Developing legume shade trees for Sustainable coffee production in Puerto Rico
Coffee production in Puerto Rico is located in the central mountain region, mostly on acid, highly erodible soils. Due to several factors like labor costs, hurricanes destruction and high costs of agrochemicals, production has declined. Many small and medium scale farmers have limited resources and use questionable practices. Long-term, sustainable coffee production using environmentally sound practices should include shade trees and, if possible, fast-growing, nitrogen fixing trees (FGNFT). In an effort to increase coffee production, sun grown coffee was promoted by the Agriculture Department in the 1960’s. Unfortunately, this system of production requires high inputs and is environmentally harmful. To help coffee farmers, we will determine the best agroecological zone, evaluate legume trees species with potential for shade use, and determine management alternatives for high-quality, sustainable coffee production.
Objective 1. Survey present coffee production systems used by farmers in Puerto Rico
During the past year the field work, 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 zoning map. Results were presented at scientific meetings and the draft of a publication to be submitted to Agroforestry Systems is at its final stage. Due to its extensive details, the information concerning coffee agrozoning in Puerto Rico will be prepared for publication as an Agricultural Experimental Station Bulletin.
Objective 2. Evaluate the potential value of fast growing nitrogen fixing trees for the production of shade coffee.
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. Data have been statistically analyzed and results were included in Manuel Santana’s MS thesis presented during the past year.
Using the coffee farmer’s database compiled previously, field trips to all larger coffee producing municipalities and neighborhoods were taken. Over 110 farmers with shaded coffee have been sampled. Results indicate that more than 63 species (IVI, Index of Value Importance) with DBH> 10 cm are present. The predominant species found were Inga vera, Citrus sp., and Andira inermis, with 33.7%, 11.3% and 9.1% of IVI, respectively. The values for basal area (BA) were 36.5%, 5.8% and 7.0% in that order. The correlation between basal area and crown area (CA) was highly significant (r=0.48, P<0.0001). Clearly, coffee farmers select legume trees for shade and include a fruit species for additional income. However, diversity of the shade trees is very low and other species should be planted in the future for further sustainability of the ecosystem.
Data for climate (Puerto Rico Climate Center) and soils of Puerto Rico (USDA-NRCS) were obtained, digitized and prepared as excel data tables. A map with agroecozones for coffee production was developed by adding optimum ecological layers, soils and appropriate information using ArcGIS (v.9.1). The new map will substitute the present imprecise map of the coffee producing area, and could be used to give more incentives to farmers located in the best zone for coffee production. Management options for farmers (amount of shade, fertilization, tree species, etc) can also be deduced from this map. The information needs to be made available to farmers, planning agencies, extension agents and other scientists. Results were presented at the Sustainable Coffee Forum (May, 2007) and extended abstract published in the proceedings.
The two most extensive soils from the coffee region (Los Guineos and Humatas series; Oxisol and Ultisol respectively) were selected for the greenhouse experiments. They have been analyzed and both are acid and poor in available N.
The greenhouse (6 kg of soil/pot) experiment with selected legume tree species was carried out with a reduced number of species. This objective faced some problems due to the lack of seeds, since:
1) We had to wait for seed production for many local species in order to obtain seed. For some species we have not been able to locate trees producing, or their fructifying period is unknown. To facilitate future work and seed collection, we prepared tables with species location (GPS) and the period of flowering/seed production for local trees. However, this database is still incomplete since permanent field trips all over Puerto Rico are required to obtain data. Seeds from a few other species were obtained from ECHO (Florida).
2) Some species (mostly of the genus Inga), even when harvested in the most appropriate time, are recalcitrant and don’t germinate after 2 weeks even in the best storage condition. Therefore, some of these species were included in the first, smaller experiment. For comparative purposes, seeds of Pithecellobium carbonarum (carbonero) where included as control, and they were included in every planting date. This species shows good shade characteristics, but was recorded as very susceptible to nematodes, at least in one soil. Furthermore growth is extremely slow, at least under the low altitude where our greenhouses are located. We are presently testing the use of stakes for those species (such as Inga) were seed is recalcitrant or not available. The species that were harvested earlier (first experiment with recalcitrant seeds, genus Inga) were analyzed by Kjeldahl to estimate the amount of N fixed. The results have been included in Manuel Santana’s MS thesis, presented during the past semester.
The gas chromatograph (used the ARA analysis) purchased with the project funds is presently extensively used to evaluate N fixation and ethylene production. In fact, recently the air cylinder was empty, and all cylinders (air, hydrogen and nitrogen) are undergoing safety testing and refilling. We have been able to continue work by cooperating with the Horticulture Department who provided gas cylinders.
Since Soil N mineralization studies, field estimates of N fixation and effect of pH and nutrients on NFT’s growth are still undergoing, we estimate that to complete the project, an extension without additional funds will be required.
Impacts and Contributions/Outcomes
1. A WEB page about the project (link to SARE) is available in the INTERNET at:
A complementary web page in Spanish, more accessible for farmers and with more practical information was also prepared, and it can be found at:
This page will be more frequently updated and include recent news and future activities. Since a new pest, the coffee berry borer or “broca” (Hypothenemus hampei) appeared in Puerto Rico in July 2007, biological control methods will be very important for control, and web pages very important to disseminate new information.
2. Two graduate students initiated their M.S. studies in January 2006 their MS and they are conducting their thesis within the SARE LS04-162 PROJECT (Glenny López, from the Dominican Republic and Ixia A. Avilés from Puerto Rico). More recently, Feliciano Andujar (Dominican Republic), started his studies or an MS degree and will participate in the project by expanding the number of species tested for ARA and evaluate which soil factors limit biological nitrogen fixation. During this project, a total of 5 graduate students will obtain their M.S. degrees and trained in the production of sustainable coffee.
3. Data and results from the project have been presented at:
a) Foro sobre Café Sostenible en Puerto Rico (Mayagüez, PR, May 30, 2007),
b) First Conservation and Agroforestry Forum (UPR Utuado, 11 April 2008)
c) Sigma Xi Scientific Society Poster Day. Mayagüez, April 10, 2008.
An exhibit about Sustainable coffee production and legume trees was displayed at the Agricultural students Agricultural Fair (5 Days with our Land, March, 2008).
A major accomplishment of the project was the organization and completion of the Sustainable Coffee Forum in May 30th, 2007 (as proposed in the grant). The Forum was extremely successful, and many scientists, graduate students, extension agents, Natural Resources and Agricultural Department personnel and some coffee farmers participated in this Forum. A publication (printed and CD) with extended abstracts of the presentations was produced and widely distributed to libraries and interested Institutions and individuals. Some copies are still available and freely supplied to interested persons.
The major project outcome will be:
1) Identification of the best area for growing coffee in Puerto Rico (ecozoning),
2) Establish the potential of 30 legume tree species for supplying N for coffee, and
3) Farmers and extension agents will be able to select the best shade tree species for each soil and altitude.
However, due to the slow initial start and some of the administrative and scientific problems, and to complete 3 undergoing MS research thesis and prepare publications, a 6 month extension of the grant (with no additional funds) is necessary.
Agricultural Experiment Station
HC-01 Box 4508
Adjuntas, PR 00601-9717
Office Phone: 7878290012
Sustainable Agriculture Coordinator
University of Puerto Rico
Agricultural Extension Service
Department of Agricultural Economics
Mayagüez, PR 00681-9030
Office Phone: 7878324040
Agricultural Extension Service
University of Puerto Rico
PO Box 9030
Mayagüez, PR 00681
Office Phone: 7872654130