Ricardo O. Russo

Nitrogen-fixing trees and nitrogen fixation in sustainable agriculture : Research challenges

Abstract Research on nitrogen fixation tends to become more carefully targeted, and covers not only biological but also social and cultural aspects to achieve sustainability. However, many issues remain unsolved, such as improving N 2 uptake and the delivery mechanisms, the influence of free nitrogen in the soil and its influence on nodulation. The importance of analysing traditional field practices by farmers is stressed with examples from Mexico and Costa Rica involving Leucaena, Alnus acuminata and Erythrina spp. The case of E. poeppigiana , widely propagated by large cuttings as a shade tree for coffee where it is drastically pollarded twice a year, is described and analysed. Apparently the practice provides considerable benefits to the soil and associated crops. Erythrina spp. also show promise as nurse trees to favour nearby planted timber trees. These and other examples lend themselves to promising research projects.

Organic Foliar Fertilizer Prepared from Fermented Fruits on Growth of Vochysia guatemalensis in the Costa Rican Humid Tropics

ABSTRACT This note examines the effects of an organic foliar fertilizer prepared from fermented waste fruits on the growth of a tropical tree (Vochysia guatemalensis) under nursery conditions in the Costa Rican Humid Tropics. Results from this single experiment revealed a positive response to the foliar application of this organic fertilizer for seven out of ten evaluated variables. Root fresh weight was the most responsive with an increment of 64% over the control, followed by leaf area (50% plus), leaf fresh weight (48% plus) and leaf dry weight (46% plus). Height, diameter, and stem dry weight were also 21%, 29% and 45% higher (P < 0.05) than the control, respectively. Leaf number, and stem fresh and dry weight were not significantly different between the treated plants and the control. Based on these results, it is concluded that the fermented fruit waste solution may be used as a foliar spray to promote growth of leaf and root biomass in nursery seedlings, and may be a valuable fertilization resource in organic agriculture after testing its effects on different crops under different conditions.

Children’s Participation in the Evaluation of Bio-Indicators of Water Quality in Rural Communities

The management of bioindicators of water quality in rural communities emphasizes the importance of enabling organized groups to evaluate the quality of water resources through apprenticeship and execution of sampling methods of macro-invertebrates (biomonitoring), that can be complemented with an evaluation of physical-chemical analysis properties (pH, COD, DBO, T, BOD) of the aquatic environment. This study seeks to address childrens participation in environmental issues, and explores a new tool for evaluating water quality. With the participation of school children of Las Mercedes School and students of Guacimo High School, samples were taken using the biomonitoring BMWP’-CR (Biological Monitoring Working Party, modified for Costa Rica), index to determine the water quality of two communities in the Caribbean region of Costa Rica. The most abundant macroinvertebrates present in the samples were: Trichoptera, Coleoptera, Ephemeroptera, Odonata, Plecoptera and Hemiptera. During the collection of macro-invertebrate samples, specimens from the Perlidae family were encountered, this family being a bioindicator of excellent water quality. During the practice the school-children communities developed an environmental conscience, organization abilities, and the assimilation of the technique in the community water resources evaluation process.

Performance of Klinki (Araucaria hunsteinii K. Schuman) in the Humid Tropics of Costa Rica

Abstract Araucaria hunsteinii K. Schuman (Syn. A. klinki Lauterbach), locally known as Klinki, is a tropical conifer from Papua New Guinea, which was introduced to Costa Rica in 1966 by the Tropical Agriculture Research and Training Center (CATTE). Due to its capacity for carbon sequestration and long-term storage, and wood production, EARTH University, located in the Atlantic lowlands of Costa Rica, established two research plots with the species in October 1993 to monitor its growth in the humid tropical lowland conditions. Results show that the species performs well under such soil and climate conditions. It seems probable that Klinki may be considered as a promising species for commercial timber production and for long-term carbon sequestration in the tropics.