Developing legume shade trees for Sustainable coffee production in Puerto Rico

Project Overview

Project Type: Research and Education
Funds awarded in 2004: $195,298.00
Projected End Date: 12/31/2008
Region: Southern
State: Puerto Rico
Principal Investigator:
Eduardo Schröder
University of Puerto Rico

Annual Reports


  • Additional Plants: native plants


  • Crop Production: agroforestry, biological inoculants
  • Education and Training: demonstration, workshop, technical assistance
  • Natural Resources/Environment: biodiversity, habitat enhancement


    Coffee production in Puerto Rico is located in the central mountain region, mostly on acid, highly erodible soils. To improve sustainable production of high quality coffee, we collected soil, weather, and biomass production potential for the whole island and generated the first coffee agro ecological map. Traditional farms producing shaded coffee in 20 municipalities were surveyed. In each farm, tree species were identified and data georeferenciated with GPS and GIS. Soils of the coffee region were characterized. Nitrogen mineralization potential was measured, and with litter fall data, balance of N supplied for coffee estimated. Field sampling was performed to evaluate different sources of N fixation and the microbial soil population structure. Finally, the potential of more than 28 species of fast-growing nitrogen fixing trees was evaluated in two representative soils, with and without pH and nutrient supplements.

    Tables, figures or graphs mentioned in this report
    are on file in the Southern SARE office.
    Contact Sue Blum at 770-229-3350 or for a hard copy.

    Project objectives:

    Objective 1. Survey present coffee production systems used by farmers in Puerto Rico

    Objective 2. Evaluate the potential value of fast-growing nitrogen-fixing trees for the production of shade coffee.

    Objective 1. During the project, the fieldwork data analysis and final writing for this objective has been completed by Mr. Miguel Arango (MS student). Using the amount of coffee produced by municipality, the 20 highest coffee producing municipalities were selected for field sampling. Combing the number of farms with shaded coffee with the map of coffee production area, coffee growers were located and interviewed. Each farm was sampled (1,000 sq meters plots) up to 5 acres or 2 plots for larger farms. In each plot, tree species were identified, measured for diameter at breast high (DBH) and tree high estimated. Plots were georeferenciated with GPS, and located in a GIS map, to correlate with soil map and altitude. Climatic data, potential plant growth estimates and soil characteristics were combined to produce a coffee agro-ecozoning map.

    Objective 2: The amount of N recycled by litter fall was evaluated at three locations, where plots at sun-grown, shaded and a nearby forest were established. As expected, shaded coffee added more N to the soil, although forest litter was generally even larger. Laboratory and field soil samples were used to measure N mineralization and nitrification. The results also confirm that soil under shaded legume trees provides more nitrate for coffee.
    Initial estimates of field biological N fixation by soil, leaves and lichens appear low, but natural 15N enrichment data demonstrate that Inga vera is fixing N2 under field conditions.
    Seeds of the available 30 nitrogen-fixing species were evaluated in greenhouse experiments in two representative soils. Plant height and dry weight, nodule number and weight, and nitrogenase activity (ARA) were measured. The best species were: Enterolobium cyclocarpum, Albizia lebbeck and Inga spectabilis among the Mimosoideae, and Erythrina variegata, Clitoria fairchildiana and Pterocrapus officinalis among the Papilinoideae species. Results were included in Manuel Santana’s MS thesis.

    Another greenhouse experiment obtained a similar ranking, and it suggests that most tropical legume trees tested do not respond to lime and fertilizers.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.