting of 90 plots and 270 subplots. We randomly assigned three treatments (guamo, coffee, and control without fertilizer), two fertilizers (commercial chicken manure and organic copolymer), and the control. Monthly growth measures were taken for a year. Seedlings grew the most with chicken manure (23.4% and 27.8% greater diameter than that obtained with the copolymer and the control, respectively) while the height was 19.9% greater than that obtained with the copolymer and 22.6% greater than the control. The evidence supports that chicken manure was an effective organic fertilizer and the presence of guamo neither benefitted (via facilitation) nor damaged (via interspecific competition) the coffee saplings during the establishment of the plantation.